diff --git a/demos/autocomplete/maxheight.html b/demos/autocomplete/maxheight.html
index 9ebda7938..b8c59819d 100644
--- a/demos/autocomplete/maxheight.html
+++ b/demos/autocomplete/maxheight.html
@@ -13,12 +13,6 @@
 		/* prevent horizontal scrollbar */
 		overflow-x: hidden;
 	}
-	/* IE 6 doesn't support max-height
-	 * we use height instead, but this forces the menu to always be this tall
-	 */
-	* html .ui-autocomplete {
-		height: 100px;
-	}
 	</style>
 	<script src="../../external/requirejs/require.js"></script>
 	<script src="../bootstrap.js">
diff --git a/demos/bootstrap.js b/demos/bootstrap.js
index 9b0468028..ba1cde2e9 100644
--- a/demos/bootstrap.js
+++ b/demos/bootstrap.js
@@ -2,9 +2,7 @@
 ( function() {
 "use strict";
 
-// Find the script element
-var scripts = document.getElementsByTagName( "script" );
-var script = scripts[ scripts.length - 1 ];
+var script = document.currentScript;
 
 // Read the modules
 var modules = script.getAttribute( "data-modules" );
diff --git a/demos/tooltip/custom-style.html b/demos/tooltip/custom-style.html
index 5cbd4bbd3..8ab8dcc9d 100644
--- a/demos/tooltip/custom-style.html
+++ b/demos/tooltip/custom-style.html
@@ -60,8 +60,6 @@
 		width: 25px;
 		height: 25px;
 		box-shadow: 6px 5px 9px -9px black;
-		-webkit-transform: rotate(45deg);
-		-ms-transform: rotate(45deg);
 		transform: rotate(45deg);
 	}
 	.arrow.top:after {
diff --git a/tests/lib/qunit-assert-domequal.js b/tests/lib/qunit-assert-domequal.js
index bcce60702..d99ed06de 100644
--- a/tests/lib/qunit-assert-domequal.js
+++ b/tests/lib/qunit-assert-domequal.js
@@ -83,17 +83,6 @@ function getElementStyles( elem ) {
 		key = style[ len ];
 		camelKey = camelCase( key );
 
-		// Support: IE <=11+
-		// In IE, `option` elements may have different initial `option` colors.
-		// They may initially all be transparent, but later the selected
-		// option gets a blue background with white text; ignore it.
-		if ( document.documentMode && elem.nodeName.toLowerCase() === "option" && (
-			camelKey === "color" ||
-				camelKey.indexOf( "Color" ) === camelKey.length - "Color".length
-		) ) {
-			continue;
-		}
-
 		if ( typeof style[ key ] === "string" ) {
 			styles[ camelKey ] = style[ key ];
 		}
diff --git a/tests/lib/vendor/qunit-composite/qunit-composite.js b/tests/lib/vendor/qunit-composite/qunit-composite.js
index 042d024b4..b3c2b749d 100644
--- a/tests/lib/vendor/qunit-composite/qunit-composite.js
+++ b/tests/lib/vendor/qunit-composite/qunit-composite.js
@@ -35,9 +35,6 @@ function addEvent( elem, type, fn ) {
 	if ( elem.addEventListener ) {
 		// Standards-based browsers
 		elem.addEventListener( type, fn, false );
-	} else if ( elem.attachEvent ) {
-		// support: IE <9
-		elem.attachEvent( "on" + type, fn );
 	}
 }
 
diff --git a/tests/unit/autocomplete/events.js b/tests/unit/autocomplete/events.js
index d08fe9828..9ee3a92e4 100644
--- a/tests/unit/autocomplete/events.js
+++ b/tests/unit/autocomplete/events.js
@@ -75,11 +75,7 @@ $.each( [
 			assert.ok( menu.is( ":visible" ), "menu is visible after delay" );
 			element.simulate( "keydown", { keyCode: $.ui.keyCode.DOWN } );
 			element.simulate( "keydown", { keyCode: $.ui.keyCode.ENTER } );
-
-			// Blur must be async for IE to handle it properly
-			setTimeout( function() {
-				element.simulate( "blur" );
-			} );
+			element.simulate( "blur" );
 		} );
 	} );
 } );
diff --git a/tests/unit/button/core.js b/tests/unit/button/core.js
index 7b696631e..ae4b870ed 100644
--- a/tests/unit/button/core.js
+++ b/tests/unit/button/core.js
@@ -2,7 +2,6 @@ define( [
 	"qunit",
 	"jquery",
 	"lib/helper",
-	"ui/safe-active-element",
 	"ui/widgets/button"
 ], function( QUnit, $, helper ) {
 "use strict";
@@ -17,10 +16,10 @@ QUnit.test( "Disabled button loses focus", function( assert ) {
 	element.trigger( "focus" );
 	setTimeout( function() {
 
-		assert.equal( element[ 0 ], $.ui.safeActiveElement( document ), "Button is focused" );
+		assert.equal( element[ 0 ], document.activeElement, "Button is focused" );
 
 		element.button( "disable" );
-		assert.notEqual( element[ 0 ], $.ui.safeActiveElement( document ), "Button has had focus removed" );
+		assert.notEqual( element[ 0 ], document.activeElement, "Button has had focus removed" );
 		ready();
 	} );
 } );
diff --git a/tests/unit/checkboxradio/core.js b/tests/unit/checkboxradio/core.js
index ad27f1be0..f218cc1cd 100644
--- a/tests/unit/checkboxradio/core.js
+++ b/tests/unit/checkboxradio/core.js
@@ -33,7 +33,6 @@ QUnit.test( "Radios - Initial class structure", function( assert ) {
 } );
 
 QUnit.test( "Ensure checked after single click on checkbox label button", function( assert ) {
-	var ready = assert.async();
 	assert.expect( 2 );
 
 	$( "#check2" ).checkboxradio().on( "change", function() {
@@ -43,14 +42,7 @@ QUnit.test( "Ensure checked after single click on checkbox label button", functi
 		assert.hasClasses( label, "ui-state-active" );
 	} );
 
-	// Support: Opera
-	// Opera doesn't trigger a change event when this is done synchronously.
-	// This seems to be a side effect of another test, but until that can be
-	// tracked down, this delay will have to do.
-	setTimeout( function() {
-		$( "#check2" ).checkboxradio( "widget" ).simulate( "click" );
-		ready();
-	} );
+	$( "#check2" ).checkboxradio( "widget" ).simulate( "click" );
 } );
 
 QUnit.test( "Handle form association via form attribute", function( assert ) {
diff --git a/tests/unit/core/core.js b/tests/unit/core/core.js
index d9677a406..5d9eee07c 100644
--- a/tests/unit/core/core.js
+++ b/tests/unit/core/core.js
@@ -3,7 +3,6 @@ define( [
 	"jquery",
 	"lib/common",
 	"lib/helper",
-	"ui/form",
 	"ui/labels",
 	"ui/unique-id"
 ], function( QUnit, $, common, helper ) {
@@ -150,10 +149,6 @@ QUnit.test( "Labels", function( assert ) {
 	function testLabels( testType ) {
 		var labels = dom.find( "#test" ).labels();
 		var found = labels.map( function() {
-
-				// Support: Core 1.9 Only
-				// We use String.prototype.trim because core 1.9.x silently fails
-				// when white space is present
 				return String.prototype.trim.call( $( this ).text() );
 			} ).get();
 
@@ -183,7 +178,7 @@ QUnit.test( "Labels", function( assert ) {
 			QUnit.test( name + this.id.replace( /_/g, " " ), function( assert ) {
 				var ready = assert.async();
 				assert.expect( 1 );
-				var form = input._form();
+				var form = $( input.prop( "form" ) );
 
 				// If input has a form the value should reset to "" if not it should be "changed"
 				var value = form.length ? "" : "changed";
diff --git a/tests/unit/datepicker/core.js b/tests/unit/datepicker/core.js
index 74320931e..edc16d005 100644
--- a/tests/unit/datepicker/core.js
+++ b/tests/unit/datepicker/core.js
@@ -311,9 +311,6 @@ QUnit.test( "customStructure", function( assert ) {
 		} );
 	}
 
-	// TODO: figure out why this setTimeout is needed in IE,
-	// it only is necessary when the previous baseStructure tests runs first
-	// Support: IE
 	setTimeout( step1 );
 } );
 
diff --git a/tests/unit/datepicker/options.js b/tests/unit/datepicker/options.js
index 5d03cd61f..3055bc199 100644
--- a/tests/unit/datepicker/options.js
+++ b/tests/unit/datepicker/options.js
@@ -5,8 +5,7 @@ define( [
 	"ui/widgets/datepicker",
 	"ui/i18n/datepicker-fr",
 	"ui/i18n/datepicker-he",
-	"ui/i18n/datepicker-zh-CN",
-	"ui/ie"
+	"ui/i18n/datepicker-zh-CN"
 ], function( QUnit, $, testHelper ) {
 "use strict";
 
@@ -97,147 +96,131 @@ QUnit.test( "change", function( assert ) {
 	assert.equal( $.datepicker._defaults.showOn, "focus", "Retain default showOn" );
 } );
 
-( function() {
-	var url = window.location.search;
-	url = decodeURIComponent( url.slice( url.indexOf( "swarmURL=" ) + 9 ) );
+QUnit.test( "invocation", function( assert ) {
+	var ready = assert.async();
+	var button, image,
+		body = $( "body" );
 
-	// TODO: This test occassionally fails in IE in TestSwarm
-	if ( $.ui.ie && url && url.indexOf( "http" ) === 0 ) {
-		return;
+	assert.expect( 29 );
+
+	function step0() {
+		var inp = testHelper.initNewInput(),
+			dp = $( "#ui-datepicker-div" );
+
+		button = inp.siblings( "button" );
+		assert.ok( button.length === 0, "Focus - button absent" );
+		image = inp.siblings( "img" );
+		assert.ok( image.length === 0, "Focus - image absent" );
+
+		testHelper.onFocus( inp, function() {
+			assert.ok( dp.is( ":visible" ), "Focus - rendered on focus" );
+			inp.simulate( "keydown", { keyCode: $.ui.keyCode.ESCAPE } );
+			assert.ok( !dp.is( ":visible" ), "Focus - hidden on exit" );
+			step1();
+		} );
 	}
 
-	QUnit.test( "invocation", function( assert ) {
-		var ready = assert.async();
-		var button, image,
-			isOldIE = $.ui.ie && ( !document.documentMode || document.documentMode < 9 ),
-			body = $( "body" );
+	function step1() {
 
-		assert.expect( isOldIE ? 25 : 29 );
+		var inp = testHelper.initNewInput(),
+			dp = $( "#ui-datepicker-div" );
 
-		function step0() {
-			var inp = testHelper.initNewInput(),
-				dp = $( "#ui-datepicker-div" );
+		testHelper.onFocus( inp, function() {
+			assert.ok( dp.is( ":visible" ), "Focus - rendered on focus" );
+			body.simulate( "mousedown", {} );
+			assert.ok( !dp.is( ":visible" ), "Focus - hidden on external click" );
+			inp.datepicker( "hide" ).datepicker( "destroy" );
 
-			button = inp.siblings( "button" );
-			assert.ok( button.length === 0, "Focus - button absent" );
-			image = inp.siblings( "img" );
-			assert.ok( image.length === 0, "Focus - image absent" );
+			step2();
+		} );
+	}
 
-			testHelper.onFocus( inp, function() {
-				assert.ok( dp.is( ":visible" ), "Focus - rendered on focus" );
-				inp.simulate( "keydown", { keyCode: $.ui.keyCode.ESCAPE } );
-				assert.ok( !dp.is( ":visible" ), "Focus - hidden on exit" );
-				step1();
-			} );
-		}
+	function step2() {
+		var inp = testHelper.initNewInput( {
+				showOn: "button",
+				buttonText: "Popup"
+			} ),
+			dp = $( "#ui-datepicker-div" );
 
-		function step1() {
+		assert.ok( !dp.is( ":visible" ), "Button - initially hidden" );
+		button = inp.siblings( "button" );
+		image = inp.siblings( "img" );
+		assert.ok( button.length === 1, "Button - button present" );
+		assert.ok( image.length === 0, "Button - image absent" );
+		assert.equal( button.text(), "Popup", "Button - button text" );
 
-			var inp = testHelper.initNewInput(),
-				dp = $( "#ui-datepicker-div" );
+		testHelper.onFocus( inp, function() {
+			assert.ok( !dp.is( ":visible" ), "Button - not rendered on focus" );
+			button.trigger( "click" );
+			assert.ok( dp.is( ":visible" ), "Button - rendered on button click" );
+			button.trigger( "click" );
+			assert.ok( !dp.is( ":visible" ), "Button - hidden on second button click" );
+			inp.datepicker( "hide" ).datepicker( "destroy" );
 
-			testHelper.onFocus( inp, function() {
-				assert.ok( dp.is( ":visible" ), "Focus - rendered on focus" );
-				body.simulate( "mousedown", {} );
-				assert.ok( !dp.is( ":visible" ), "Focus - hidden on external click" );
-				inp.datepicker( "hide" ).datepicker( "destroy" );
+			step3();
+		} );
+	}
 
-				step2();
-			} );
-		}
+	function step3() {
+		var inp = testHelper.initNewInput( {
+				showOn: "button",
+				buttonImageOnly: true,
+				buttonImage: "images/calendar.gif",
+				buttonText: "Cal"
+			} ),
+			dp = $( "#ui-datepicker-div" );
 
-		function step2() {
-			var inp = testHelper.initNewInput( {
-					showOn: "button",
-					buttonText: "Popup"
-				} ),
-				dp = $( "#ui-datepicker-div" );
+		assert.ok( !dp.is( ":visible" ), "Image button - initially hidden" );
+		button = inp.siblings( "button" );
+		assert.ok( button.length === 0, "Image button - button absent" );
+		image = inp.siblings( "img" );
+		assert.ok( image.length === 1, "Image button - image present" );
+		assert.ok( /images\/calendar\.gif$/.test( image.attr( "src" ) ), "Image button - image source" );
+		assert.equal( image.attr( "title" ), "Cal", "Image button - image text" );
 
-			assert.ok( !dp.is( ":visible" ), "Button - initially hidden" );
-			button = inp.siblings( "button" );
-			image = inp.siblings( "img" );
-			assert.ok( button.length === 1, "Button - button present" );
-			assert.ok( image.length === 0, "Button - image absent" );
-			assert.equal( button.text(), "Popup", "Button - button text" );
+		testHelper.onFocus( inp, function() {
+			assert.ok( !dp.is( ":visible" ), "Image button - not rendered on focus" );
+			image.trigger( "click" );
+			assert.ok( dp.is( ":visible" ), "Image button - rendered on image click" );
+			image.trigger( "click" );
+			assert.ok( !dp.is( ":visible" ), "Image button - hidden on second image click" );
+			inp.datepicker( "hide" ).datepicker( "destroy" );
 
-			testHelper.onFocus( inp, function() {
-				assert.ok( !dp.is( ":visible" ), "Button - not rendered on focus" );
-				button.trigger( "click" );
-				assert.ok( dp.is( ":visible" ), "Button - rendered on button click" );
-				button.trigger( "click" );
-				assert.ok( !dp.is( ":visible" ), "Button - hidden on second button click" );
-				inp.datepicker( "hide" ).datepicker( "destroy" );
+			step4();
+		} );
+	}
 
-				step3();
-			} );
-		}
+	function step4() {
+		var inp = testHelper.initNewInput( {
+				showOn: "both",
+				buttonImage: "images/calendar.gif"
+			} ),
+			dp = $( "#ui-datepicker-div" );
 
-		function step3() {
-			var inp = testHelper.initNewInput( {
-					showOn: "button",
-					buttonImageOnly: true,
-					buttonImage: "images/calendar.gif",
-					buttonText: "Cal"
-				} ),
-				dp = $( "#ui-datepicker-div" );
+		assert.ok( !dp.is( ":visible" ), "Both - initially hidden" );
+		button = inp.siblings( "button" );
+		assert.ok( button.length === 1, "Both - button present" );
+		image = inp.siblings( "img" );
+		assert.ok( image.length === 0, "Both - image absent" );
+		image = button.children( "img" );
+		assert.ok( image.length === 1, "Both - button image present" );
 
-			assert.ok( !dp.is( ":visible" ), "Image button - initially hidden" );
-			button = inp.siblings( "button" );
-			assert.ok( button.length === 0, "Image button - button absent" );
-			image = inp.siblings( "img" );
-			assert.ok( image.length === 1, "Image button - image present" );
-			assert.ok( /images\/calendar\.gif$/.test( image.attr( "src" ) ), "Image button - image source" );
-			assert.equal( image.attr( "title" ), "Cal", "Image button - image text" );
+		testHelper.onFocus( inp, function() {
+			assert.ok( dp.is( ":visible" ), "Both - rendered on focus" );
+			body.simulate( "mousedown", {} );
+			assert.ok( !dp.is( ":visible" ), "Both - hidden on external click" );
+			button.trigger( "click" );
+			assert.ok( dp.is( ":visible" ), "Both - rendered on button click" );
+			button.trigger( "click" );
+			assert.ok( !dp.is( ":visible" ), "Both - hidden on second button click" );
+			inp.datepicker( "hide" ).datepicker( "destroy" );
 
-			testHelper.onFocus( inp, function() {
-				assert.ok( !dp.is( ":visible" ), "Image button - not rendered on focus" );
-				image.trigger( "click" );
-				assert.ok( dp.is( ":visible" ), "Image button - rendered on image click" );
-				image.trigger( "click" );
-				assert.ok( !dp.is( ":visible" ), "Image button - hidden on second image click" );
-				inp.datepicker( "hide" ).datepicker( "destroy" );
+			ready();
+		} );
+	}
 
-				step4();
-			} );
-		}
-
-		function step4() {
-			var inp = testHelper.initNewInput( {
-					showOn: "both",
-					buttonImage: "images/calendar.gif"
-				} ),
-				dp = $( "#ui-datepicker-div" );
-
-			assert.ok( !dp.is( ":visible" ), "Both - initially hidden" );
-			button = inp.siblings( "button" );
-			assert.ok( button.length === 1, "Both - button present" );
-			image = inp.siblings( "img" );
-			assert.ok( image.length === 0, "Both - image absent" );
-			image = button.children( "img" );
-			assert.ok( image.length === 1, "Both - button image present" );
-
-			// TODO: This test occasionally fails to focus in IE8 in BrowserStack
-			if ( !isOldIE ) {
-				testHelper.onFocus( inp, function() {
-					assert.ok( dp.is( ":visible" ), "Both - rendered on focus" );
-					body.simulate( "mousedown", {} );
-					assert.ok( !dp.is( ":visible" ), "Both - hidden on external click" );
-					button.trigger( "click" );
-					assert.ok( dp.is( ":visible" ), "Both - rendered on button click" );
-					button.trigger( "click" );
-					assert.ok( !dp.is( ":visible" ), "Both - hidden on second button click" );
-					inp.datepicker( "hide" ).datepicker( "destroy" );
-
-					ready();
-				} );
-			} else {
-				ready();
-			}
-		}
-
-		step0();
-	} );
-} )();
+	step0();
+} );
 
 QUnit.test( "otherMonths", function( assert ) {
 	assert.expect( 8 );
diff --git a/tests/unit/dialog/core.js b/tests/unit/dialog/core.js
index cb0ee53e0..d307504b8 100644
--- a/tests/unit/dialog/core.js
+++ b/tests/unit/dialog/core.js
@@ -103,12 +103,6 @@ QUnit.test( "focus tabbable", function( assert ) {
 		};
 
 	function checkFocus( markup, options, testFn, next ) {
-
-		// Support: IE8
-		// For some reason the focus doesn't get set properly if we don't
-		// focus the body first.
-		$( "body" ).trigger( "focus" );
-
 		element = $( markup ).dialog( options );
 		setTimeout( function() {
 			testFn( function done() {
@@ -122,31 +116,12 @@ QUnit.test( "focus tabbable", function( assert ) {
 		checkFocus( "<div><input><input></div>", options, function( done ) {
 			var input = element.find( "input" ).last().trigger( "focus" ).trigger( "blur" );
 
-			// Support: IE 11+
-			// In IE in jQuery 3.4+ a sequence:
-			// $( inputNode ).trigger( "focus" ).trigger( "blur" ).trigger( "focus" )
-			// doesn't end up with a focused input. See:
-			// https://github.com/jquery/jquery/issues/4856
-			// However, in this test we only want to check that the last focused
-			// input receives the focus back when `_focusTabbable()` is called
-			// which in reality doesn't happen so quickly so let's avoid the issue
-			// by waiting a bit.
-			if ( document.documentMode ) {
-				setTimeout( function() {
-					focusTabbableAndAssert();
-				}, 500 );
-			} else {
-				focusTabbableAndAssert();
-			}
-
-			function focusTabbableAndAssert() {
-				element.dialog( "instance" )._focusTabbable();
-				setTimeout( function() {
-					assert.equal( document.activeElement, input[ 0 ],
-						"1. an element that was focused previously." );
-					done();
-				} );
-			}
+			element.dialog( "instance" )._focusTabbable();
+			setTimeout( function() {
+				assert.equal( document.activeElement, input[ 0 ],
+					"1. an element that was focused previously." );
+				done();
+			} );
 		}, step2 );
 	}
 
@@ -303,11 +278,6 @@ QUnit.test( "interaction between overlay and other dialogs", function( assert )
 		second = $( "<div><input id='input-2'></div>" ).testWidget(),
 		secondInput = second.find( "input" );
 
-	// Support: IE8
-	// For some reason the focus doesn't get set properly if we don't
-	// focus the body first.
-	$( "body" ).trigger( "focus" );
-
 	// Wait for the modal to init
 	setTimeout( function() {
 
diff --git a/tests/unit/dialog/methods.js b/tests/unit/dialog/methods.js
index 1de32194b..c3f360fb9 100644
--- a/tests/unit/dialog/methods.js
+++ b/tests/unit/dialog/methods.js
@@ -226,11 +226,6 @@ QUnit.test( "#8958: dialog can be opened while opening", function( assert ) {
 		}
 	} );
 
-	// Support: IE8
-	// For some reason the #favorite-animal input doesn't get focus if we don't
-	// focus the body first, causing the test to hang.
-	$( "body" ).trigger( "focus" );
-
 	$( "#favorite-animal" )
 
 		// We focus the input to start the test. Once it receives focus, the
diff --git a/tests/unit/draggable/core.js b/tests/unit/draggable/core.js
index 46c856d4e..d7f786c93 100644
--- a/tests/unit/draggable/core.js
+++ b/tests/unit/draggable/core.js
@@ -38,8 +38,8 @@ QUnit.test( "element types", function( assert ) {
 		} );
 		offsetAfter = el.offset();
 
-		// Support: FF, Chrome, and IE9,
-		// there are some rounding errors in so we can't say equal, we have to settle for close enough
+		// Support: Firefox, Chrome
+		// There are some rounding errors, so we can't say equal, we have to settle for close enough
 		assert.close( offsetBefore.left, offsetAfter.left - 50, 1, "dragged[50, 50] " + "<" + typeName + "> left" );
 		assert.close( offsetBefore.top, offsetAfter.top - 50, 1, "dragged[50, 50] " + "<" + typeName + "> top" );
 		el.draggable( "destroy" );
@@ -112,7 +112,6 @@ QUnit.test( "Stray mousemove after mousedown still drags", function( assert ) {
 
 	// In IE8, when content is placed under the mouse (e.g. when draggable content is replaced
 	// on mousedown), mousemove is triggered on those elements even though the mouse hasn't moved.
-	// Support: IE <9
 	element.on( "mousedown", function() {
 		$( document ).simulate( "mousemove", { button: -1 } );
 	} );
@@ -341,11 +340,13 @@ QUnit.test( "blur behavior - off handle", function( assert ) {
 	var element = $( "#draggable2" ).draggable( { handle: "span" } ),
 		focusElement = $( "<div tabindex='1'></div>" ).appendTo( element );
 
-	// Mock $.ui.safeBlur with a spy
-	var _safeBlur = $.ui.safeBlur;
+	// Mock $.ui.trigger with a spy
+	var _trigger = $.fn.trigger;
 	var blurCalledCount = 0;
-	$.ui.safeBlur = function() {
-		blurCalledCount++;
+	$.fn.trigger = function( eventName ) {
+		if ( eventName === "blur" ) {
+			blurCalledCount++;
+		}
 	};
 
 	testHelper.onFocus( focusElement, function() {
@@ -357,8 +358,8 @@ QUnit.test( "blur behavior - off handle", function( assert ) {
 		testHelper.move( element.find( "span" ), 1, 1 );
 		assert.strictEqual( blurCalledCount, 1, "draggable blurs when mousing down on handle" );
 
-		// Restore safeBlur
-		$.ui.safeBlur = _safeBlur;
+		// Restore trigger
+		$.fn.trigger = _trigger;
 
 		ready();
 	} );
@@ -394,27 +395,21 @@ QUnit.test( "ui-draggable-handle managed correctly in nested draggables", functi
 	assert.hasClasses( child, "ui-draggable-handle", "child retains class name on destroy" );
 } );
 
-// Support: IE 8 only
-// IE 8 implements DOM Level 2 Events which only has events bubble up to the document.
-// We skip this test since it would be impossible for it to pass in such an environment.
-QUnit[ document.documentMode === 8 ? "skip" : "test" ](
-	"does not stop propagation to window",
-	function( assert ) {
-		assert.expect( 1 );
-		var element = $( "#draggable1" ).draggable();
+QUnit.test( "does not stop propagation to window", function( assert ) {
+	assert.expect( 1 );
+	var element = $( "#draggable1" ).draggable();
 
-		var handler = function() {
-			assert.ok( true, "mouseup propagates to window" );
-		};
-		$( window ).on( "mouseup", handler );
+	var handler = function() {
+		assert.ok( true, "mouseup propagates to window" );
+	};
+	$( window ).on( "mouseup", handler );
 
-		element.simulate( "drag", {
-			dx: 10,
-			dy: 10
-		} );
+	element.simulate( "drag", {
+		dx: 10,
+		dy: 10
+	} );
 
-		$( window ).off( "mouseup", handler );
-	}
-);
+	$( window ).off( "mouseup", handler );
+} );
 
 } );
diff --git a/tests/unit/draggable/helper.js b/tests/unit/draggable/helper.js
index 292b75bf0..2fd637a24 100644
--- a/tests/unit/draggable/helper.js
+++ b/tests/unit/draggable/helper.js
@@ -8,9 +8,6 @@ define( [
 
 return $.extend( helper, {
 
-	// TODO: remove the unreliable offset hacks
-	unreliableOffset: $.ui.ie && ( !document.documentMode || document.documentMode < 8 ) ? 2 : 0,
-
 	testDragPosition: function( assert, el, dx, dy, expectedDX, expectedDY, msg ) {
 		msg = msg ? msg + "." : "";
 
diff --git a/tests/unit/draggable/options.js b/tests/unit/draggable/options.js
index 79aac27c2..f97696920 100644
--- a/tests/unit/draggable/options.js
+++ b/tests/unit/draggable/options.js
@@ -743,11 +743,11 @@ QUnit.test( "cursorAt", function( assert ) {
 							assert.equal( ui.position.left - ui.originalPosition.left, deltaX, testName + " " + position + " left" );
 							assert.equal( ui.position.top - ui.originalPosition.top, deltaY, testName + " " + position + " top" );
 						} else if ( testData.cursorAt.right ) {
-							assert.equal( ui.helper.width() - ( event.clientX - ui.offset.left ), testData.x - testHelper.unreliableOffset, testName + " " + position + " left" );
-							assert.equal( ui.helper.height() - ( event.clientY - ui.offset.top ), testData.y - testHelper.unreliableOffset, testName + " " + position + " top" );
+							assert.equal( ui.helper.width() - ( event.clientX - ui.offset.left ), testData.x, testName + " " + position + " left" );
+							assert.equal( ui.helper.height() - ( event.clientY - ui.offset.top ), testData.y, testName + " " + position + " top" );
 						} else {
-							assert.equal( event.clientX - ui.offset.left, testData.x + testHelper.unreliableOffset, testName + " " + position + " left" );
-							assert.equal( event.clientY - ui.offset.top, testData.y + testHelper.unreliableOffset, testName + " " + position + " top" );
+							assert.equal( event.clientX - ui.offset.left, testData.x, testName + " " + position + " left" );
+							assert.equal( event.clientY - ui.offset.top, testData.y, testName + " " + position + " top" );
 						}
 					}
 			} );
@@ -785,11 +785,11 @@ QUnit.test( "cursorAt, switching after initialization", function( assert ) {
 							assert.equal( ui.position.left - ui.originalPosition.left, deltaX, testName + " " + position + " left" );
 							assert.equal( ui.position.top - ui.originalPosition.top, deltaY, testName + " " + position + " top" );
 						} else if ( testData.cursorAt.right ) {
-							assert.equal( ui.helper.width() - ( event.clientX - ui.offset.left ), testData.x - testHelper.unreliableOffset, testName + " " + position + " left" );
-							assert.equal( ui.helper.height() - ( event.clientY - ui.offset.top ), testData.y - testHelper.unreliableOffset, testName + " " + position + " top" );
+							assert.equal( ui.helper.width() - ( event.clientX - ui.offset.left ), testData.x, testName + " " + position + " left" );
+							assert.equal( ui.helper.height() - ( event.clientY - ui.offset.top ), testData.y, testName + " " + position + " top" );
 						} else {
-							assert.equal( event.clientX - ui.offset.left, testData.x + testHelper.unreliableOffset, testName + " " + position + " left" );
-							assert.equal( event.clientY - ui.offset.top, testData.y + testHelper.unreliableOffset, testName + " " + position + " top" );
+							assert.equal( event.clientX - ui.offset.left, testData.x, testName + " " + position + " left" );
+							assert.equal( event.clientY - ui.offset.top, testData.y, testName + " " + position + " top" );
 						}
 					}
 			} );
@@ -1136,15 +1136,6 @@ QUnit.test( "scroll ignores containers that are overflow: hidden", function( ass
 		dy: 1300
 	} );
 
-	// IE8 natively scrolls when dragging an element inside a overflow:hidden
-	// container, so skip this test if native scroll occurs.
-	// Support: IE <9
-	if ( scrollParent.scrollTop() > 0 ) {
-		assert.ok( true, "overflow:hidden container natively scrolls" );
-		assert.ok( true, "overflow:hidden container natively scrolls" );
-		return;
-	}
-
 	element.css( { top: 0, left: 0 } ).draggable( "option", "scroll", true );
 
 	element.simulate( "drag", {
@@ -1458,7 +1449,7 @@ QUnit.test( "zIndex, default, switching after initialization", function( assert
 } );
 
 QUnit.test( "iframeFix", function( assert ) {
-	assert.expect( 6 );
+	assert.expect( 5 );
 
 	var element = $( "<div>" ).appendTo( "#qunit-fixture" ).draggable( { iframeFix: true } ),
 		element2 = $( "<div>" ).appendTo( "#qunit-fixture" ).draggable( { iframeFix: ".iframe" } ),
@@ -1474,8 +1465,7 @@ QUnit.test( "iframeFix", function( assert ) {
 	} );
 
 	element.one( "drag", function() {
-		var divOffset, iframeOffset,
-			div = $( this ).children().not( "iframe" );
+		var div = $( this ).children().not( "iframe" );
 
 		// https://bugs.jqueryui.com/ticket/9671
 		// iframeFix doesn't handle iframes that move
@@ -1483,13 +1473,7 @@ QUnit.test( "iframeFix", function( assert ) {
 		assert.equal( div.outerWidth(), iframe.outerWidth(), "blocking div is wide enough" );
 		assert.equal( div.outerHeight(), iframe.outerHeight(), "blocking div is tall enough" );
 
-		divOffset = div.offset();
-		iframeOffset = iframe.offset();
-
-		// Support: Edge <79 only
-		// In Edge Legacy these values differ a little.
-		assert.ok( Math.abs( divOffset.top - iframeOffset.top ) < 0.25, "Check top within 0.25 of expected" );
-		assert.ok( Math.abs( divOffset.left - iframeOffset.left ) < 0.25, "Check left within 0.25 of expected" );
+		assert.deepEqual( div.offset(), iframe.offset(), "blocking div is tall enough" );
 	} );
 
 	element.simulate( "drag", {
diff --git a/tests/unit/menu/events.js b/tests/unit/menu/events.js
index caac7e741..f03ba333c 100644
--- a/tests/unit/menu/events.js
+++ b/tests/unit/menu/events.js
@@ -54,17 +54,11 @@ QUnit.test( "handle click on custom item menu", function( assert ) {
 QUnit.test( "handle blur", function( assert ) {
 	var ready = assert.async();
 	assert.expect( 2 );
-	var blurHandled = false,
-		index = 1,
+	var index = 1,
 		element = $( "#menu1" ).menu( {
 			blur: function( event, ui ) {
-
-				// Ignore duplicate blur event fired by IE
-				if ( !blurHandled ) {
-					blurHandled = true;
-					assert.equal( event.type, "menublur", "blur event.type is 'menublur'" );
-					assert.strictEqual( ui.item[ 0 ], element.children()[ index ], "ui.item" );
-				}
+				assert.equal( event.type, "menublur", "blur event.type is 'menublur'" );
+				assert.strictEqual( ui.item[ 0 ], element.children()[ index ], "ui.item" );
 			}
 		} );
 
@@ -80,17 +74,11 @@ QUnit.test( "handle blur", function( assert ) {
 QUnit.test( "handle blur via click outside", function( assert ) {
 	var ready = assert.async();
 	assert.expect( 2 );
-	var blurHandled = false,
-		index = 1,
+	var index = 1,
 		element = $( "#menu1" ).menu( {
 			blur: function( event, ui ) {
-
-				// Ignore duplicate blur event fired by IE
-				if ( !blurHandled ) {
-					blurHandled = true;
-					assert.equal( event.type, "menublur", "blur event.type is 'menublur'" );
-					assert.strictEqual( ui.item[ 0 ], element.children()[ index ], "ui.item" );
-				}
+				assert.equal( event.type, "menublur", "blur event.type is 'menublur'" );
+				assert.strictEqual( ui.item[ 0 ], element.children()[ index ], "ui.item" );
 			}
 		} );
 
diff --git a/tests/unit/sortable/options.js b/tests/unit/sortable/options.js
index 0905de73c..3792d433f 100644
--- a/tests/unit/sortable/options.js
+++ b/tests/unit/sortable/options.js
@@ -294,17 +294,8 @@ QUnit.test( "{ forcePlaceholderSize: true } table rows", function( assert ) {
 		placeholder: "test",
 		forcePlaceholderSize: true,
 		start: function( event, ui ) {
-
-			// Support: IE 11+, Edge <79 only
-			// In IE & Edge Legacy these values may differ a little
-			// when jQuery >=3.0 <3.2 is used.
-			if ( jqMinor === "3.0." || jqMinor === "3.1." ) {
-				assert.ok( Math.abs( ui.placeholder.height() - ui.item.height() ) < 0.25,
-					"placeholder height is within 0.25 px of item's" );
-			} else {
-				assert.equal( ui.placeholder.height(), ui.item.height(),
-					"placeholder is same height as item" );
-			}
+			assert.equal( ui.placeholder.height(), ui.item.height(),
+				"placeholder is same height as item" );
 		}
 	} );
 
diff --git a/tests/unit/widget/core.js b/tests/unit/widget/core.js
index 1054bf092..fe74e18e9 100644
--- a/tests/unit/widget/core.js
+++ b/tests/unit/widget/core.js
@@ -293,9 +293,7 @@ QUnit.test( "._getCreateOptions()", function( assert ) {
 
 			assert.deepEqual( superOptions, {}, "Base implementation returns empty object" );
 
-			// Support: IE8
-			// Strict equality fails when comparing this.window in ie8
-			assert.equal( this.window[ 0 ], window, "this.window is properly defined" );
+			assert.strictEqual( this.window[ 0 ], window, "this.window is properly defined" );
 			assert.strictEqual( this.document[ 0 ], document, "this.document is properly defined" );
 
 			return {
diff --git a/themes/base/button.css b/themes/base/button.css
index f6780cb15..c432b4abc 100644
--- a/themes/base/button.css
+++ b/themes/base/button.css
@@ -18,12 +18,7 @@
 	vertical-align: middle;
 	text-align: center;
 	-webkit-user-select: none;
-	-moz-user-select: none;
-	-ms-user-select: none;
 	user-select: none;
-
-	/* Support: IE <= 11 */
-	overflow: visible;
 }
 
 .ui-button,
@@ -74,7 +69,7 @@ input.ui-button.ui-icon-notext .ui-icon {
 }
 
 /* workarounds */
-/* Support: Firefox 5 - 40 */
+/* Support: Firefox 5 - 125+ */
 input.ui-button::-moz-focus-inner,
 button.ui-button::-moz-focus-inner {
 	border: 0;
diff --git a/themes/base/controlgroup.css b/themes/base/controlgroup.css
index 24048bd79..cd9e4e520 100644
--- a/themes/base/controlgroup.css
+++ b/themes/base/controlgroup.css
@@ -54,9 +54,6 @@
 
 /* Spinner specific style fixes */
 .ui-controlgroup-vertical .ui-spinner-input {
-
-	/* Support: IE8 only, Android < 4.4 only */
-	width: 75%;
 	width: calc( 100% - 2.4em );
 }
 .ui-controlgroup-vertical .ui-spinner .ui-spinner-up {
diff --git a/themes/base/core.css b/themes/base/core.css
index 6917bb6d4..2bea103b5 100644
--- a/themes/base/core.css
+++ b/themes/base/core.css
@@ -50,7 +50,6 @@
 	left: 0;
 	position: absolute;
 	opacity: 0;
-	-ms-filter: "alpha(opacity=0)"; /* support: IE8 */
 }
 
 .ui-front {
diff --git a/themes/base/draggable.css b/themes/base/draggable.css
index c77269d93..4183f5ac4 100644
--- a/themes/base/draggable.css
+++ b/themes/base/draggable.css
@@ -7,6 +7,5 @@
  * https://jquery.org/license
  */
 .ui-draggable-handle {
-	-ms-touch-action: none;
 	touch-action: none;
 }
diff --git a/themes/base/menu.css b/themes/base/menu.css
index 83e165a5d..e35c9e8bf 100644
--- a/themes/base/menu.css
+++ b/themes/base/menu.css
@@ -21,8 +21,6 @@
 .ui-menu .ui-menu-item {
 	margin: 0;
 	cursor: pointer;
-	/* support: IE10, see #8844 */
-	list-style-image: url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
 }
 .ui-menu .ui-menu-item-wrapper {
 	position: relative;
diff --git a/themes/base/progressbar.css b/themes/base/progressbar.css
index 6c379e5bd..e1abfab46 100644
--- a/themes/base/progressbar.css
+++ b/themes/base/progressbar.css
@@ -20,7 +20,6 @@
 .ui-progressbar .ui-progressbar-overlay {
 	background: url("data:image/gif;base64,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");
 	height: 100%;
-	-ms-filter: "alpha(opacity=25)"; /* support: IE8 */
 	opacity: 0.25;
 }
 .ui-progressbar-indeterminate .ui-progressbar-value {
diff --git a/themes/base/resizable.css b/themes/base/resizable.css
index 35cd3034d..8a48c427e 100644
--- a/themes/base/resizable.css
+++ b/themes/base/resizable.css
@@ -13,7 +13,6 @@
 	position: absolute;
 	font-size: 0.1px;
 	display: block;
-	-ms-touch-action: none;
 	touch-action: none;
 }
 .ui-resizable-disabled .ui-resizable-handle,
diff --git a/themes/base/selectable.css b/themes/base/selectable.css
index 4b749755c..cb770e7cc 100644
--- a/themes/base/selectable.css
+++ b/themes/base/selectable.css
@@ -7,7 +7,6 @@
  * https://jquery.org/license
  */
 .ui-selectable {
-	-ms-touch-action: none;
 	touch-action: none;
 }
 .ui-selectable-helper {
diff --git a/themes/base/slider.css b/themes/base/slider.css
index d6d261c42..134bf14b2 100644
--- a/themes/base/slider.css
+++ b/themes/base/slider.css
@@ -18,7 +18,6 @@
 	width: 1.2em;
 	height: 1.2em;
 	cursor: pointer;
-	-ms-touch-action: none;
 	touch-action: none;
 }
 .ui-slider .ui-slider-range {
@@ -30,12 +29,6 @@
 	background-position: 0 0;
 }
 
-/* support: IE8 - See #6727 */
-.ui-slider.ui-state-disabled .ui-slider-handle,
-.ui-slider.ui-state-disabled .ui-slider-range {
-	filter: inherit;
-}
-
 .ui-slider-horizontal {
 	height: .8em;
 }
diff --git a/themes/base/sortable.css b/themes/base/sortable.css
index fe54de6ab..dc698ded8 100644
--- a/themes/base/sortable.css
+++ b/themes/base/sortable.css
@@ -7,6 +7,5 @@
  * https://jquery.org/license
  */
 .ui-sortable-handle {
-	-ms-touch-action: none;
 	touch-action: none;
 }
diff --git a/themes/base/theme.css b/themes/base/theme.css
index eb1097b82..d99a47bbc 100644
--- a/themes/base/theme.css
+++ b/themes/base/theme.css
@@ -172,19 +172,14 @@ a.ui-button:active,
 .ui-widget-content .ui-priority-secondary,
 .ui-widget-header .ui-priority-secondary {
 	opacity: .7;
-	-ms-filter: "alpha(opacity=70)"; /* support: IE8 */
 	font-weight: normal;
 }
 .ui-state-disabled,
 .ui-widget-content .ui-state-disabled,
 .ui-widget-header .ui-state-disabled {
 	opacity: .35;
-	-ms-filter: "alpha(opacity=35)"; /* support: IE8 */
 	background-image: none;
 }
-.ui-state-disabled .ui-icon {
-	-ms-filter: "alpha(opacity=35)"; /* support: IE8 - See #6059 */
-}
 
 /* Icons
 ----------------------------------*/
@@ -438,9 +433,7 @@ a.ui-button:active,
 .ui-widget-overlay {
 	background: #aaaaaa/*{bgColorOverlay}*/ /*{bgImgUrlOverlay}*/ /*{bgOverlayXPos}*/ /*{bgOverlayYPos}*/ /*{bgOverlayRepeat}*/;
 	opacity: .3/*{opacityOverlay}*/;
-	-ms-filter: "alpha(opacity=30)"/*{opacityFilterOverlay}*/; /* support: IE8 */
 }
 .ui-widget-shadow {
-	-webkit-box-shadow: 0/*{offsetLeftShadow}*/ 0/*{offsetTopShadow}*/ 5px/*{thicknessShadow}*/ #666666/*{bgColorShadow}*/;
 	box-shadow: 0/*{offsetLeftShadow}*/ 0/*{offsetTopShadow}*/ 5px/*{thicknessShadow}*/ #666666/*{bgColorShadow}*/;
 }
diff --git a/ui/core.js b/ui/core.js
index 862851391..33d7974e2 100644
--- a/ui/core.js
+++ b/ui/core.js
@@ -7,14 +7,10 @@ define( [
 	"./data",
 	"./disable-selection",
 	"./focusable",
-	"./form",
-	"./ie",
 	"./keycode",
 	"./labels",
 	"./jquery-patch",
 	"./plugin",
-	"./safe-active-element",
-	"./safe-blur",
 	"./scroll-parent",
 	"./tabbable",
 	"./unique-id",
diff --git a/ui/effect.js b/ui/effect.js
index ac9b0c809..bbbb733c3 100644
--- a/ui/effect.js
+++ b/ui/effect.js
@@ -81,26 +81,14 @@ function camelCase( string ) {
 
 function getElementStyles( elem ) {
 	var key, len,
-		style = elem.ownerDocument.defaultView ?
-			elem.ownerDocument.defaultView.getComputedStyle( elem, null ) :
-			elem.currentStyle,
+		style = elem.ownerDocument.defaultView.getComputedStyle( elem ),
 		styles = {};
 
-	if ( style && style.length && style[ 0 ] && style[ style[ 0 ] ] ) {
-		len = style.length;
-		while ( len-- ) {
-			key = style[ len ];
-			if ( typeof style[ key ] === "string" ) {
-				styles[ camelCase( key ) ] = style[ key ];
-			}
-		}
-
-	// Support: Opera, IE <9
-	} else {
-		for ( key in style ) {
-			if ( typeof style[ key ] === "string" ) {
-				styles[ key ] = style[ key ];
-			}
+	len = style.length;
+	while ( len-- ) {
+		key = style[ len ];
+		if ( typeof style[ key ] === "string" ) {
+			styles[ camelCase( key ) ] = style[ key ];
 		}
 	}
 
diff --git a/ui/focusable.js b/ui/focusable.js
index 2db058678..4920417fc 100644
--- a/ui/focusable.js
+++ b/ui/focusable.js
@@ -62,20 +62,10 @@ $.ui.focusable = function( element, hasTabindex ) {
 		focusableIfVisible = hasTabindex;
 	}
 
-	return focusableIfVisible && $( element ).is( ":visible" ) && visible( $( element ) );
+	return focusableIfVisible && $( element ).is( ":visible" ) &&
+		$( element ).css( "visibility" ) === "visible";
 };
 
-// Support: IE 8 only
-// IE 8 doesn't resolve inherit to visible/hidden for computed values
-function visible( element ) {
-	var visibility = element.css( "visibility" );
-	while ( visibility === "inherit" ) {
-		element = element.parent();
-		visibility = element.css( "visibility" );
-	}
-	return visibility === "visible";
-}
-
 $.extend( $.expr.pseudos, {
 	focusable: function( element ) {
 		return $.ui.focusable( element, $.attr( element, "tabindex" ) != null );
diff --git a/ui/form-reset-mixin.js b/ui/form-reset-mixin.js
index a60299d13..9a2e73aac 100644
--- a/ui/form-reset-mixin.js
+++ b/ui/form-reset-mixin.js
@@ -20,7 +20,6 @@
 		// AMD. Register as an anonymous module.
 		define( [
 			"jquery",
-			"./form",
 			"./version"
 		], factory );
 	} else {
@@ -45,7 +44,7 @@ return $.ui.formResetMixin = {
 	},
 
 	_bindFormResetHandler: function() {
-		this.form = this.element._form();
+		this.form = $( this.element.prop( "form" ) );
 		if ( !this.form.length ) {
 			return;
 		}
diff --git a/ui/form.js b/ui/form.js
deleted file mode 100644
index 60b052277..000000000
--- a/ui/form.js
+++ /dev/null
@@ -1,23 +0,0 @@
-( function( factory ) {
-	"use strict";
-
-	if ( typeof define === "function" && define.amd ) {
-
-		// AMD. Register as an anonymous module.
-		define( [ "jquery", "./version" ], factory );
-	} else {
-
-		// Browser globals
-		factory( jQuery );
-	}
-} )( function( $ ) {
-"use strict";
-
-// Support: IE8 Only
-// IE8 does not support the form attribute and when it is supplied. It overwrites the form prop
-// with a string, so we need to find the proper form.
-return $.fn._form = function() {
-	return typeof this[ 0 ].form === "string" ? this.closest( "form" ) : $( this[ 0 ].form );
-};
-
-} );
diff --git a/ui/ie.js b/ui/ie.js
deleted file mode 100644
index 1754b94a9..000000000
--- a/ui/ie.js
+++ /dev/null
@@ -1,18 +0,0 @@
-( function( factory ) {
-	"use strict";
-
-	if ( typeof define === "function" && define.amd ) {
-
-		// AMD. Register as an anonymous module.
-		define( [ "jquery", "./version" ], factory );
-	} else {
-
-		// Browser globals
-		factory( jQuery );
-	}
-} )( function( $ ) {
-"use strict";
-
-// This file is deprecated
-return $.ui.ie = !!/msie [\w.]+/.exec( navigator.userAgent.toLowerCase() );
-} );
diff --git a/ui/labels.js b/ui/labels.js
index 9f1c3296b..4f6533451 100644
--- a/ui/labels.js
+++ b/ui/labels.js
@@ -39,9 +39,8 @@ return $.fn.labels = function() {
 		return this.pushStack( this[ 0 ].labels );
 	}
 
-	// Support: IE <= 11, FF <= 37, Android <= 2.3 only
-	// Above browsers do not support control.labels. Everything below is to support them
-	// as well as document fragments. control.labels does not work on document fragments
+	// If `control.labels` is empty - e.g. inside of document fragments - find
+	// the labels manually
 	labels = this.eq( 0 ).parents( "label" );
 
 	// Look for the label based on the id
diff --git a/ui/safe-active-element.js b/ui/safe-active-element.js
deleted file mode 100644
index 9d6968e08..000000000
--- a/ui/safe-active-element.js
+++ /dev/null
@@ -1,44 +0,0 @@
-( function( factory ) {
-	"use strict";
-
-	if ( typeof define === "function" && define.amd ) {
-
-		// AMD. Register as an anonymous module.
-		define( [ "jquery", "./version" ], factory );
-	} else {
-
-		// Browser globals
-		factory( jQuery );
-	}
-} )( function( $ ) {
-"use strict";
-
-return $.ui.safeActiveElement = function( document ) {
-	var activeElement;
-
-	// Support: IE 9 only
-	// IE9 throws an "Unspecified error" accessing document.activeElement from an <iframe>
-	try {
-		activeElement = document.activeElement;
-	} catch ( error ) {
-		activeElement = document.body;
-	}
-
-	// Support: IE 9 - 11 only
-	// IE may return null instead of an element
-	// Interestingly, this only seems to occur when NOT in an iframe
-	if ( !activeElement ) {
-		activeElement = document.body;
-	}
-
-	// Support: IE 11 only
-	// IE11 returns a seemingly empty object in some cases when accessing
-	// document.activeElement from an <iframe>
-	if ( !activeElement.nodeName ) {
-		activeElement = document.body;
-	}
-
-	return activeElement;
-};
-
-} );
diff --git a/ui/safe-blur.js b/ui/safe-blur.js
deleted file mode 100644
index c0b3b8a1e..000000000
--- a/ui/safe-blur.js
+++ /dev/null
@@ -1,25 +0,0 @@
-( function( factory ) {
-	"use strict";
-
-	if ( typeof define === "function" && define.amd ) {
-
-		// AMD. Register as an anonymous module.
-		define( [ "jquery", "./version" ], factory );
-	} else {
-
-		// Browser globals
-		factory( jQuery );
-	}
-} )( function( $ ) {
-"use strict";
-
-return $.ui.safeBlur = function( element ) {
-
-	// Support: IE9 - 10 only
-	// If the <body> is blurred, IE will switch windows, see #9420
-	if ( element && element.nodeName.toLowerCase() !== "body" ) {
-		$( element ).trigger( "blur" );
-	}
-};
-
-} );
diff --git a/ui/widgets/accordion.js b/ui/widgets/accordion.js
index d5d71224d..b6a7a7eee 100644
--- a/ui/widgets/accordion.js
+++ b/ui/widgets/accordion.js
@@ -187,13 +187,7 @@ return $.widget( "ui.accordion", {
 		this._super( value );
 
 		this.element.attr( "aria-disabled", value );
-
-		// Support: IE8 Only
-		// #5332 / #6059 - opacity doesn't cascade to positioned elements in IE
-		// so we need to add the disabled class to the headers and panels
 		this._toggleClass( null, "ui-state-disabled", !!value );
-		this._toggleClass( this.headers.add( this.headers.next() ), null, "ui-state-disabled",
-			!!value );
 	},
 
 	_keydown: function( event ) {
@@ -611,10 +605,6 @@ return $.widget( "ui.accordion", {
 		this._removeClass( prev, "ui-accordion-header-active" )
 			._addClass( prev, "ui-accordion-header-collapsed" );
 
-		// Work around for rendering bug in IE (#5421)
-		if ( toHide.length ) {
-			toHide.parent()[ 0 ].className = toHide.parent()[ 0 ].className;
-		}
 		this._trigger( "activate", null, data );
 	}
 } );
diff --git a/ui/widgets/autocomplete.js b/ui/widgets/autocomplete.js
index ac2cfe42b..57e59820c 100644
--- a/ui/widgets/autocomplete.js
+++ b/ui/widgets/autocomplete.js
@@ -27,7 +27,6 @@
 			"./menu",
 			"../keycode",
 			"../position",
-			"../safe-active-element",
 			"../version",
 			"../widget"
 		], factory );
@@ -84,9 +83,9 @@ $.widget( "ui.autocomplete", {
 
 		// Textareas are always multi-line
 		// Inputs are always single-line, even if inside a contentEditable element
-		// IE also treats inputs as contentEditable
-		// All other element types are determined by whether or not they're contentEditable
-		this.isMultiLine = isTextarea || !isInput && this._isContentEditable( this.element );
+		// All other element types are determined by whether they're contentEditable
+		this.isMultiLine = isTextarea ||
+			!isInput && this.element.prop( "contentEditable" ) === "true";
 
 		this.valueMethod = this.element[ isTextarea || isInput ? "val" : "text" ];
 		this.isNewMenu = true;
@@ -150,7 +149,6 @@ $.widget( "ui.autocomplete", {
 
 						// Different browsers have different default behavior for escape
 						// Single press can mean undo or clear
-						// Double press in IE means clear the whole form
 						event.preventDefault();
 					}
 					break;
@@ -219,16 +217,6 @@ $.widget( "ui.autocomplete", {
 				role: null
 			} )
 			.hide()
-
-			// Support: IE 11 only, Edge <= 14
-			// For other browsers, we preventDefault() on the mousedown event
-			// to keep the dropdown from taking focus from the input. This doesn't
-			// work for IE/Edge, causing problems with selection and scrolling (#9638)
-			// Happily, IE and Edge support an "unselectable" attribute that
-			// prevents an element from receiving focus, exactly what we want here.
-			.attr( {
-				"unselectable": "on"
-			} )
 			.menu( "instance" );
 
 		this._addClass( this.menu.element, "ui-autocomplete", "ui-front" );
@@ -241,7 +229,7 @@ $.widget( "ui.autocomplete", {
 			menufocus: function( event, ui ) {
 				var label, item;
 
-				// support: Firefox
+				// Support: Firefox
 				// Prevent accidental activation of menu items in Firefox (#7024 #9118)
 				if ( this.isNewMenu ) {
 					this.isNewMenu = false;
@@ -279,17 +267,9 @@ $.widget( "ui.autocomplete", {
 					previous = this.previous;
 
 				// Only trigger when focus was lost (click on menu)
-				if ( this.element[ 0 ] !== $.ui.safeActiveElement( this.document[ 0 ] ) ) {
+				if ( this.element[ 0 ] !== this.document[ 0 ].activeElement ) {
 					this.element.trigger( "focus" );
 					this.previous = previous;
-
-					// #6109 - IE triggers two focus events and the second
-					// is asynchronous, so we need to reset the previous
-					// term synchronously and asynchronously :-(
-					this._delay( function() {
-						this.previous = previous;
-						this.selectedItem = item;
-					} );
 				}
 
 				if ( false !== this._trigger( "select", event, { item: item } ) ) {
@@ -608,24 +588,6 @@ $.widget( "ui.autocomplete", {
 			// Prevents moving cursor to beginning/end of the text field in some browsers
 			event.preventDefault();
 		}
-	},
-
-	// Support: Chrome <=50
-	// We should be able to just use this.element.prop( "isContentEditable" )
-	// but hidden elements always report false in Chrome.
-	// https://code.google.com/p/chromium/issues/detail?id=313082
-	_isContentEditable: function( element ) {
-		if ( !element.length ) {
-			return false;
-		}
-
-		var editable = element.prop( "contentEditable" );
-
-		if ( editable === "inherit" ) {
-			return this._isContentEditable( element.parent() );
-		}
-
-		return editable === "true";
 	}
 } );
 
diff --git a/ui/widgets/button.js b/ui/widgets/button.js
index 02708d620..08a4b61c5 100644
--- a/ui/widgets/button.js
+++ b/ui/widgets/button.js
@@ -109,9 +109,9 @@ $.widget( "ui.button", {
 					if ( event.keyCode === $.ui.keyCode.SPACE ) {
 						event.preventDefault();
 
-						// Support: PhantomJS <= 1.9, IE 8 Only
-						// If a native click is available use it so we actually cause navigation
-						// otherwise just trigger a click event
+						// If a native click is available use it, so we
+						// actually cause navigation. Otherwise, just trigger
+						// a click event.
 						if ( this.element[ 0 ].click ) {
 							this.element[ 0 ].click();
 						} else {
diff --git a/ui/widgets/checkboxradio.js b/ui/widgets/checkboxradio.js
index add80d80a..fc812116e 100644
--- a/ui/widgets/checkboxradio.js
+++ b/ui/widgets/checkboxradio.js
@@ -168,7 +168,7 @@ $.widget( "ui.checkboxradio", [ $.ui.formResetMixin, {
 
 			// Not inside a form, check all inputs that also are not inside a form
 			group = $( nameSelector ).filter( function() {
-				return $( this )._form().length === 0;
+				return $( $( this ).prop( "form" ) ).length === 0;
 			} );
 		}
 
diff --git a/ui/widgets/dialog.js b/ui/widgets/dialog.js
index cbda81636..4ba9d1117 100644
--- a/ui/widgets/dialog.js
+++ b/ui/widgets/dialog.js
@@ -31,8 +31,6 @@
 			"../focusable",
 			"../keycode",
 			"../position",
-			"../safe-active-element",
-			"../safe-blur",
 			"../tabbable",
 			"../unique-id",
 			"../version",
@@ -229,7 +227,7 @@ $.widget( "ui.dialog", {
 			// Hiding a focused element doesn't trigger blur in WebKit
 			// so in case we have nothing to focus on, explicitly blur the active element
 			// https://bugs.webkit.org/show_bug.cgi?id=47182
-			$.ui.safeBlur( $.ui.safeActiveElement( this.document[ 0 ] ) );
+			$( this.document[ 0 ].activeElement ).trigger( "blur" );
 		}
 
 		this._hide( this.uiDialog, this.options.hide, function() {
@@ -273,7 +271,7 @@ $.widget( "ui.dialog", {
 		}
 
 		this._isOpen = true;
-		this.opener = $( $.ui.safeActiveElement( this.document[ 0 ] ) );
+		this.opener = $( this.document[ 0 ].activeElement );
 
 		this._size();
 		this._position();
@@ -329,7 +327,7 @@ $.widget( "ui.dialog", {
 	},
 
 	_restoreTabbableFocus: function() {
-		var activeElement = $.ui.safeActiveElement( this.document[ 0 ] ),
+		var activeElement = this.document[ 0 ].activeElement,
 			isActive = this.uiDialog[ 0 ] === activeElement ||
 				$.contains( this.uiDialog[ 0 ], activeElement );
 		if ( !isActive ) {
@@ -340,11 +338,6 @@ $.widget( "ui.dialog", {
 	_keepFocus: function( event ) {
 		event.preventDefault();
 		this._restoreTabbableFocus();
-
-		// support: IE
-		// IE <= 8 doesn't prevent moving focus even with event.preventDefault()
-		// so we check again later
-		this._delay( this._restoreTabbableFocus );
 	},
 
 	_createWrapper: function() {
@@ -427,9 +420,6 @@ $.widget( "ui.dialog", {
 			}
 		} );
 
-		// Support: IE
-		// Use type="button" to prevent enter keypresses in textboxes from closing the
-		// dialog in IE (#9312)
 		this.uiDialogTitlebarClose = $( "<button type='button'></button>" )
 			.button( {
 				label: $( "<a>" ).text( this.options.closeText ).html(),
diff --git a/ui/widgets/draggable.js b/ui/widgets/draggable.js
index 91443fac5..e0abdd26f 100644
--- a/ui/widgets/draggable.js
+++ b/ui/widgets/draggable.js
@@ -25,8 +25,6 @@
 			"./mouse",
 			"../data",
 			"../plugin",
-			"../safe-active-element",
-			"../safe-blur",
 			"../scroll-parent",
 			"../version",
 			"../widget"
@@ -147,7 +145,7 @@ $.widget( "ui.draggable", $.ui.mouse, {
 	},
 
 	_blurActiveElement: function( event ) {
-		var activeElement = $.ui.safeActiveElement( this.document[ 0 ] ),
+		var activeElement = this.document[ 0 ].activeElement,
 			target = $( event.target );
 
 		// Don't blur if the event occurred on an element that is within
@@ -158,7 +156,7 @@ $.widget( "ui.draggable", $.ui.mouse, {
 		}
 
 		// Blur any element that currently has focus, see #4261
-		$.ui.safeBlur( activeElement );
+		$( activeElement ).trigger( "blur" );
 	},
 
 	_mouseStart: function( event ) {
diff --git a/ui/widgets/menu.js b/ui/widgets/menu.js
index 1ef4b8a3d..f3fdc82c8 100644
--- a/ui/widgets/menu.js
+++ b/ui/widgets/menu.js
@@ -26,7 +26,6 @@
 			"jquery",
 			"../keycode",
 			"../position",
-			"../safe-active-element",
 			"../unique-id",
 			"../version",
 			"../widget"
@@ -87,7 +86,7 @@ return $.widget( "ui.menu", {
 			},
 			"click .ui-menu-item": function( event ) {
 				var target = $( event.target );
-				var active = $( $.ui.safeActiveElement( this.document[ 0 ] ) );
+				var active = $( this.document[ 0 ].activeElement );
 				if ( !this.mouseHandled && target.not( ".ui-state-disabled" ).length ) {
 					this.select( event );
 
@@ -131,7 +130,7 @@ return $.widget( "ui.menu", {
 				this._delay( function() {
 					var notContained = !$.contains(
 						this.element[ 0 ],
-						$.ui.safeActiveElement( this.document[ 0 ] )
+						this.document[ 0 ].activeElement
 					);
 					if ( notContained ) {
 						this.collapseAll( event );
diff --git a/ui/widgets/mouse.js b/ui/widgets/mouse.js
index 1dcac5277..ef9dd8dbe 100644
--- a/ui/widgets/mouse.js
+++ b/ui/widgets/mouse.js
@@ -20,7 +20,6 @@
 		// AMD. Register as an anonymous module.
 		define( [
 			"jquery",
-			"../ie",
 			"../version",
 			"../widget"
 		], factory );
@@ -90,12 +89,10 @@ return $.widget( "ui.mouse", {
 		this._mouseDownEvent = event;
 
 		var that = this,
-			btnIsLeft = ( event.which === 1 ),
-
-			// event.target.nodeName works around a bug in IE 8 with
-			// disabled inputs (#7620)
-			elIsCancel = ( typeof this.options.cancel === "string" && event.target.nodeName ?
-				$( event.target ).closest( this.options.cancel ).length : false );
+			btnIsLeft = event.which === 1,
+			elIsCancel = typeof this.options.cancel === "string" ?
+				$( event.target ).closest( this.options.cancel ).length :
+				false;
 		if ( !btnIsLeft || elIsCancel || !this._mouseCapture( event ) ) {
 			return true;
 		}
@@ -141,28 +138,17 @@ return $.widget( "ui.mouse", {
 	_mouseMove: function( event ) {
 
 		// Only check for mouseups outside the document if you've moved inside the document
-		// at least once. This prevents the firing of mouseup in the case of IE<9, which will
-		// fire a mousemove event if content is placed under the cursor. See #7778
-		// Support: IE <9
-		if ( this._mouseMoved ) {
+		// at least once.
+		if ( this._mouseMoved && !event.which ) {
 
-			// IE mouseup check - mouseup happened when mouse was out of window
-			if ( $.ui.ie && ( !document.documentMode || document.documentMode < 9 ) &&
-					!event.button ) {
+			// Support: Safari <=8 - 9
+			// Safari sets which to 0 if you press any of the following keys
+			// during a drag (#14461)
+			if ( event.originalEvent.altKey || event.originalEvent.ctrlKey ||
+					event.originalEvent.metaKey || event.originalEvent.shiftKey ) {
+				this.ignoreMissingWhich = true;
+			} else if ( !this.ignoreMissingWhich ) {
 				return this._mouseUp( event );
-
-			// Iframe mouseup check - mouseup occurred in another document
-			} else if ( !event.which ) {
-
-				// Support: Safari <=8 - 9
-				// Safari sets which to 0 if you press any of the following keys
-				// during a drag (#14461)
-				if ( event.originalEvent.altKey || event.originalEvent.ctrlKey ||
-						event.originalEvent.metaKey || event.originalEvent.shiftKey ) {
-					this.ignoreMissingWhich = true;
-				} else if ( !this.ignoreMissingWhich ) {
-					return this._mouseUp( event );
-				}
 			}
 		}
 
diff --git a/ui/widgets/resizable.js b/ui/widgets/resizable.js
index e163b03fe..1698d55e8 100644
--- a/ui/widgets/resizable.js
+++ b/ui/widgets/resizable.js
@@ -149,9 +149,8 @@ $.widget( "ui.resizable", $.ui.mouse, {
 			};
 
 			this.element.css( margins );
-			this.originalElement.css( "margin", 0 );
 
-			// support: Safari
+			// Support: Safari
 			// Prevent Safari textarea resize
 			this.originalResizeStyle = this.originalElement.css( "resize" );
 			this.originalElement.css( "resize", "none" );
@@ -162,10 +161,6 @@ $.widget( "ui.resizable", $.ui.mouse, {
 				display: "block"
 			} ) );
 
-			// Support: IE9
-			// avoid IE jump (hard set the margin)
-			this.originalElement.css( margins );
-
 			this._proportionallyResize();
 		}
 
diff --git a/ui/widgets/selectmenu.js b/ui/widgets/selectmenu.js
index b1e2033ba..eecd368f5 100644
--- a/ui/widgets/selectmenu.js
+++ b/ui/widgets/selectmenu.js
@@ -167,12 +167,6 @@ return $.widget( "ui.selectmenu", [ $.ui.formResetMixin, {
 				role: "listbox",
 				select: function( event, ui ) {
 					event.preventDefault();
-
-					// Support: IE8
-					// If the item was selected via a click, the text selection
-					// will be destroyed in IE
-					that._setSelection();
-
 					that._select( ui.item.data( "ui-selectmenu-item" ), event );
 				},
 				focus: function( event, ui ) {
@@ -409,20 +403,9 @@ return $.widget( "ui.selectmenu", [ $.ui.formResetMixin, {
 			return;
 		}
 
-		if ( window.getSelection ) {
-			selection = window.getSelection();
-			selection.removeAllRanges();
-			selection.addRange( this.range );
-
-		// Support: IE8
-		} else {
-			this.range.select();
-		}
-
-		// Support: IE
-		// Setting the text selection kills the button focus in IE, but
-		// restoring the focus doesn't kill the selection.
-		this.button.trigger( "focus" );
+		selection = window.getSelection();
+		selection.removeAllRanges();
+		selection.addRange( this.range );
 	},
 
 	_documentClick: {
@@ -442,17 +425,9 @@ return $.widget( "ui.selectmenu", [ $.ui.formResetMixin, {
 
 		// Prevent text selection from being reset when interacting with the selectmenu (#10144)
 		mousedown: function() {
-			var selection;
-
-			if ( window.getSelection ) {
-				selection = window.getSelection();
-				if ( selection.rangeCount ) {
-					this.range = selection.getRangeAt( 0 );
-				}
-
-			// Support: IE8
-			} else {
-				this.range = document.selection.createRange();
+			var selection = window.getSelection();
+			if ( selection.rangeCount ) {
+				this.range = selection.getRangeAt( 0 );
 			}
 		},
 
@@ -643,11 +618,7 @@ return $.widget( "ui.selectmenu", [ $.ui.formResetMixin, {
 	_resizeMenu: function() {
 		this.menu.outerWidth( Math.max(
 			this.button.outerWidth(),
-
-			// Support: IE10
-			// IE10 wraps long text (possibly a rounding bug)
-			// so we add 1px to avoid the wrapping
-			this.menu.width( "" ).outerWidth() + 1
+			this.menu.width( "" ).outerWidth()
 		) );
 	},
 
diff --git a/ui/widgets/sortable.js b/ui/widgets/sortable.js
index 70dc7e703..32333b6f5 100644
--- a/ui/widgets/sortable.js
+++ b/ui/widgets/sortable.js
@@ -24,7 +24,6 @@
 			"jquery",
 			"./mouse",
 			"../data",
-			"../ie",
 			"../scroll-parent",
 			"../version",
 			"../widget"
@@ -276,10 +275,6 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 		if ( o.cursor && o.cursor !== "auto" ) { // cursor option
 			body = this.document.find( "body" );
 
-			// Support: IE
-			this.storedCursor = body.css( "cursor" );
-			body.css( "cursor", o.cursor );
-
 			this.storedStylesheet =
 				$( "<style>*{ cursor: " + o.cursor + " !important; }</style>" ).appendTo( body );
 		}
@@ -1197,11 +1192,9 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 			po.top += this.scrollParent.scrollTop();
 		}
 
-		// This needs to be actually done for all browsers, since pageX/pageY includes this
-		// information with an ugly IE fix
-		if ( this.offsetParent[ 0 ] === this.document[ 0 ].body ||
-				( this.offsetParent[ 0 ].tagName &&
-				this.offsetParent[ 0 ].tagName.toLowerCase() === "html" && $.ui.ie ) ) {
+		// This needs to be actually done for all browsers, since pageX/pageY includes
+		// this information.
+		if ( this.offsetParent[ 0 ] === this.document[ 0 ].body ) {
 			po = { top: 0, left: 0 };
 		}
 
@@ -1549,8 +1542,7 @@ return $.widget( "ui.sortable", $.ui.mouse, {
 		}
 
 		//Do what was originally in plugins
-		if ( this.storedCursor ) {
-			this.document.find( "body" ).css( "cursor", this.storedCursor );
+		if ( this.storedStylesheet ) {
 			this.storedStylesheet.remove();
 		}
 		if ( this._storedOpacity ) {
diff --git a/ui/widgets/spinner.js b/ui/widgets/spinner.js
index b92b8ab52..d999d85d7 100644
--- a/ui/widgets/spinner.js
+++ b/ui/widgets/spinner.js
@@ -27,7 +27,6 @@
 			"./button",
 			"../version",
 			"../keycode",
-			"../safe-active-element",
 			"../widget"
 		], factory );
 	} else {
@@ -131,11 +130,6 @@ $.widget( "ui.spinner", {
 			this.previous = this.element.val();
 		},
 		blur: function( event ) {
-			if ( this.cancelBlur ) {
-				delete this.cancelBlur;
-				return;
-			}
-
 			this._stop();
 			this._refresh();
 			if ( this.previous !== this.element.val() ) {
@@ -143,7 +137,7 @@ $.widget( "ui.spinner", {
 			}
 		},
 		mousewheel: function( event, delta ) {
-			var activeElement = $.ui.safeActiveElement( this.document[ 0 ] );
+			var activeElement = this.document[ 0 ].activeElement;
 			var isActive = this.element[ 0 ] === activeElement;
 
 			if ( !isActive || !delta ) {
@@ -171,20 +165,13 @@ $.widget( "ui.spinner", {
 			// If the input is focused then this.previous is properly set from
 			// when the input first received focus. If the input is not focused
 			// then we need to set this.previous based on the value before spinning.
-			previous = this.element[ 0 ] === $.ui.safeActiveElement( this.document[ 0 ] ) ?
+			previous = this.element[ 0 ] === this.document[ 0 ].activeElement ?
 				this.previous : this.element.val();
 			function checkFocus() {
-				var isActive = this.element[ 0 ] === $.ui.safeActiveElement( this.document[ 0 ] );
+				var isActive = this.element[ 0 ] === this.document[ 0 ].activeElement;
 				if ( !isActive ) {
 					this.element.trigger( "focus" );
 					this.previous = previous;
-
-					// support: IE
-					// IE sets focus asynchronously, so we need to check if focus
-					// moved off of the input because the user clicked on the button.
-					this._delay( function() {
-						this.previous = previous;
-					} );
 				}
 			}
 
@@ -192,16 +179,6 @@ $.widget( "ui.spinner", {
 			event.preventDefault();
 			checkFocus.call( this );
 
-			// Support: IE
-			// IE doesn't prevent moving focus even with event.preventDefault()
-			// so we set a flag to know when we should ignore the blur event
-			// and check (again) if focus moved off of the input.
-			this.cancelBlur = true;
-			this._delay( function() {
-				delete this.cancelBlur;
-				checkFocus.call( this );
-			} );
-
 			if ( this._start( event ) === false ) {
 				return;
 			}
diff --git a/ui/widgets/tabs.js b/ui/widgets/tabs.js
index 465b48cec..e191dfbb4 100644
--- a/ui/widgets/tabs.js
+++ b/ui/widgets/tabs.js
@@ -25,7 +25,6 @@
 		define( [
 			"jquery",
 			"../keycode",
-			"../safe-active-element",
 			"../unique-id",
 			"../version",
 			"../widget"
@@ -171,7 +170,7 @@ $.widget( "ui.tabs", {
 	},
 
 	_tabKeydown: function( event ) {
-		var focusedTab = $( $.ui.safeActiveElement( this.document[ 0 ] ) ).closest( "li" ),
+		var focusedTab = $( this.document[ 0 ].activeElement ).closest( "li" ),
 			selectedIndex = this.tabs.index( focusedTab ),
 			goingForward = true;
 
@@ -408,18 +407,6 @@ $.widget( "ui.tabs", {
 				if ( $( this ).is( ".ui-state-disabled" ) ) {
 					event.preventDefault();
 				}
-			} )
-
-			// Support: IE <9
-			// Preventing the default action in mousedown doesn't prevent IE
-			// from focusing the element, so if the anchor gets focused, blur.
-			// We don't have to worry about focusing the previously focused
-			// element since clicking on a non-focusable element should focus
-			// the body anyway.
-			.on( "focus" + this.eventNamespace, ".ui-tabs-anchor", function() {
-				if ( $( this ).closest( "li" ).is( ".ui-state-disabled" ) ) {
-					this.blur();
-				}
 			} );
 
 		this.tabs = this.tablist.find( "> li:has(a[href])" )
@@ -877,10 +864,7 @@ $.widget( "ui.tabs", {
 	_ajaxSettings: function( anchor, event, eventData ) {
 		var that = this;
 		return {
-
-			// Support: IE <11 only
-			// Strip any hash that exists to prevent errors with the Ajax request
-			url: anchor.attr( "href" ).replace( /#.*$/, "" ),
+			url: anchor.attr( "href" ),
 			beforeSend: function( jqXHR, settings ) {
 				return that._trigger( "beforeLoad", event,
 					$.extend( { jqXHR: jqXHR, ajaxSettings: settings }, eventData ) );
diff --git a/ui/widgets/tooltip.js b/ui/widgets/tooltip.js
index b626c5d10..d23da1922 100644
--- a/ui/widgets/tooltip.js
+++ b/ui/widgets/tooltip.js
@@ -227,25 +227,20 @@ $.widget( "ui.tooltip", {
 
 		content = contentOption.call( target[ 0 ], function( response ) {
 
-			// IE may instantly serve a cached response for ajax requests
-			// delay this call to _open so the other call to _open runs first
-			that._delay( function() {
+			// Ignore async response if tooltip was closed already
+			if ( !target.data( "ui-tooltip-open" ) ) {
+				return;
+			}
 
-				// Ignore async response if tooltip was closed already
-				if ( !target.data( "ui-tooltip-open" ) ) {
-					return;
-				}
-
-				// JQuery creates a special event for focusin when it doesn't
-				// exist natively. To improve performance, the native event
-				// object is reused and the type is changed. Therefore, we can't
-				// rely on the type being correct after the event finished
-				// bubbling, so we set it back to the previous value. (#8740)
-				if ( event ) {
-					event.type = eventType;
-				}
-				this._open( event, target, response );
-			} );
+			// JQuery creates a special event for focusin when it doesn't
+			// exist natively. To improve performance, the native event
+			// object is reused and the type is changed. Therefore, we can't
+			// rely on the type being correct after the event finished
+			// bubbling, so we set it back to the previous value. (#8740)
+			if ( event ) {
+				event.type = eventType;
+			}
+			that._open( event, target, response );
 		} );
 		if ( content ) {
 			this._open( event, target, content );