diff --git a/includes/Html/Html.php b/includes/Html/Html.php
index e57b1ad60b5..9f5543be91f 100644
--- a/includes/Html/Html.php
+++ b/includes/Html/Html.php
@@ -26,7 +26,6 @@
 namespace MediaWiki\Html;
 
 use FormatJson;
-use InvalidArgumentException;
 use MediaWiki\MainConfigNames;
 use MediaWiki\MediaWikiServices;
 use MediaWiki\Request\ContentSecurityPolicy;
@@ -109,75 +108,29 @@ class Html {
 	];
 
 	/**
-	 * Modifies a set of attributes meant for button elements
-	 * and apply a set of default attributes when $wgUseMediaWikiUIEverywhere enabled.
+	 * Modifies a set of attributes meant for button elements.
+	 *
 	 * @param array $attrs HTML attributes in an associative array
 	 * @param string[] $modifiers classes to add to the button
 	 * @see https://tools.wmflabs.org/styleguide/desktop/index.html for guidance on available modifiers
 	 * @return array Modified attributes array
 	 */
 	public static function buttonAttributes( array $attrs, array $modifiers = [] ) {
-		$useMediaWikiUIEverywhere =
-			MediaWikiServices::getInstance()->getMainConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere );
-		if ( $useMediaWikiUIEverywhere ) {
-			if ( isset( $attrs['class'] ) ) {
-				if ( is_array( $attrs['class'] ) ) {
-					$attrs['class'][] = 'mw-ui-button';
-					$attrs['class'] = array_merge( $attrs['class'], $modifiers );
-					// ensure compatibility with Xml
-					$attrs['class'] = implode( ' ', $attrs['class'] );
-				} else {
-					$attrs['class'] .= ' mw-ui-button ' . implode( ' ', $modifiers );
-				}
-			} else {
-				// ensure compatibility with Xml
-				$attrs['class'] = 'mw-ui-button ' . implode( ' ', $modifiers );
-			}
-		}
 		return $attrs;
 	}
 
 	/**
-	 * Modifies a set of attributes meant for text input elements
-	 * and apply a set of default attributes.
+	 * Modifies a set of attributes meant for text input elements.
 	 *
 	 * @param array $attrs An attribute array.
 	 * @return array Modified attributes array
 	 */
 	public static function getTextInputAttributes( array $attrs ) {
-		$useMediaWikiUIEverywhere = MediaWikiServices::getInstance()
-			->getMainConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere );
-		if ( $useMediaWikiUIEverywhere ) {
-			$cdxInputClass = 'cdx-text-input__input';
-			// This will only apply if the input is not using official Codex classes.
-			// In future this should trigger a deprecation warning.
-			if ( isset( $attrs['class'] ) ) { // see expandAttributes() for supported attr formats
-				if ( is_array( $attrs['class'] ) ) {
-					if (
-						!in_array( $cdxInputClass, $attrs['class'], true ) &&
-						!( $attrs['class'][$cdxInputClass] ?? false )
-					) {
-						$attrs['class']['mw-ui-input'] = true;
-					}
-				} elseif ( is_string( $attrs['class'] ) ) {
-					if ( !preg_match( "/(^| )$cdxInputClass($| )/", $attrs['class'] ) ) {
-						$attrs['class'] .= ' mw-ui-input';
-					}
-				} else {
-					throw new InvalidArgumentException(
-						'Unexpected class attr of type ' . gettype( $attrs['class'] )
-					);
-				}
-			} else {
-				$attrs['class'] = 'mw-ui-input';
-			}
-		}
 		return $attrs;
 	}
 
 	/**
-	 * Returns an HTML link element in a string styled as a button
-	 * (when $wgUseMediaWikiUIEverywhere is enabled).
+	 * Returns an HTML link element in a string.
 	 *
 	 * @param string $text The text of the element. Will be escaped (not raw HTML)
 	 * @param array $attrs Associative array of attributes, e.g., [
@@ -196,8 +149,7 @@ class Html {
 	}
 
 	/**
-	 * Returns an HTML link element in a string styled as a button
-	 * (when $wgUseMediaWikiUIEverywhere is enabled).
+	 * Returns an HTML link element in a string styled as a button.
 	 *
 	 * @param string $contents The raw HTML contents of the element: *not*
 	 *   escaped!
diff --git a/includes/actions/McrUndoAction.php b/includes/actions/McrUndoAction.php
index b36212ffa4f..84a2a3c490c 100644
--- a/includes/actions/McrUndoAction.php
+++ b/includes/actions/McrUndoAction.php
@@ -101,12 +101,6 @@ class McrUndoAction extends FormAction {
 
 		$out = $this->getOutput();
 		$out->setRobotPolicy( 'noindex,nofollow' );
-		if ( $this->getContext()->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere ) ) {
-			$out->addModuleStyles( [
-				'mediawiki.ui.input',
-				'mediawiki.ui.checkbox',
-			] );
-		}
 
 		// IP warning headers copied from EditPage
 		// (should more be copied?)
diff --git a/includes/htmlform/HTMLForm.php b/includes/htmlform/HTMLForm.php
index dbcfe41aea0..1c8145958e1 100644
--- a/includes/htmlform/HTMLForm.php
+++ b/includes/htmlform/HTMLForm.php
@@ -1415,8 +1415,6 @@ class HTMLForm extends ContextSource {
 	 */
 	public function getButtons() {
 		$buttons = '';
-		$useMediaWikiUIEverywhere =
-			$this->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere );
 
 		if ( $this->mShowSubmit ) {
 			$attribs = [];
@@ -1435,13 +1433,6 @@ class HTMLForm extends ContextSource {
 
 			$attribs['class'] = [ 'mw-htmlform-submit' ];
 
-			if ( $useMediaWikiUIEverywhere ) {
-				foreach ( $this->mSubmitFlags as $flag ) {
-					$attribs['class'][] = 'mw-ui-' . $flag;
-				}
-				$attribs['class'][] = 'mw-ui-button';
-			}
-
 			$buttons .= Xml::submitButton( $this->getSubmitText(), $attribs ) . "\n";
 		}
 
@@ -1451,7 +1442,6 @@ class HTMLForm extends ContextSource {
 				[
 					'type' => 'reset',
 					'value' => $this->msg( 'htmlform-reset' )->text(),
-					'class' => $useMediaWikiUIEverywhere ? 'mw-ui-button' : null,
 				]
 			) . "\n";
 		}
@@ -1461,7 +1451,6 @@ class HTMLForm extends ContextSource {
 			$buttons .= Html::element(
 					'a',
 					[
-						'class' => $useMediaWikiUIEverywhere ? 'mw-ui-button' : null,
 						'href' => $target,
 					],
 					$this->msg( 'cancel' )->text()
@@ -1495,11 +1484,6 @@ class HTMLForm extends ContextSource {
 				$attrs['id'] = $button['id'];
 			}
 
-			if ( $useMediaWikiUIEverywhere ) {
-				$attrs['class'] = (array)( $attrs['class'] ?? [] );
-				$attrs['class'][] = 'mw-ui-button';
-			}
-
 			$buttons .= Html::rawElement( 'button', $attrs, $label ) . "\n";
 		}
 
diff --git a/includes/htmlform/VFormHTMLForm.php b/includes/htmlform/VFormHTMLForm.php
index 7597725653b..10a71f8195e 100644
--- a/includes/htmlform/VFormHTMLForm.php
+++ b/includes/htmlform/VFormHTMLForm.php
@@ -46,10 +46,6 @@ class VFormHTMLForm extends HTMLForm {
 	}
 
 	public function getHTML( $submitResult ) {
-		// This is required for VForm HTMLForms that use that style regardless
-		// of wgUseMediaWikiUIEverywhere (since they pre-date it).
-		// When wgUseMediaWikiUIEverywhere is removed, this should be consolidated
-		// with the addModuleStyles in SpecialPage->setHeaders.
 		$this->getOutput()->addModuleStyles( [
 			'mediawiki.ui',
 			'mediawiki.ui.button',
diff --git a/includes/htmlform/fields/HTMLButtonField.php b/includes/htmlform/fields/HTMLButtonField.php
index 36c156ee66c..08f23c3f94b 100644
--- a/includes/htmlform/fields/HTMLButtonField.php
+++ b/includes/htmlform/fields/HTMLButtonField.php
@@ -1,7 +1,6 @@
 <?php
 
 use MediaWiki\Html\Html;
-use MediaWiki\MainConfigNames;
 
 /**
  * Adds a generic button inline to the form. Does not do anything, you must add
@@ -69,15 +68,11 @@ class HTMLButtonField extends HTMLFormField {
 	public function getInputHTML( $value ) {
 		$flags = '';
 		$prefix = 'mw-htmlform-';
-		$isCodexForm = $this->mParent instanceof CodexHTMLForm;
-		if ( $this->mParent instanceof VFormHTMLForm ||
-			( !$isCodexForm && $this->mParent->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere ) )
-		) {
+		if ( $this->mParent instanceof VFormHTMLForm ) {
 			$prefix = 'mw-ui-';
 			// add mw-ui-button separately, so the descriptor doesn't need to set it
 			$flags .= ' ' . $prefix . 'button';
-		}
-		if ( $isCodexForm ) {
+		} elseif ( $this->mParent instanceof CodexHTMLForm ) {
 			$flags .= ' cdx-button cdx-button--action-progressive cdx-button--weight-primary';
 		}
 		foreach ( $this->mFlags as $flag ) {
diff --git a/includes/htmlform/fields/HTMLCheckField.php b/includes/htmlform/fields/HTMLCheckField.php
index 80365e7d8a2..673aea7f7de 100644
--- a/includes/htmlform/fields/HTMLCheckField.php
+++ b/includes/htmlform/fields/HTMLCheckField.php
@@ -1,7 +1,6 @@
 <?php
 
 use MediaWiki\Html\Html;
-use MediaWiki\MainConfigNames;
 use MediaWiki\Request\WebRequest;
 
 /**
@@ -16,11 +15,6 @@ class HTMLCheckField extends HTMLFormField {
 	 * @stable to override
 	 */
 	public function getInputHTML( $value ) {
-		$useMediaWikiUIEverywhere = false;
-		if ( $this->mParent ) {
-			$useMediaWikiUIEverywhere = $this->mParent->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere );
-		}
-
 		if ( !empty( $this->mParams['invert'] ) ) {
 			$value = !$value;
 		}
@@ -55,7 +49,7 @@ class HTMLCheckField extends HTMLFormField {
 			$chkDivider .
 			Html::rawElement( 'label', $attrLabel, $this->mLabel );
 
-		if ( $isCodexForm || $useMediaWikiUIEverywhere || $isVForm ) {
+		if ( $isCodexForm || $isVForm ) {
 			$chkLabelClass = $isCodexForm ? 'cdx-checkbox' : 'mw-ui-checkbox';
 			$chkLabel = Html::rawElement(
 				'div',
diff --git a/includes/htmlform/fields/HTMLCheckMatrix.php b/includes/htmlform/fields/HTMLCheckMatrix.php
index b6e03cbae07..80238138b81 100644
--- a/includes/htmlform/fields/HTMLCheckMatrix.php
+++ b/includes/htmlform/fields/HTMLCheckMatrix.php
@@ -1,7 +1,6 @@
 <?php
 
 use MediaWiki\Html\Html;
-use MediaWiki\MainConfigNames;
 use MediaWiki\Request\WebRequest;
 
 /**
@@ -184,14 +183,7 @@ class HTMLCheckMatrix extends HTMLFormField implements HTMLNestedFilterable {
 	}
 
 	protected function getOneCheckboxHTML( $checked, $attribs ) {
-		$checkbox = Xml::check( "{$this->mName}[]", $checked, $attribs );
-		if ( $this->mParent->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere ) ) {
-			$checkbox = Html::openElement( 'div', [ 'class' => 'mw-ui-checkbox' ] ) .
-				$checkbox .
-				Html::element( 'label', [ 'for' => $attribs['id'] ] ) .
-				Html::closeElement( 'div' );
-		}
-		return $checkbox;
+		return Xml::check( "{$this->mName}[]", $checked, $attribs );
 	}
 
 	protected function isTagForcedOff( $tag ) {
diff --git a/includes/htmlform/fields/HTMLMultiSelectField.php b/includes/htmlform/fields/HTMLMultiSelectField.php
index 1588badf2a0..b1754bafd65 100644
--- a/includes/htmlform/fields/HTMLMultiSelectField.php
+++ b/includes/htmlform/fields/HTMLMultiSelectField.php
@@ -1,7 +1,6 @@
 <?php
 
 use MediaWiki\Html\Html;
-use MediaWiki\MainConfigNames;
 use MediaWiki\Request\WebRequest;
 
 /**
@@ -145,11 +144,6 @@ class HTMLMultiSelectField extends HTMLFormField implements HTMLNestedFilterable
 					[ 'for' => $attribs['id'] ],
 					$label
 				);
-			if ( $this->mParent->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere ) ) {
-				$checkbox = Html::openElement( 'div', [ 'class' => 'mw-ui-checkbox' ] ) .
-					$checkbox .
-					Html::closeElement( 'div' );
-			}
 			return $checkbox;
 		}
 	}
diff --git a/includes/specialpage/SpecialPage.php b/includes/specialpage/SpecialPage.php
index 9ee38fce8c8..59661892c30 100644
--- a/includes/specialpage/SpecialPage.php
+++ b/includes/specialpage/SpecialPage.php
@@ -700,13 +700,6 @@ class SpecialPage implements MessageLocalizer {
 			$title = ( new RawMessage( '$1' ) )->rawParams( $title );
 		}
 		$out->setPageTitleMsg( $title );
-		if ( $this->getConfig()->get( MainConfigNames::UseMediaWikiUIEverywhere ) ) {
-			$out->addModuleStyles( [
-				'mediawiki.ui.input',
-				'mediawiki.ui.radio',
-				'mediawiki.ui.checkbox',
-			] );
-		}
 	}
 
 	/**
diff --git a/includes/xml/Xml.php b/includes/xml/Xml.php
index 126f337a7ab..f89fb6a8133 100644
--- a/includes/xml/Xml.php
+++ b/includes/xml/Xml.php
@@ -295,8 +295,7 @@ class Xml {
 			$attributes['value'] = $value;
 		}
 
-		return self::element( 'input',
-			Html::getTextInputAttributes( $attributes + $attribs ) );
+		return self::element( 'input', $attributes + $attribs );
 	}
 
 	/**
@@ -430,17 +429,9 @@ class Xml {
 	 * @return string HTML
 	 */
 	public static function checkLabel( $label, $name, $id, $checked = false, $attribs = [] ) {
-		$useMediaWikiUIEverywhere = MediaWikiServices::getInstance()->getMainConfig()
-			->get( MainConfigNames::UseMediaWikiUIEverywhere );
-		$chkLabel = self::check( $name, $checked, [ 'id' => $id ] + $attribs ) .
+		return self::check( $name, $checked, [ 'id' => $id ] + $attribs ) .
 			"\u{00A0}" .
 			self::label( $label, $id, $attribs );
-
-		if ( $useMediaWikiUIEverywhere ) {
-			$chkLabel = self::openElement( 'div', [ 'class' => 'mw-ui-checkbox' ] ) .
-				$chkLabel . self::closeElement( 'div' );
-		}
-		return $chkLabel;
 	}
 
 	/**
@@ -464,27 +455,17 @@ class Xml {
 	}
 
 	/**
-	 * Convenience function to build an HTML submit button
-	 * When $wgUseMediaWikiUIEverywhere is true it will default to a progressive button
+	 * Convenience function to build an HTML submit button.
+	 *
 	 * @param string $value Label text for the button (unescaped)
 	 * @param array $attribs Optional custom attributes
 	 * @return string HTML
 	 */
 	public static function submitButton( $value, $attribs = [] ) {
-		$useMediaWikiUIEverywhere = MediaWikiServices::getInstance()->getMainConfig()
-			->get( MainConfigNames::UseMediaWikiUIEverywhere );
-		$baseAttrs = [
+		$attribs += [
 			'type' => 'submit',
 			'value' => $value,
 		];
-		// Done conditionally for time being as it is possible
-		// some submit forms
-		// might need to be mw-ui-destructive (e.g. delete a page)
-		if ( $useMediaWikiUIEverywhere ) {
-			$baseAttrs['class'] = 'mw-ui-button mw-ui-progressive';
-		}
-		// Any custom attributes will take precedence of anything in baseAttrs e.g. override the class
-		$attribs += $baseAttrs;
 		return Html::element( 'input', $attribs );
 	}
 
@@ -657,14 +638,12 @@ class Xml {
 	 */
 	public static function textarea( $name, $content, $cols = 40, $rows = 5, $attribs = [] ) {
 		return self::element( 'textarea',
-					Html::getTextInputAttributes(
-						[
-							'name' => $name,
-							'id' => $name,
-							'cols' => $cols,
-							'rows' => $rows
-						] + $attribs
-					),
+					[
+						'name' => $name,
+						'id' => $name,
+						'cols' => $cols,
+						'rows' => $rows
+					] + $attribs,
 					$content, false );
 	}
 
diff --git a/tests/phpunit/includes/Html/HtmlTest.php b/tests/phpunit/includes/Html/HtmlTest.php
index 6a0a12905d8..20589f9e769 100644
--- a/tests/phpunit/includes/Html/HtmlTest.php
+++ b/tests/phpunit/includes/Html/HtmlTest.php
@@ -832,65 +832,6 @@ class HtmlTest extends MediaWikiIntegrationTestCase {
 		$this->assertSame( $expected, $html );
 	}
 
-	/** @dataProvider provideGetTextInputAttributes */
-	public function testGetTextInputAttributes(
-		bool $useMediaWikiUIEverywhere,
-		$classAttribute,
-		$expectedClassAttribute
-	) {
-		$this->overrideConfigValue( MainConfigNames::UseMediaWikiUIEverywhere, $useMediaWikiUIEverywhere );
-		$attrs = Html::getTextInputAttributes( [ 'class' => $classAttribute ] );
-		$this->assertSame( $expectedClassAttribute, $attrs['class'] );
-	}
-
-	public static function provideGetTextInputAttributes(): iterable {
-		yield 'MWUI everywhere, non-codex, class string' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => 'foo',
-			'expectedClassAttribute' => 'foo mw-ui-input',
-		];
-		yield 'MWUI everywhere, non-codex, class list' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => [ 'foo' ],
-			'expectedClassAttribute' => [ 'foo', 'mw-ui-input' => true ],
-		];
-		yield 'MWUI everywhere, non-codex, class dict' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => [ 'foo' => true ],
-			'expectedClassAttribute' => [ 'foo' => true, 'mw-ui-input' => true ],
-		];
-		yield 'MWUI everywhere, non-codex, class dict disables mw-ui-input' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => [ 'foo' => true, 'mw-ui-input' => false ],
-			'expectedClassAttribute' => [ 'foo' => true, 'mw-ui-input' => true ],
-		];
-		yield 'MWUI everywhere, codex, class string' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => 'foo cdx-text-input__input',
-			'expectedClassAttribute' => 'foo cdx-text-input__input',
-		];
-		yield 'MWUI everywhere, codex, class list' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => [ 'foo', 'cdx-text-input__input' ],
-			'expectedClassAttribute' => [ 'foo', 'cdx-text-input__input' ],
-		];
-		yield 'MWUI everywhere, codex, class dict' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => [ 'foo' => true, 'cdx-text-input__input' => true ],
-			'expectedClassAttribute' => [ 'foo' => true, 'cdx-text-input__input' => true ],
-		];
-		yield 'MWUI everywhere, class dict disables codex' => [
-			'useMediaWikiUIEverywhere' => true,
-			'classAttribute' => [ 'foo' => true, 'cdx-text-input__input' => false ],
-			'expectedClassAttribute' => [ 'foo' => true, 'cdx-text-input__input' => false, 'mw-ui-input' => true ],
-		];
-		yield 'not MWUI everywhere' => [
-			'useMediaWikiUIEverywhere' => false,
-			'classAttribute' => 'foo',
-			'expectedClassAttribute' => 'foo',
-		];
-	}
-
 	public static function provideEncodeJsVar() {
 		// $expected, $input
 		yield 'boolean' => [ 'true', true ];
diff --git a/tests/phpunit/includes/xml/XmlTest.php b/tests/phpunit/includes/xml/XmlTest.php
index 3ef708ad9f6..ebb53b4e1fe 100644
--- a/tests/phpunit/includes/xml/XmlTest.php
+++ b/tests/phpunit/includes/xml/XmlTest.php
@@ -15,7 +15,6 @@ class XmlTest extends MediaWikiIntegrationTestCase {
 
 		$this->overrideConfigValues( [
 			MainConfigNames::LanguageCode => 'en',
-			MainConfigNames::UseMediaWikiUIEverywhere => false,
 		] );
 
 		$langObj = $this->getServiceContainer()->getLanguageFactory()->getLanguage( 'en' );
@@ -77,21 +76,6 @@ class XmlTest extends MediaWikiIntegrationTestCase {
 		);
 	}
 
-	/**
-	 * @covers Xml::input
-	 * @covers \MediaWiki\Html\Html::getTextInputAttributes
-	 */
-	public function testInputWithMWUIEverywhere() {
-		$this->overrideConfigValues( [
-			MainConfigNames::UseMediaWikiUIEverywhere => true,
-		] );
-
-		$this->assertSame(
-			'<input name="name" class="foo mw-ui-input" />',
-			Xml::input( 'name', false, false, [ 'class' => 'foo' ] )
-		);
-	}
-
 	public function testOpenElement() {
 		$this->assertEquals(
 			'<element k="v">',