diff --git a/.circleci/template.yml b/.circleci/template.yml
index a45cea8825b..8c74d3fc8eb 100644
--- a/.circleci/template.yml
+++ b/.circleci/template.yml
@@ -24,7 +24,7 @@ commands:
               echo "Running full flow due to nightly build, despite detecting '[short flow]'."
               exit 0
             fi
-            
+
             if [[ "$COMMIT_MESSAGE" == *"[short flow]" ]]; then
               echo "Skipping, because the commit message contains '[short flow]'."
               circleci step halt
@@ -105,6 +105,10 @@ jobs:
           when: always
           name: Validate icons specified in "ckeditor5-metadata.json" files
           command: node scripts/ci/validate-metadata-icons.js
+      - run:
+          when: always
+          name: Check if all SVG files are optimized
+          command: yarn run clean-up-svg-icons --verify-only
       - run:
           when: always
           name: Validate manual test directories
diff --git a/scripts/clean-up-svg-icons.js b/scripts/clean-up-svg-icons.js
index 672b70c148b..9b6f6dd7abf 100644
--- a/scripts/clean-up-svg-icons.js
+++ b/scripts/clean-up-svg-icons.js
@@ -10,20 +10,37 @@
 // Cleans up and optimizes SVG files using the SVGO utility. The configuration file is located in svgo.config.json.
 //
 // Usage:
-// 	yarn run clean-up-svg-icons <path/to/icons>
+// 	yarn run clean-up-svg-icons [<option>...] [<path>...]
 //
-// 	yarn run clean-up-svg-icons <path/to/icons> <another/path/to/icons>
-//
-// The <path/to/icons> can be either a direct path to a SVG file, or a path to a directory. Glob patterns in path are supported.
+// The <path> can be either a direct path to a SVG file, or a path to a directory. Glob patterns in path are supported.
 // Multiple arguments (paths) in one call are supported.
 //
-// To optimize the entire project run:
-// 	yarn run clean-up-svg-icons
+// Options:
+// 	--verify-only
+// 		If set, the script does not modify any SVG file, but it checks whether all files are already optimized.
+// 		If any file is not optimized, the script ends with an error code.
+//
+// Examples:
+// 	To optimize the entire project, run:
+// 		yarn run clean-up-svg-icons
+//
+// 	To optimize single file, run:
+// 		yarn run clean-up-svg-icons <path/to/icon>
+//
+// 	To optimize single directory, run:
+// 		yarn run clean-up-svg-icons <path/to/directory>
+//
+// 	To optimize multiple directories, run:
+// 		yarn run clean-up-svg-icons <path/to/directory> <another/path/to/directory>
+//
+// 	To check if single file is already optimized, run:
+// 		yarn run clean-up-svg-icons --verify-only <path/to/icon>
 
 'use strict';
 
 const chalk = require( 'chalk' );
 const upath = require( 'upath' );
+const fs = require( 'fs-extra' );
 const minimist = require( 'minimist' );
 const { globSync } = require( 'glob' );
 const { execSync } = require( 'child_process' );
@@ -38,33 +55,82 @@ const EXCLUDED_ICONS = [
 // A pattern to match all the icons.
 const ALL_ICONS_PATTERN = 'packages/**/theme/icons';
 
-const globPattern = parseArguments( process.argv.slice( 2 ) )
-	.map( pathToIcon => pathToIcon.endsWith( '.svg' ) ? pathToIcon : pathToIcon + '/*.svg' );
+const { paths, verifyOnly } = parseArguments( process.argv.slice( 2 ) );
+
+const globPattern = paths.map( pathToIcon => {
+	return pathToIcon.endsWith( '.svg' ) ? pathToIcon : pathToIcon + '/*.svg';
+} );
+
+let statusCode = 0;
 
 globSync( globPattern )
 	.map( upath.toUnix )
-	.filter( pathToIcon => {
-		const iconName = upath.basename( pathToIcon );
-		const isExcluded = EXCLUDED_ICONS.includes( iconName );
+	.filter( filterExcludedIcons )
+	.forEach( processIcon );
+
+if ( verifyOnly && statusCode ) {
+	console.log( chalk.red.bold( '\nSome SVG files are not optimized.' ) );
+	console.log( chalk.red(
+		'Execute "yarn run clean-up-svg-icons" to optimize them or add them to exceptions in "scripts/clean-up-svg-icons.js" file.\n'
+	) );
+
+	process.exit( statusCode );
+}
+
+function parseArguments( args ) {
+	const config = {
+		boolean: [
+			'verify-only'
+		],
 
-		if ( isExcluded ) {
-			console.log( chalk.yellow( `The "${ pathToIcon }" icon is excluded.` ) );
+		default: {
+			'verify-only': false
 		}
+	};
 
-		return !isExcluded;
-	} )
-	.forEach( pathToIcon => {
-		console.log( chalk.green( `Processing "${ pathToIcon }" icon...` ) );
+	const {
+		'verify-only': verifyOnly,
+		_: paths
+	} = minimist( args, config );
 
-		execSync( `svgo --config=./scripts/svgo.config.js -i ${ pathToIcon }` );
-	} );
+	return {
+		verifyOnly,
+		paths: paths.length > 0 ? paths : [ ALL_ICONS_PATTERN ]
+	};
+}
 
-function parseArguments( args ) {
-	const paths = minimist( args )._;
+function filterExcludedIcons( pathToIcon ) {
+	const iconName = upath.basename( pathToIcon );
+	const isExcluded = EXCLUDED_ICONS.includes( iconName );
 
-	if ( paths.length > 0 ) {
-		return paths;
+	if ( isExcluded ) {
+		console.log( chalk.yellow( `The "${ pathToIcon }" icon is excluded.` ) );
 	}
 
-	return [ ALL_ICONS_PATTERN ];
+	return !isExcluded;
+}
+
+function processIcon( pathToIcon ) {
+	console.log( chalk.green( `Processing "${ pathToIcon }" icon...` ) );
+
+	const svgoOptions = [
+		'--config=./scripts/svgo.config.js',
+		`-i ${ pathToIcon }`
+	];
+
+	if ( verifyOnly ) {
+		svgoOptions.push( '-o -' );
+	}
+
+	const result = execSync( `svgo ${ svgoOptions.join( ' ' ) }`, { encoding: 'utf-8' } ).trim();
+
+	if ( verifyOnly ) {
+		const iconFile = fs.readFileSync( pathToIcon, 'utf-8' ).trim();
+
+		if ( result !== iconFile ) {
+			statusCode = 1;
+
+			console.log( chalk.red( `Icon "${ pathToIcon }" is not optimized.` ) );
+		}
+	}
 }