diff --git a/Tests/Integration/inc/functions/imagifyGetMimeTypes.php b/Tests/Integration/inc/functions/imagifyGetMimeTypes.php
new file mode 100644
index 000000000..edd6608ee
--- /dev/null
+++ b/Tests/Integration/inc/functions/imagifyGetMimeTypes.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Imagify\Tests\Integration\Functions;
+
+use Imagify\Tests\Integration\TestCase;
+
+class Test_ImagifyGetMimeTypes extends TestCase {
+	protected $useApi = false;
+
+	public function testShouldReturnAllMimeTypesByDefault() {
+		$this->assertSame(
+			[
+				'jpg|jpeg|jpe' => 'image/jpeg',
+				'png'          => 'image/png',
+				'gif'          => 'image/gif',
+				'webp'         => 'image/webp',
+				'pdf'          => 'application/pdf',
+			],
+			imagify_get_mime_types()
+		);
+	}
+
+	public function testShouldReturnImageMimeTypesOnly() {
+		$this->assertSame(
+			[
+				'jpg|jpeg|jpe' => 'image/jpeg',
+				'png'          => 'image/png',
+				'gif'          => 'image/gif',
+				'webp'         => 'image/webp',
+			],
+			imagify_get_mime_types( 'image' )
+		);
+	}
+
+	public function testShouldReturnNotImageMimeTypesOnly() {
+		$this->assertSame(
+			[ 'pdf' => 'application/pdf' ],
+			imagify_get_mime_types( 'not-image' )
+		);
+	}
+
+	public function testShouldApplyMimeTypesFilter() {
+		$callback = function ( $mimes ) {
+			$mimes['avif'] = 'image/avif';
+			unset( $mimes['pdf'] );
+
+			return $mimes;
+		};
+
+		add_filter( 'imagify_get_mime_types', $callback );
+
+		$mimes = imagify_get_mime_types();
+
+		remove_filter( 'imagify_get_mime_types', $callback );
+
+		$this->assertSame( 'image/avif', $mimes['avif'] );
+		$this->assertArrayNotHasKey( 'pdf', $mimes );
+	}
+
+	public function testShouldDiscardMalformedFilteredMimeTypes() {
+		$callback = function ( $mimes ) {
+			$mimes['bad-bool']  = true;
+			$mimes['bad-array'] = [ 'image/png' ];
+			$mimes['not-mime']  = 'image';
+
+			return $mimes;
+		};
+
+		add_filter( 'imagify_get_mime_types', $callback );
+
+		$mimes = imagify_get_mime_types();
+
+		remove_filter( 'imagify_get_mime_types', $callback );
+
+		$this->assertArrayNotHasKey( 'bad-bool', $mimes );
+		$this->assertArrayNotHasKey( 'bad-array', $mimes );
+		$this->assertArrayNotHasKey( 'not-mime', $mimes );
+		$this->assertSame( 'image/jpeg', $mimes['jpg|jpeg|jpe'] );
+	}
+}
diff --git a/Tests/Unit/inc/functions/imagifyGetMimeTypes.php b/Tests/Unit/inc/functions/imagifyGetMimeTypes.php
new file mode 100644
index 000000000..8e42edc20
--- /dev/null
+++ b/Tests/Unit/inc/functions/imagifyGetMimeTypes.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Imagify\Tests\Unit\Functions;
+
+use Brain\Monkey\Filters;
+use Imagify\Tests\Unit\TestCase;
+
+class Test_ImagifyGetMimeTypes extends TestCase {
+	/**
+	 * Test should return image mime types and PDF when no type is given.
+	 */
+	public function testShouldReturnAllMimeTypesByDefault() {
+		$this->assertSame(
+			[
+				'jpg|jpeg|jpe' => 'image/jpeg',
+				'png'          => 'image/png',
+				'gif'          => 'image/gif',
+				'webp'         => 'image/webp',
+				'pdf'          => 'application/pdf',
+			],
+			imagify_get_mime_types()
+		);
+	}
+
+	/**
+	 * Test should return only image mime types for the image type.
+	 */
+	public function testShouldReturnImageMimeTypesOnly() {
+		$this->assertSame(
+			[
+				'jpg|jpeg|jpe' => 'image/jpeg',
+				'png'          => 'image/png',
+				'gif'          => 'image/gif',
+				'webp'         => 'image/webp',
+			],
+			imagify_get_mime_types( 'image' )
+		);
+	}
+
+	/**
+	 * Test should return only PDF for the not-image type.
+	 */
+	public function testShouldReturnNotImageMimeTypesOnly() {
+		$this->assertSame(
+			[ 'pdf' => 'application/pdf' ],
+			imagify_get_mime_types( 'not-image' )
+		);
+	}
+
+	/**
+	 * Test should pass the mime types through the imagify_get_mime_types filter.
+	 */
+	public function testShouldApplyMimeTypesFilter() {
+		Filters\expectApplied( 'imagify_get_mime_types' )
+			->once()
+			->andReturn( [ 'avif' => 'image/avif' ] );
+
+		$this->assertSame( [ 'avif' => 'image/avif' ], imagify_get_mime_types() );
+	}
+
+	/**
+	 * Test should discard malformed entries returned by the filter.
+	 */
+	public function testShouldDiscardMalformedFilteredMimeTypes() {
+		Filters\expectApplied( 'imagify_get_mime_types' )
+			->once()
+			->andReturn(
+				[
+					'avif'      => 'image/avif',
+					'bad-bool'  => true,
+					'bad-array' => [ 'image/png' ],
+					'not-mime'  => 'image',
+					0           => 'image/gif',
+					''          => 'image/jpeg',
+				]
+			);
+
+		$this->assertSame( [ 'avif' => 'image/avif' ], imagify_get_mime_types() );
+	}
+}
diff --git a/inc/functions/attachments.php b/inc/functions/attachments.php
index 0bf6f3242..f5fa22e6c 100755
--- a/inc/functions/attachments.php
+++ b/inc/functions/attachments.php
@@ -26,7 +26,23 @@ function imagify_get_mime_types( $type = null ) {
 		$mimes['pdf'] = 'application/pdf';
 	}
 
-	return $mimes;
+	/**
+	 * Filter the mime types which could be optimized by Imagify.
+	 *
+	 * @since 2.3.1
+	 *
+	 * @param array $mimes The mime types, as extension => mime type pairs.
+	 */
+	$mimes = wpm_apply_filters_typed( 'array', 'imagify_get_mime_types', $mimes );
+
+	// Keep only well-formed extension => mime type pairs.
+	return array_filter(
+		$mimes,
+		function ( $mime, $ext ) {
+			return is_string( $ext ) && '' !== $ext && is_string( $mime ) && preg_match( '@^[a-z-]+/[a-z0-9.+-]+$@', $mime );
+		},
+		ARRAY_FILTER_USE_BOTH
+	);
 }
 
 /**