diff --git a/inc/Addon/WebP/Subscriber.php b/inc/Addon/WebP/Subscriber.php
index 4ff207d5d5..6507620886 100644
--- a/inc/Addon/WebP/Subscriber.php
+++ b/inc/Addon/WebP/Subscriber.php
@@ -435,14 +435,20 @@ private function url_to_webp( $url, $extensions ) {
 
 		if ( $this->filesystem->exists( $src_path_webp ) ) {
 			// File name: image.jpg => image.webp.
-			return preg_replace( '@\.' . $src_url['extension'] . '$@', '.webp', $src_url['src'] ) . $src_url['query'];
+			$src_url_webp = preg_replace( '@\.' . $src_url['extension'] . '$@', '.webp', $src_url['src'] ) . $src_url['query'];
+		} elseif ( $this->filesystem->exists( $src_path_webp = $src_path . '.webp' ) ) { // phpcs:ignore Generic.Sniffs.CodeAnalysis.AssignmentInCondition,Squiz.Sniffs.PHP.DisallowMultipleAssignments
+			// File name: image.jpg => image.jpg.webp.
+			$src_url_webp = $src_url['src'] . '.webp' . $src_url['query'];
+		} else {
+			// No webp exists.
+			return false;
 		}
 
-		if ( $this->filesystem->exists( $src_path . '.webp' ) ) {
-			// File name: image.jpg => image.jpg.webp.
-			return $src_url['src'] . '.webp' . $src_url['query'];
+		if ( $this->filesystem->size( $src_path_webp ) < $this->filesystem->size( $src_path ) ) {
+			return $src_url_webp;
 		}
 
+		// The webp isn't smaller than the original, so don't use it.
 		return false;
 	}