Quick note: If you are serving HTML/CSS/JS/Any image files via AWS S3 with Cloudfront, but got 503 error, here is one way to solve: Simply put: In Viewer request, set cloudfront function to "serve-html-by-s3" Set Viewer repsonse to "No association" Setting Viewer response to value other than "No association" will result in 503 error. Hope it helps someone.