Asset File Caching
Modern web framework asset handling often renames files with distinct fingerprints or means of assisting with asset caching. If those aren't available in your framework, you'll need to manually clear the cache after deploying your application.
Asset file extensions
Files served by your Heroku application that end in any of the following file extensions are considered assets and are cached for 3 days:
js, css, png, swf, jpg, jpeg, svg, svz, gif, ico, mp3, mp4, odf, pdf, woff, woff2, ttf, thumb, webp, txt, otf, 7z, aac, ai, asf, avi, bmp, bz2, doc, docx, eot, eps, fla, flv, gz, ind, m4a, m4v, mkv, mko, mpeg, oga, ogx, pptx, psd, rar, rtf, tar, tgz, tiff, wav, xlsx, xml, zip, zipx
Versioning cache URLs
Expedited WAF considers URL parameters to be distinct resources for caching. This means that:
are distinct, and requesting the second does not return the cached results for the first. You can use this to version URLs within your application by appending different URL parameters to any URL that you need not to be cached.