Pragma header will be ignored if Cache-Control is specified


Categories: Networking

Releases: Firefox 80


Previously in Firefox, the Pragma HTTP/1.0 response header had precedence over the Cache-Control HTTP/1.1 response header, even though the former is used only for backward compatibility with older HTTP/1.0 clients.

During a performance enhancement work, Mozilla developers found that some stylesheets on eBay were not cached because of a conflict between the two headers where Cache-Control allowed to cache them while Pragma:no-cache didn’t. Aiming to avoid similar issues, Firefox 80 and later will ignore the legacy Pragma header if the Cache-Control header is specified.

It’s probably time to drop Pragma, given that all modern browsers support HTTP/2, and HTTP/3 is also coming soon.