tl;dr if they’re not using Firefox you can send them a Clear-Site-Data: “cache” header from the same origin.

e.g. in PHP, send them a header

header('Clear-Site-Data: "cache"');

This can be on its own standalone URL, e.g. – it clears cache for the origin, in this case



Firefox doesn’t support this header yet.

Open Dev tools, turn caching off, visit the cached redirect URL again, cache should be cleared.