A common technique here is to use the query string to control this, with something like ?t=‹timestamp› or ?v=‹version› or ?‹hash of file contents›. Then the ser

A common technique here is to use the query string to control this, with something like ?t=‹timestamp› or ?v=‹version› or ?‹hash of file contents›. Then the server can include proper cache-control headers to say “this is immutable, never going to change, don’t bother asking me if it’s changed”. A cachebust="yes" attribute wouldn’t be useful in practice because the server would either be serving it to everyone, effectively disabling caching (and which would be better done by actually disabling caching with the cache-control header), or need to decide who to serve the attribute to, in which case there are better solutions. In short, cache busting only works if you have some sort of cache key, which is what the query string technique is all about doing.