posts/til-expires-header.en.html

   1 <!-- subject: TIL: Browsers ignore <code>Expires</code> header on reload -->
   2 <!-- date: 2019-02-26 13:11:55 -->
   3 <!-- tags: expires, cache-control, http -->
   4 <!-- categories: Articles, Techblog -->
   5
   6 <p>This may have been obvious, but I’ve just learned that browsers
   7   ignore <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Expires">Expires</a>
   8   header when the user manually reloads the page (as in by pressing F5 or
   9   choosing Reload option).
  10
  11 <p>I’ve run into this when testing how Firefox treats pages which ‘never’
  12   expire.  To my surprise, the browser made requests for files it had a fresh
  13   copy of in its cache.  To see behaviour much more representative of the
  14   experience of a returning user, one should select the address bar (Alt+D does
  15   the trick) and then press Return to navigate to the current page again.
  16   Hitting Reload is more akin, though not exactly the same, to the first visit.
  17
  18 <p>Of course, all of the above applies to the <code>max-age</code> directive of
  19   the <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control">Cache-Control</a>
  20   header as well.
  21
  22 <p>Moral of the story? Make sure you test the actual real-life scenarios before
  23   making any decisions.
  24
  25 <!-- COMMENT -->
  26 <!-- date: 2019-07-10 19:51:16 -->
  27 <!-- nick: Alex Rudenko -->
  28 <!-- nick_url: https://twitter.com/orKoN -->
  29 <!-- nick_email: nyrkrv.ehqraxb@tznvy.pbz -->
  30
  31 <p>I often have problems with cache invalidation in the browsers especially if I use service workers. The latest problem for me was that the browser wouldn't not refresh even on reload because of a badly written service worker.