Comments on: F5 and XHR deep dive

By: Ionatan Wiznia

Ionatan Wiznia — Tue, 16 Feb 2010 15:59:53 +0000

Alert developers!
This is also true for scripts if you load them via dom:
var element = document.createElement(“script”);
element.setAttribute(“type”, “text/javascript”);
element.src = ‘srcofthescript’;
document.body.appendChild(element);

By: vincent voyer

vincent voyer — Mon, 11 Jan 2010 15:54:55 +0000

I would say to never use ctrl+f5 when testing a web app because it triggers some very strange behavior on FF.

It will download all ressources every time you want to access it, without using cache ever, unless you do a simple f5 or better, open a new tab (or empty cache).

Empty your cache and hit ctrl+f5 gives two different behavior on FF.

Do not use ctrl+f5 :)

By: Dudy Adityawan

Dudy Adityawan — Sun, 06 Sep 2009 16:26:34 +0000

My Friend this article really useful. Thanks. Wondering what you find when the browser is closed. I seem to inconsistently find that some pages even with future expires are not cached when the browser is closed.

By: David King

David King — Sat, 22 Aug 2009 16:33:54 +0000

Great article again Steve, although I’m more enamoured by the Yahoo best preactices page you’ve linked to… how have I missed that?

By: Morgan Cheng

Morgan Cheng — Fri, 14 Aug 2009 23:39:13 +0000

As a web developer, I found the F5 and Ctrl-F5 behavior is different in Firefox against IE. It’s not guaranteed to reload external javascript files from a page when hitting F5 in Firefox(both in 2.x and 3.x).

I once programmed something and tested it in Firefox. After hitting F5 or Ctrl-F5, the updated external javascript doesn’t get reloaded, even it is local.

Steve, can you give another article about behavior of F5 and Ctrl-F5 in different browsers?

By: Martin

Martin — Fri, 14 Aug 2009 12:48:57 +0000

To solve this issue on IE we use ETags on XHR.

Good article Steave, thanks

By: Anup

Anup — Wed, 12 Aug 2009 19:42:11 +0000

Sorry — should have clarified a bit more — I find inconsistencies amongst different browsers and different sites (sites I can understand as some sites set future expiring dates etc, but on many browser I often see even future expiring items being rerequested when visited after the browser is re-opened).

The other consideration is closing browsers such that they do not re-open the same tabs that were just closed (as that always seems to come from cache).

By: Anup

Anup — Wed, 12 Aug 2009 19:40:16 +0000

Steve, this is really useful. Thanks. Wondering what you find when the browser is closed. I seem to inconsistently find that some pages even with future expires are not cached when the browser is closed, and all content is re-requested from the server.

By: Mats

Mats — Wed, 12 Aug 2009 17:34:06 +0000

Sorry, I meant control-shift-R but I guess it’s the same as ctrl-f5 (only less work for your hand hehe :)

Might be worth a try.

By: Steve Souders

Steve Souders — Wed, 12 Aug 2009 16:13:03 +0000

@edvakf: I’m using Safari 4.0, the current version of Safari, but still don’t see the IMS header.

@Mats: Ctrl-R is the same as F5 – it uses what’s in the cache and sends the If-Modified-Since header. (Tested on IE7 and FF3.5.)

@Joao: I didn’t test POST because they’re bad for performance – they require an extra packet to complete the request.