Kind of unrelated; But maybe someone knows.

Michael Shadle mike503 at
Thu Dec 23 03:49:14 MSK 2010

On Wed, Dec 22, 2010 at 4:43 PM, David J. <david at> wrote:

> I was wondering why some sites have
> <script src="path/to/javascript.js?432532432"></script>
> What is the "?432532432" or whatever used for? Is it a versioning thing.
> I see it on many of the bigger sites.
> <link href="/css/layout.css?1291917579" media="all" rel="stylesheet">
> Thanks for any info.

Forces the user's browser to treat the same on the server as a
different one. Or, a lot of the time, CDNs - a technique known as
"cache busting"

It will force a browser and most CDNs to re-cache the file as a fresh
copy as it includes the query string as part of the key. Otherwise due
to Expires headers, CDNs and other caching behavior, clients wouldn't
know that a new copy of a specific file might be fresh.

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