# Kind of unrelated; But maybe someone knows

**URL:** <https://www.ruby-forum.com/t/kind-of-unrelated-but-maybe-someone-knows/200835>\
**Category:** NGINX\
**Created:** [December 23, 2010, 1:43am UTC](https://www.ruby-forum.com/t/kind-of-unrelated-but-maybe-someone-knows/200835 "2010-12-23T01:43:33Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![nikuSESS](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/f17d59/32.png) [@nikuSESS](https://www.ruby-forum.com/u/nikuSESS)\
**Post date:** [December 23, 2010, 1:43am UTC](https://www.ruby-forum.com/t/kind-of-unrelated-but-maybe-someone-knows/200835/1 "2010-12-23T01:43:33Z")

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I was wondering why some sites have

What is the “?432532432” or whatever used for? Is it a versioning thing.

I see it on many of the bigger sites.

Thanks for any info.

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**Author:** ![elegant](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/3ab097/32.png) [@elegant](https://www.ruby-forum.com/u/elegant)\
**Post date:** [December 23, 2010, 1:50am UTC](https://www.ruby-forum.com/t/kind-of-unrelated-but-maybe-someone-knows/200835/2 "2010-12-23T01:50:27Z")

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On Wed, Dec 22, 2010 at 4:43 PM, David J. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> 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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**Author:** ![elegant](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/3ab097/32.png) [@elegant](https://www.ruby-forum.com/u/elegant)\
**Post date:** [December 23, 2010, 1:58am UTC](https://www.ruby-forum.com/t/kind-of-unrelated-but-maybe-someone-knows/200835/3 "2010-12-23T01:58:35Z")

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Thanks mike;

Would you happen to have any articles or information that goes deeper  
into that?

I understand the concept clearly; Obviously on CSS or JS files are any  
versioned content; You wouldnt want that data cached;

But I never saw the technique mentioned before; So I would like to  
learn a bit more about it.

Thanks Again.

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**Author:** ![elegant](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/3ab097/32.png) [@elegant](https://www.ruby-forum.com/u/elegant)\
**Post date:** [December 24, 2010, 8:51am UTC](https://www.ruby-forum.com/t/kind-of-unrelated-but-maybe-someone-knows/200835/4 "2010-12-24T08:51:48Z")

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On 12/22/2010 09:58 PM, David J. wrote:

> Would you happen to have any articles or information that goes deeper  
> into that?

Search “cache busting” on the net.

> I understand the concept clearly; Obviously on CSS or JS files are any  
> versioned content; You wouldnt want that data cached;

You could see it basically as a reload mechanism. You modified the  
site’s CSS/JS, and append some timestamp to the query string so the file  
gets reloaded on the next page view, and cached by the browser (and  
possibly the web server). This is to avoid that your visitors need to  
reload the page contents to see the stuff you edited on those files.

The query string would remain the same until you modify these files  
again.

> But I never saw the technique mentioned before; So I would like to learn  
> a bit more about it.

It’s like uniqid() some of us use on captcha’s images, but made for last  
a bit longer.

Regards