I have noticed that some browsers (in particular, Firefox and [Opera][1]) are very zealous in using cached copies of **.css** and **.js** files, even between browser sessions. This leads to a problem when you update one of these files, but the user&#39;s browser keeps on using the cached copy.

What is the most elegant way of forcing the user&#39;s browser to reload the file when it has changed?

Ideally, the solution would not force the browser to reload the file on every visit to the page.

&lt;hr/&gt;

I have found [John Millikin&#39;s][2] and [da5id&#39;s][3] suggestion to be useful. It turns out there is a term for this: **auto-versioning**.

I have posted a new answer below which is a combination of my original solution and John&#39;s suggestion.

Another idea that was suggested by **SCdF** would be to append a bogus query string to the file. (Some Python code, to automatically use the timestamp as a bogus query string, was [submitted by *pi.*][4].)

However, there is some discussion as to whether or not the browser would cache a file with a query string. (Remember, we want the browser to cache the file and use it on future visits. We only want it to fetch the file again when it has changed.)


  [1]: https://en.wikipedia.org/wiki/Opera_%28web_browser%29
  [2]: https://stackoverflow.com/questions/118884/how-to-force-the-browser-to-reload-cached-css-and-javascript-files/118921#118921
  [3]: https://stackoverflow.com/questions/118884/how-to-force-the-browser-to-reload-cached-css-and-javascript-files/118901#118901
  [4]: https://stackoverflow.com/questions/118884/how-to-force-the-browser-to-reload-cached-css-and-javascript-files/121143#121143

All Auto Versioning Solutions on Gang of Coders

Total of 1 Auto Versioning Solutions

How to force the browser to reload cached CSS and JavaScript files