Force browser to clear cache

Question

Is there a way I can put some code on my page so when someone visits a site, it clears the browser cache, so they can view the changes?

Languages used: ASP.NET, VB.N

Answer 1

Not sure if that might really help you but that's how caching should work on any browser. When the browser request a file, it should always send a request to the server unless there is a "offline" mode. The server will read some parameters like date modified or etags.

The server will return a 304 error response for NOT MODIFIED and the browser will have to use its cache. If the etag doesn't validate on server side or the modified date is below the current modified date, the server should return the new content with the new modified date or etags or both.

If there is no caching data sent to the browser, I guess the behavior is undetermined, the browser may or may not cache file that don't tell how they are cached. If you set caching parameters in the response it will cache your files correctly and the server then may choose to return a 304 error, or the new content.

This is how it should be done. Using random params or version number in urls is more like a hack than anything.

http://www.checkupdown.com/status/E304.html http://en.wikipedia.org/wiki/HTTP_ETag http://www.xpertdeveloper.com/2011/03/last-modified-header-vs-expire-header-vs-etag/

After reading I saw that there is also a expire date. If you have problem, it might be that you have a expire date set up. In other words, when the browser will cache your file, since it has a expiry date, it shouldn't have to request it again before that date. In other words, it will never ask the file to the server and will never receive a 304 not modified. It will simply use the cache until the expiry date is reached or cache is cleared.

So that is my guess, you have some sort of expiry date and you should use last-modified etags or a mix of it all and make sure that there is no expire date.

If people tends to refresh a lot and the file doesn't get changed a lot, then it might be wise to set a big expiry date.

My 2 cents!