This article is about an efficient technique of caching static resources on the client side (user's browser). There are quite many ways to implement caching including HTTP headers. A common disadvantage of them is that as soon as some resource is cached by the browser, it won't be updated until it's expired. Thus, the server loses control over the browser caching mechanism for some period of time. As a result we have to adjust the expiration time period or updating frequency somehow. The better alternative is the case when it's only the server that is in charge of the browser caching mechanism. Actually the idea has been borrowed here . If we append a GET parameter with some changing value (like a timestamp or a version) for a static resource URL, it'll force the browser to get the fresh version of the resource from the server. If we keep the parameter value steady, the resource will be taken from the browser cache. Finally this article is about implementation.