Browser cache is a buffer memory of the web browser in which resources that have already been retrieved (e.g. text or images) are stored on the user’s computer (locally) as a copy. If a resource is needed again later, it can be retrieved from the cache more quickly than if it had to be downloaded again from the World Wide Web.
Every time the content of a URL is needed to display a page, the first thing it does is check in the cache to see if it already exists. The advantage is that network traffic and the time it takes to download all components of a web page are greatly reduced. The disadvantage is that the data stored in the cache may be outdated if the website has been updated in the meantime.
Browser Cache: Areas of Application
“Resource” is anything that can be accessed from a specific URL. At different times, different content may be present at the same URL. In the cache, each URL is associated with the most recently known content. The same concept for a browser cache on a user’s PC is also used by so-called proxy servers for entire computer networks, for example for a company location or a university at the connection point to the Internet, or for all customers of a (physical) telecommunications provider in a coverage area. They deliver frequently requested files directly to all connected participants of this network, without having to go through the actual Internet first.
Caching can basically be used for any protocol that makes resources available. In practice, however, it is only used for HTTP/HTTPS. If you request a file download via FTP using your browser, you will receive a fresh version at that moment; however, a proxy server could keep copies of frequently requested files. sends data and does not retrieve it. Other protocols for resources don’t offer much support for version management, and they’re not widely used today.
For a browser, users generally have the following options for influencing the behavior of the cache through configuration settings or interactively:
- Set the maximum amount of disk space; at zero, there is no caching.
- Retrieving the current page from the server (would affect the URL visible in the address bar; single page, or a graphic).
- Reload the current page and all resources included in it (images, scripts, styles, etc.) (this would usually only apply to HTML pages).
- Clear the entire cache, possibly selectively only for all resources of a specific domain (the current page).
- At the end (or alternatively at the beginning) of each session, clear the entire cache.
- Set the maximum age for resources.