How Does a Web Cache Work?
A Web cache is a mechanism whereby frequently accessed Web objects, including HTML pages, images and sounds, are stored temporarily in a location where they can be accessed quickly. If you visit the same Web page a second time, any objects that you viewed or downloaded the first time around can be loaded from the Web cache, rather than being downloaded from the Web server again.
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Browser Cache
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There are essentially two types of Web cache -- a browser cache and a proxy cache. A browser cache is a part of all popular Web browsers, such as Microsoft Internet Explorer, Mozilla Firefox and Google Chrome. The first time you request a Web page, the browser not only renders the page, but also stores a copy of the page in a special folder on the local hard drive. The next time you request the same page, the browser compares the date of the Web page with that of the cached page; if the date is the same, the browser loads the cached page rather than downloading it from the Web.
Proxy Cache
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A browser cache stores Web pages locally on an individual computer. But if multiple users on a network access similar websites, the second type of cache, known as a proxy cache, may be more appropriate. A proxy cache is a shared network device, but otherwise works in much the same way as a browser cache. The client computer opens a session with the proxy cache using the HTTP -- the formal set of rules for transferring documents on the Web -- and directs Web requests to the proxy cache rather than the Web server. If the requested page exists in the proxy cache, it is checked for freshness and, if fresh, delivered to the client. If the requested page cannot be found in the proxy cache, or is stale, the proxy cache establishes its own session with the Web server and attempts to copy the Web page.
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Purpose
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Web caching improves the quality of service for many types of Web user. It is widely employed by Internet Service Providers worldwide because it not only reduces the perceived delay, or lag, in delivering Web content to end users, but also reduces bandwidth consumption and server load; if Web requests are satisfied by nearby Web caches, less network traffic moves between Web servers and end users.
Disabling Web Caching
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Web caching typically makes a Web browser faster, simply because it takes less time to retrieve the elements of a Web page, or even the entire page, from a browser or proxy cache than it does to download the page from the Web. However, there may be occasions -- if you’re doing Web development, for example -- when you want to disable Web caching, so that you always see the most up-to-date version of a Web page.
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References
- Photo Credit John Foxx/Stockbyte/Getty Images
