Various web page resources such as images or CSSfiles can be stored temporarily in the Cache of a browser in order to speed up the retrieval of web pages. A Cache validator is used to check whether the stored information is still up-to-date.
What is a Cache validator?
A Cache validator is an HTTP header used to check whether resources stored in a browser cache are still valid. This check is performed when a web page is retrieved. For this purpose, the validator can be inserted and defined in the HTTP request or response header.
The positive effect
Validating the Cache content is important to significantly reduce the loading time of a website. If the resources are up-to-date, they do not have to be downloaded from the server, but can be provided much faster from the Cache.
Types of header
There are four different headers available for Cache validation. The last-modified and ETag headers are used to determine if a file stored in the browserCache has changed since the last time the web page was accessed. The last-modified header is sent by default and automatically by servers, so this validator does not need to be specifically included in an HTML document. Two other headers – “cache-control” and “expires” – are used to determine how long a resource should be stored in Cache before it needs to be replaced by a new version, which is then retrieved from the server.
Also of importance to you may be Last-modified – part of an http header. Here you can learn more:To the article
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