caching - How does the browser know a web page has changed? -

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This is a dangerous thing that I think I should know more about it - but I do not, More can not be found

The question is: How exactly does a web page know that a web page has changed?

In the interpolation I would say that F5 refreshes the cache for one given page, and this cache history is used only for navigation and its expiry date is - I It seems that the browser never knows if a web page has changed, and this page reloads the end of the cache --- but I'm sure this is not always the case.

Appreciate any pointers!

Browsers will usually receive this information through the HTTP header sent with the page

For example, the last-modified header tells the browser how old a page is, that a browser can send a simple head request to the page to get the last modified value. If this is newer than the browser in the cache, then the browser can reload it.

Check out a bunch of other headers related to caching (like cash-control):


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