Which etags

Strong and weak ETag validation The ETag mechanism supports both strong validation and weak validation. About the Author: Avinash. Alex March 25, at pm - Reply. Cheatsheet: NET March 31, at pm - Reply. WordPress Wordpresso December 21, at pm - Reply. Leave A Comment Cancel reply.

Apache: add the following line to your main Apache configuration file or the. Share this article. We use cookies to ensure that we give you the best experience on our website. Please accept cookies for optional performance. Accept Privacy policy. If a user visits a given URL again that has an ETag set , and it is stale too old to be considered usable , the client will send the value of its ETag along in an If-None-Match header field:.

The server compares the client's ETag sent with If-None-Match with the ETag for its current version of the resource, and if both values match that is, the resource has not changed , the server sends back a Not Modified status, without a body, which tells the client that the cached version of the response is still good to use fresh.

Header type Response header Forbidden header name no. For example, when editing a wiki, the current wiki content may be hashed and put into an Etag header in the response: ETag: "33a64dffcc55e4d42ad9f25f89d4" When saving changes to a wiki page posting data , the POST request will contain the If-Match header containing the ETag values to check freshness against.

If-Match: "33a64dffcc55e4d42ad9f25f89d4" If the hashes don't match, it means that the document has been edited in-between and a Precondition Failed error is thrown. If a user visits a given URL again that has an ETag set , and it is stale too old to be considered usable , the client will send the value of its ETag along in an If-None-Match header field: If-None-Match: "33a64dffcc55e4d42ad9f25f89d4" The server compares the client's ETag sent with If-None-Match with the ETag for its current version of the resource, and if both values match that is, the resource has not changed , the server sends back a Not Modified status, without a body, which tells the client that the cached version of the response is still good to use fresh.

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