ETag

Table of Contents

About

The HTTP ETag (entity tag) response header is an identifier for a specific version of a resource 1. It lets caches be more efficient and save bandwidth , as a web server does not need to resend a full response if the content has not changed. Additionally, ETags help to prevent simultaneous updates of a resource from overwriting each other (“mid-air collisions”).

If the resource at a given URL changes, a new Etag value must be generated. A comparison of them can determine whether two representations of a resource are the same.

Characteristics

See Forbidden request header , HTTP Response headers , Representation headers

Header typeResponse header, Representation header
Forbidden request headerNo

Anki

References

  1. MDN. “ETag”. Available at: https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/ETag . (Accessed: [2025-05-10 Sat 05:57]). ↩︎

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