HTTP ETag
The ETag or entity tag is part of HTTP, the protocol for the World Wide Web.
Web cache validation
The ETag is one of several mechanisms that HTTP provides for web cache validation, which allows a client (computing) to make conditional requests.
This allows caches to be more efficient, and saves bandwidth, as a web server does not need to send a full response if the content has not changed.
ETags can also be used for optimistic concurrency control, as a way to help prevent simultaneous updates of a resource from overwriting each other.
Opaque identifier
An ETag is an opaque identifier assigned by a web server to a specific version of a resource found at a URL.
If the resource representation at that URL ever changes, a new and different ETag is assigned.
Used in this manner, ETags are similar to fingerprints, and they can be quickly compared to determine whether two representations of a resource are the same.
See also
External links
- HTTP ETag @ Wikipedia
