What’s an ETag?

[chinmay.sahoo]

Entity tags (ETags) are a mechanism that web servers and browsers use to validate cached components.Before jumping into the details of ETags, let's review how components are cached and validated.

[RH-Calvin]

Quiet interesting! An ETag is an opaque identifier assigned by a web server to a specific version of a resource found at a URL. It is one of several mechanisms that HTTP provides for web cache validation, and which allows a client 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,[1] as a way to help prevent simultaneous updates of a resource from overwriting each other.