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Response

ETag

Provides a unique identifier for a specific version of a resource, enabling efficient conditional requests.

Syntax

ETag: "<etag_value>" | W/"<etag_value>"

Example

ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4"

Description

ETag (Entity Tag) provides a unique identifier for a resource version. Browsers send it back via If-None-Match for 304 Not Modified responses.

Can be strong (exact match) or weak (prefixed with W/). Strong ETags required for byte-range requests.

More precise than Last-Modified. Most servers generate ETags automatically.

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Related Headers

Connection
Controls whether the network connection stays open after the current transaction finishes.
Content-Disposition
Indicates whether the response should be displayed inline or downloaded as a file attachment.
Content-Encoding
Specifies the compression algorithm applied to the response body, such as gzip or brotli.
Content-Length
Specifies the size of the response body in bytes.
Content-Type
Indicates the media type of the response body, telling the browser how to interpret and display the content.
Date
Indicates the date and time at which the response was generated by the server.

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