Want-Digest

The HTTP Want-Digest request header asked the server to include a Digest header containing a hash of the requested resource in the response.

Note

The Want-Digest header has been deprecated. The modern digest specification supersedes the original mechanism with two replacement headers: Want-Content-Digest for content integrity and Want-Repr-Digest for representation integrity.

Table of Contents

Usage

The Want-Digest header was part of the original HTTP digest mechanism. A client included this header to ask the server to compute a hash of the response body using a specified algorithm and return the result in the Digest response header.

The primary use case was verifying data integrity after transmission. A client computed its own hash of the received body and compared the result against the value in the Digest header to confirm the content arrived without corruption.

The header used a comma-separated list of algorithm tokens, each with an optional quality value (q) indicating preference. Higher quality values signaled stronger preference. A quality value of 0 indicated the algorithm was not acceptable.

The modern digest specification replaced this mechanism with separate headers for content and representation digests. The Want-Content-Digest header requests a hash of the message content as transmitted (including any content encoding). The Want-Repr-Digest header requests a hash of the selected representation before content encoding. This separation resolves ambiguity in the original specification about which form of the data was hashed.

Values

digest-algorithm

An algorithm identifier such as sha-256 or sha-512. Multiple algorithms are separated by commas.

q (quality value)

An optional quality value between 0 and 1, separated from the algorithm by a semicolon. Higher values indicate stronger preference. A value of 0 means the algorithm is explicitly rejected.

Example

A client requesting a SHA-512 digest with a fallback to SHA-256. The quality value of 0.5 for SHA-256 indicates lower preference compared to the implicit value of 1 for SHA-512.

Want-Digest: sha-512, sha-256;q=0.5

A client explicitly requesting only SHA-256.

Want-Digest: sha-256

A server responding with the Digest header after receiving the Want-Digest request. The hash is a Base64-encoded SHA-256 digest of the response body.

Request

Want-Digest: sha-256

Response

Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=

Takeaway

The Want-Digest header requested a message digest from the server for response integrity verification. This header has been deprecated in favor of Want-Content-Digest and Want-Repr-Digest, as defined in the modern digest specification.

See also

Last updated: March 6, 2026