Want-Digest
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
The Want-Digest
HTTP header is primarily used in a request, to ask the server to provide a digest of the requested resource using the Digest
response header.
The header contains identifiers for one or more digest algorithms that the sender wishes the server to use to create the digest. The request may use quality values to indicate its preference/order for particular digest algorithms.
If Want-Digest
does not include any digest algorithms that the server supports, the server may respond with:
- a digest calculated using a different digest algorithm, or
- a
400 Bad Request
error, and include anotherWant-Digest
header with that response, listing the algorithms that it does support.
See the page for the Digest
header for more information.
Header type | Request header, Response header |
---|---|
Forbidden header name | no |
Syntax
http
Want-Digest: <digest-algorithm>
// Multiple algorithms, weighted with the quality value syntax:
Want-Digest: <digest-algorithm><q-value>,<digest-algorithm><q-value>
Directives
- <digest-algorithm>
-
Digest algorithms are defined in Digest Headers.
- Permitted digest algorithms values include:
unixsum
,unixcksum
,crc32c
,sha-256
andsha-512
,id-sha-256
,id-sha-512
- Deprecated algorithms values include:
md5
,sha
,adler32
.
- Permitted digest algorithms values include:
- <q-value>
-
The quality value to apply to that option.
Examples
http
Want-Digest: sha-256
Want-Digest: SHA-512;q=0.3, sha-256;q=1, md5;q=0
Basic operation
The sender provides a list of digests which it is prepared to accept, and the server uses one of them:
Request:
http
GET /item
Want-Digest: sha-256;q=0.3, sha;q=1
Response:
http
HTTP/1.1 200 Ok
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
Unsupported digests
The server does not support any of the requested digest algorithms, so uses a different algorithm:
Request:
http
GET /item
Want-Digest: sha;q=1
Response:
http
HTTP/1.1 200 Ok
Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
The server does not support any of the requested digest algorithms.
In this case it responds with a 400 error and includes another Want-Digest
header, listing the algorithms that it does support:
Request:
http
GET /item
Want-Digest: sha;q=1
Response:
http
HTTP/1.1 400 Bad Request
Want-Digest: sha-256, sha-512
Specifications
Specification |
---|
Digest Fields # section-4 |
Browser compatibility
BCD tables only load in the browser