Best HTTP Authorization header type for JWT

The best HTTP header for your client to send an access token (JWT or any other token) is the Authorization header with the Bearer authentication scheme.

This scheme is described by the RFC6750.

Example:

GET /resource HTTP/1.1
Host: server.example.com
Authorization: Bearer eyJhbGciOiJIUzI1NiIXVCJ9TJV...r7E20RMHrHDcEfxjoYZgeFONFh7HgQ

If you need stronger security protection, you may also consider the following IETF draft: https://datatracker.ietf.org/doc/html/draft-ietf-oauth-pop-architecture. This draft seems to be a good alternative to the (abandoned?) https://datatracker.ietf.org/doc/html/draft-ietf-oauth-v2-http-mac.

Note that even if this RFC and the above specifications are related to the OAuth2 Framework protocol, they can be used in any other contexts that require a token exchange between a client and a server.

Unlike the custom JWT scheme you mention in your question, the Bearer one is registered at the IANA.

Concerning the Basic and Digest authentication schemes, they are dedicated to authentication using a username and a secret (see RFC7616 and RFC7617) so not applicable in that context.

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Short answer

The Bearer authentication scheme is what you are looking for.

Long answer

Is it related to bears?

Errr... No :)

According to the Oxford Dictionaries, here's the definition of bearer:

bearer /ˈbɛːrə/ noun A person or thing that carries or holds something. A person who presents a cheque or other order to pay money.

The first definition includes the following synonyms: messenger, agent, conveyor, emissary, carrier, provider.

And here's the definition of bearer token according to the RFC 6750:

1.2. Terminology Bearer Token A security token with the property that any party in possession of the token (a "bearer") can use the token in any way that any other party in possession of it can. Using a bearer token does not require a bearer to prove possession of cryptographic key material (proof-of-possession).

The Bearer authentication scheme is registered in IANA and originally defined in the RFC 6750 for the OAuth 2.0 authorization framework, but nothing stops you from using the Bearer scheme for access tokens in applications that don't use OAuth 2.0.

Stick to the standards as much as you can and don't create your own authentication schemes.

An access token must be sent in the Authorization request header using the Bearer authentication scheme:

2.1. Authorization Request Header Field When sending the access token in the Authorization request header field defined by HTTP/1.1, the client uses the Bearer authentication scheme to transmit the access token. For example: GET /resource HTTP/1.1 Host: server.example.com Authorization: Bearer mF_9.B5f-4.1JqM [...] Clients SHOULD make authenticated requests with a bearer token using the Authorization request header field with the Bearer HTTP authorization scheme. [...]

In case of invalid or missing token, the Bearer scheme should be included in the WWW-Authenticate response header:

3. The WWW-Authenticate Response Header Field If the protected resource request does not include authentication credentials or does not contain an access token that enables access to the protected resource, the resource server MUST include the HTTP WWW-Authenticate response header field [...]. All challenges defined by this specification MUST use the auth-scheme value Bearer. This scheme MUST be followed by one or more auth-param values. [...]. For example, in response to a protected resource request without authentication: HTTP/1.1 401 Unauthorized WWW-Authenticate: Bearer realm="example" And in response to a protected resource request with an authentication attempt using an expired access token: HTTP/1.1 401 Unauthorized WWW-Authenticate: Bearer realm="example", error="invalid_token", error_description="The access token expired"

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