What does OAuth 1.0 realm stand for?

Question

The OPTIONAL realm parameter is added and interpreted per [RFC2617], section 1.2. [OAuth 1.0]

What is the difference between a request with and without a realm field?

Answer 1

The Provider basically decides if this is of any importance. It is the counterpart of the WWW-authenticate response header. If a sever returns a WWW-authenticate header of 'OAuth realm="https://api.example.com"' then it probably parses that value from the Authenticate request header in the OAuth process.

These headers have a more direct implication when using HTTP-basic authentication since all browsers support this.

When using OAuth and WWW-authenticate header it is mostly good form I would say. With the added benefit of not having API responses cached in proxies/nodes across the Internet.