S256

The "S256" code challenge method, which applies SHA-256 hashing to the code verifier. This must be supported by all clients and Authorization Servers; see RFC 7636 for details.

The transform involves a relatively simple SHA-256 hash and base64url string encoding. The code value is a set of 32 to 96 random bytes, encoded in base64url (resulting in 43 or more string-encoded characters).