Usernames & proofs #

Farcaster usernames are backed by off-chain "fnames" and on-chain ENS/Basenames. These endpoints let you check availability and look up the proof record attached to a name.

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GET /v2/farcaster/fname/availability #

Is an fname available to register?

Query parameters

Name	Type	Required
fname	string	yes

Response

{
  "available": true,
  "username": null
}

If the name is taken, available is false and username contains the normalized name string.

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GET /v2/farcaster/username-proof #

Fetch the raw username proof record for a given name. Useful when you want to verify on-chain provenance yourself instead of trusting the resolved User.username field.

Query parameters

Name	Type	Required
username	string	yes

Response

{
  "username_proof": {
    "timestamp": 1712345678,
    "name": "alice",
    "owner": "0x...",
    "signature": "0x...",
    "fid": 12345,
    "type": "USERNAME_TYPE_FNAME"
  }
}

If the name has no proof, username_proof is null.