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Farcaster implements three contracts on the Goerli Ethereum testnet to manage identities:


The source code can be viewed here. On testnet, registration is managed by a single address controlled by the Farcaster team. Registration will be open to everyone when the contracts launch on mainnet.

Id Registry

The ID Registry contract issues Farcaster IDs or fids to users.

An fid is a number like 234324 which is owned by an Ethereum address. An address can only own a single fid at a time, but fids can be transferred between addresses. The address that currently owns an fid is known as the custody address and can sign messages on behalf of the fid.

Ownership of fids is fully decentralized and they never expire. The contract is non-upgradeable and there are no admin functions to revoke fids once issues.

Name Registry

The Name Registry contract issues Farcaster names or fnames to users.

An fname is a username like alice which is owned by an Ethereum address. They are ERC-721 tokens that can be transferred between addresses. Fnames can be up to 16 characters including lowercase letters, numbers and hyphens. Fnames can be registered for one year at a time and must be renewed by paying a fee.

Fnames are optional, cosmetic identifiers for the Farcaster network to make fids easily addressable. Ownership is not fully decentralized and they are subject to a username policy.

Bundle Registry

The Bundle Registry is a contract that allows registering an fid an fname in a single transaction to lower gas fees. It is a convenience contract that is designed for use on testnet where registration is managed by the Farcaster team.