Farcaster is a decentralized social protocol where accounts, keys, and storage limits live on-chain, while posts and social actions sync through a public node network (Hubs → now “Snapchain”). Apps like Warpcast provide the mainstream UI, and developers can build their own clients, bots, and Mini Apps (formerly “Frames v2”) that run inside the feed.
Quick Facts
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Product: Farcaster (social protocol) • Founded: 2020 • Founders: Dan Romero, Varun Srinivasan.
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Core contracts (on-chain): Id Registry, Key Registry, Storage Registry on Optimism; Tier Registry (Farcaster Pro) on Base.
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Identity: Users get a permanent FID; usernames can be off-chain fnames (free, revocable) or on-chain ENS names (non-revocable).
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Data layer: Posts/reactions/links sync via Hubs/Snapchain; Snapchain introduces ordered blocks and state pruning for scale.
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In-feed apps: Mini Apps (rebranded from Frames v2 in early 2025) power interactive experiences directly in the feed.
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Clients & APIs: Official Farcaster Client API (channels, DMs, etc.), Snapchain gRPC/HTTP for protocol data, Neynar hosted hubs & SDKs.
Key Features
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On-chain accounts & delegated keys: Create an FID, then add Ed25519 “signer” keys so apps can post on your behalf (without custody of your wallet).
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Storage-rent model (no per-post gas): Rent storage units (1-year terms) via the Storage Registry; units cap rate/volume and keep spam in check.
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Snapchain nodes (formerly Hubs): Public nodes sync social data; Snapchain adds block ordering for stronger consistency vs. prior gossip-only hubs.
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Channels & discovery: Topic feeds (“channels”) with public casting, membership, and stats exposed via the client API.
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Direct Casts (DMs): Available via the official client’s API; not yet part of the core protocol.
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Mini Apps (in-feed apps): Ship interactive apps with auth, notifications, and wallet actions—no app-store review.
How It Works (at a glance)
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Register an account (FID): Call the Id Registry (Optimism) or use an onboarding flow (e.g., Neynar).
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Add signer keys: Your app creates an Ed25519 keypair and requests the user’s approval; the key is approved on-chain via the Signed Key Request flow.
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Rent storage: Buy storage units via the Storage Registry; messages count toward your per-unit limits for a year.
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Publish & sync: Clients post messages to nodes; Snapchain orders them into blocks and prunes old state per rules.
Mini Apps (formerly Frames)
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Status: Frames v2 → Mini Apps (rename + migration; Frames v2 support ended March 2025).
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Why Mini Apps: 1-click discovery in the feed, auth via Farcaster identity, notifications, and integrated Ethereum/Solana wallet actions.
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Builder docs: miniapps.farcaster.xyz (guides, SDK, auth/notifications, wallet actions).
Clients & Ecosystem
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Warpcast is the most popular client (channels, DMs, Mini Apps, discovery).
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Developer platforms: Neynar (hosted hubs, REST, signer mgmt, webhooks), data mirrors on Dune.
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Community lists: “Awesome Farcaster” catalogs alternative clients, SDKs, and services
Developer & API Surface
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Protocol data: Snapchain gRPC/HTTP: casts, reactions, links, usernames, storage, events, sync.
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Official client API: Channels, DMs, channel membership, and more (host: api.farcaster.xyz).
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Auth: AuthKit (Sign-in with Farcaster) – React hooks/components and relay server.
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Third-party SDKs: Neynar APIs/SDKs for read/write, signer flows, and Mini App auth.
