OAuth exists to let three separate parties (user → platform → third-party app) establish mutual trust. Farcaster is built on a decentralized architecture that collapses this triangle:

## 1. Identity & Authentication

- **User-owned keys:** A user controlled cryptographic signature proves control of a Farcaster ID—no intermediary.
- **Dev mappings**  
  - Sign In with X → Sign-in with Farcaster (SIWF)  
  - OAuth 2.0 Authorization Flow → Quick Auth

## 2. Data Access & Permissions

- **Open, replicated data:** Social data like casts, reactions, and profiles live on Snapchain and can be read by anyone.
- **No permission scopes:** Everything is already public; you filter what you need instead of requesting scopes.
- **Zero-cost reads:** Sync the chain yourself or hit a public indexer—no rate caps, no $5k +/month fire-hoses.
- **Cryptographic writes:** Users can delegate a key to applications so the applications can write on their behalf.
- **Dev mappings**  
  - Centralized APIs → Snapchain + infra services (e.g. Neynar)  
  - Access token → no equivalent, data is public  
  - Write permissions → App Keys

## Builder Takeaways

1. **Skip OAuth flows—wallet signature = auth.**
2. **Forget permission scopes—use filters.**
3. **Enjoy building permissionlessly**

## Resources

- [Quick Auth](https://docs.neynar.com/miniapps/sdk/quick-auth)
- [Neynar SDK for one-call Snapchain queries](https://docs.neynar.com/reference/quickstart)
- [App Keys](https://docs.farcaster.xyz/reference/warpcast/signer-requests)