Learn · Building on Flare

The Data Connector (FDC)

The Flare Data Connector (FDC) lets contracts trust external and cross-chain facts. Providers attest the data by consensus; you receive a Merkle proof your contract can verify.

Attestation types

• EVMTransaction — confirm a transaction and read its events on another EVM chain.
• Web2Json — fetch a Web2 API, apply a JQ transform, return ABI-encoded output.
• Payment / AddressValidity — confirm payments / validate addresses on BTC, DOGE, XRPL.
• ConfirmedBlockHeightExists, ReferencedPaymentNonexistence, … — building blocks for FAssets.

The request → proof flow

1. Prepare the request via a Verifier API (it returns the ABI-encoded request).
2. Submit it to FdcHub.requestAttestation() with the fee.
3. Wait for the voting round to finalize (~90–180s).
4. Fetch the Merkle proof from the DA Layer for that round.
5. Verify on-chain with IFdcVerification.verify…(), then use the decoded data.

Only the Merkle root lives on-chain; the full attestation set stays in the Data Availability Layer, so verification is cheap. Use cases: cross-chain settlement, proof-of-reserves, parametric insurance, RWA data.

Last reviewed June 2026