> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# CCTP API hosts and endpoints V1

> API hosts and endpoints for CCTP V1

<Warning>
  **This is CCTP V1 version. For the latest version, see [CCTP](/cctp)**.
</Warning>

CCTP V1 provides a set of API hosts and endpoints to manage messages,
attestations, and transaction details for your cross-chain USDC transfers.

## CCTP V1 API Service Hosts

| Environment | URL                                   |
| :---------- | :------------------------------------ |
| **Testnet** | `https://iris-api-sandbox.circle.com` |
| **Mainnet** | `https://iris-api.circle.com`         |

## CCTP V1 API Endpoints

CCTP V1 endpoints allow you to fetch attestations for **Standard Transfer** burn
events, verify public keys, and access transaction details. Below is an overview
of the CCTP V1 public endpoints. Click on any endpoint for its API reference.

| Endpoint                                                                                      | Description                                                                 | Use Case                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| --------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`GET /v1/attestations/{messageHash}`](/api-reference/cctp/all/get-attestation)               | Retrieves the signed attestation for a USDC burn event on the source chain. | Certifying the burn of USDC post <Tooltip tip="The point at which a transaction is fully finalized on-chain and can no longer be reversed or reorganized. This ensures the highest level of security and certainty before attestation. Hard Finality requires the transaction to reach full consensus on the source blockchain, typically resulting in longer processing times.">hard finality</Tooltip>. Used as a signal to mint USDC on the destination chain. |
| [`GET /v1/publicKeys`](/api-reference/cctp/all/get-public-keys)                               | Fetches Circle's active public keys for verifying attestation signatures.   | Validating the authenticity of Circle's signed attestations.                                                                                                                                                                                                                                                                                                                                                                                                      |
| [`GET /v1/messages/{sourceDomainId}/{transactionHash}`](/api-reference/cctp/all/get-messages) | Provides transaction details for burn events or associated messages.        | Accessing detailed information about CCTP V1 transactions.                                                                                                                                                                                                                                                                                                                                                                                                        |

<Note>
  **API Service Rate Limit**

  The CCTP V1 API service rate limit is 35 requests per second. If you exceed 35
  requests per second, the service blocks all API requests for the next 5 minutes
  and returns an HTTP 429 response.
</Note>