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

# Relayer Overview

> JSON-RPC methods for gasless and sponsored transactions

The Gelato Relayer provides a standardized set of JSON-RPC methods for submitting gasless transactions. These methods support sponsored transactions and transaction status tracking.

## Base URL

```
https://api.gelato.cloud/rpc
```

## Available Methods

### Transaction Submission

| Method                                                                                                         | Description                                  |
| -------------------------------------------------------------------------------------------------------------- | -------------------------------------------- |
| [`relayer_sendTransaction`](/gasless-with-relay/relayer-api-endpoints/relayer/relayer_sendtransaction)         | Submit a signed transaction for relay        |
| [`relayer_sendTransactionSync`](/gasless-with-relay/relayer-api-endpoints/relayer/relayer_sendtransactionsync) | Submit and wait for transaction confirmation |

### Fee Estimation

| Method                                                                                                 | Description                                              |
| ------------------------------------------------------------------------------------------------------ | -------------------------------------------------------- |
| [`relayer_getCapabilities`](/gasless-with-relay/relayer-api-endpoints/relayer/relayer_getcapabilities) | Get supported payment tokens and fee collector addresses |
| [`relayer_getFeeData`](/gasless-with-relay/relayer-api-endpoints/relayer/relayer_getfeedata)           | Get token exchange rates for manual fee calculation      |
| [`relayer_getFeeQuote`](/gasless-with-relay/relayer-api-endpoints/relayer/relayer_getfeequote)         | Get a fee quote for a specific gas amount                |

### Status Tracking

| Method                                                                                     | Description                                |
| ------------------------------------------------------------------------------------------ | ------------------------------------------ |
| [`relayer_getStatus`](/gasless-with-relay/relayer-api-endpoints/relayer/relayer_getstatus) | Check status with full transaction receipt |

## Payment Type

### Sponsored

The relayer covers gas fees. Requires a valid API key with sufficient Gas Tank balance.

```json theme={null}
{
  "payment": {
    "type": "sponsored"
  }
}
```

## Authentication

All requests require an API key passed via the `X-API-Key` header:

```bash theme={null}
curl -X POST https://api.gelato.cloud/rpc \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -d '{ ... }'
```

Create an API Key at the [Gelato App](https://app.gelato.cloud/).

## Status Codes

| Code  | Status    | Description                               |
| ----- | --------- | ----------------------------------------- |
| `100` | Pending   | Transaction received, not yet submitted   |
| `110` | Submitted | Transaction broadcast, awaiting inclusion |
| `200` | Included  | Transaction confirmed on-chain            |
| `400` | Rejected  | Transaction rejected by relayer           |
| `500` | Reverted  | Transaction reverted on-chain             |

## Error Codes

| Code     | Message                   | Description                     |
| -------- | ------------------------- | ------------------------------- |
| `-32602` | Invalid params            | Missing or malformed parameters |
| `4100`   | Unauthorized              | Invalid or missing API key      |
| `4200`   | Insufficient Payment      | Payment amount too low          |
| `4201`   | Invalid Signature         | Signature verification failed   |
| `4202`   | Unsupported Payment Token | Token not supported             |
| `4204`   | Quote Expired             | Fee quote has expired           |
| `4205`   | Insufficient Balance      | User balance too low            |
| `4206`   | Unsupported Chain         | Chain ID not supported          |
| `4208`   | Unknown Transaction ID    | Task ID not found               |
| `4211`   | Simulation Failed         | Transaction simulation failed   |