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

# Paymaster

> How to use Particle Network’s Omnichain Paymaster for cross-chain gas sponsorship.

# Particle Omnichain Paymaster

The **Omnichain Paymaster** lets you sponsor gas fees across multiple chains with a **single USDT deposit**.

* Deposit USDT once (Ethereum or BNB Chain)
* Funds are automatically converted into the native gas token of the target chain
* Works out of the box with Particle’s Smart Wallet-as-a-Service
* Free to use on testnets (no deposit required)
* Fully customizable sponsorship logic via webhooks

This removes the need to manage separate balances for each chain.

***

## How to Use the Paymaster

There are two ways to use the Paymaster:

### 1. Through Particle’s AA SDKs

* Enabled automatically, no setup required.
* On testnets, transactions are sponsored for free.
* On mainnets, sponsorship is funded from your project’s Paymaster balance.

👉 Quickstarts: [Web](/aa/quickstart/web-aa) • [Mobile](/aa/quickstart/mobile-aa)

### 2. Through the Paymaster RPC

If you want direct control:

[https://paymaster.particle.network](https://paymaster.particle.network)

Supported RPC methods:

* `pm_sponsorUserOperation` — request gas sponsorship
* `pm_paymasterBalance` — check your deposit balance

👉 See [Paymaster RPC](/aa/paymaster/paymasterbalance) for examples and parameters.

***

## Funding the Paymaster

To sponsor transactions on mainnets:

1. Go to the [Particle Dashboard](https://dashboard.particle.network).
2. Create a project (if you don’t have one yet).
3. Open the **Paymaster** menu.
4. Deposit USDT on **Ethereum** or **BNB Chain**.

* Deposits are tied to your project (`projectId`, `clientKey`, `appId`).
* Deposits automatically cover sponsorships across all supported EVM chains.

<Note>USDT is not required for testnet sponsorship.</Note>

<div className="flex justify-center">
  <img className="block h-64 dark:hidden" src="https://mintcdn.com/particlenetwork-fccf74d2/QUNIZtuxVpfIWkQc/aa/images/paymaster.png?fit=max&auto=format&n=QUNIZtuxVpfIWkQc&q=85&s=78fb233072a820f53b05a5b958392103" alt="Paymaster menu." width="1512" height="1031" data-path="aa/images/paymaster.png" />

  <img className="hidden h-64 dark:block" src="https://mintcdn.com/particlenetwork-fccf74d2/QUNIZtuxVpfIWkQc/aa/images/paymaster.png?fit=max&auto=format&n=QUNIZtuxVpfIWkQc&q=85&s=78fb233072a820f53b05a5b958392103" alt="Paymaster menu." width="1512" height="1031" data-path="aa/images/paymaster.png" />
</div>

***

## Conditional Sponsorship (Webhooks)

You can define rules for when sponsorship applies using **webhooks**.

Available hooks:

* `before_paymaster_sign` — runs before sponsorship; determines if the `UserOp` should be signed.
* `after_paymaster_sign` — runs after sponsorship; useful for logging or post-processing.

Both hooks receive:

* `projectUuid` — your project ID
* `chainId` — chain where sponsorship is requested
* `userOp` — the full `UserOperation` object
* `entryPoint` — standard EntryPoint address (`0x5FF137...`)
* `parsed` — simplified transaction array

Return `200` to confirm sponsorship, or `400` to reject.

### Example: `before_paymaster_sign`

```json json [expandable] theme={null}
POST https://your-domain/hook-before-paymaster-sign
{
  "type": "before_paymaster_sign",
  "chainId": 80001,
  "projectUuid": "ef6c29f5-ad2b-545c-ad0c-54441068b71d",
  "userOp": {
        "sender": "0x2e9661BDA6201F97430dcc1541A1579b83980DD1",
        "nonce": "0x05",
        "initCode": "0x",
        "callData": "0xb61d27f6000000000000000000000000ac6a87c681a5ed4cb58bc4fa7bf81a83b928c83c00000000000000000000000000000000000000000000000000005af3107a400000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000",
        "callGasLimit": "0x9acc",
        "verificationGasLimit": "0x0186a0",
        "preVerificationGas": "0xc5dc",
        "maxFeePerGas": "0xa79dd02a",
        "maxPriorityFeePerGas": "0xa79dd015",
        "paymasterAndData": "0x",
        "signature": "0x"
        },
  "parsed": {
    "accountType": "SIMPLE",
    "txs": [
      { "to": "0xaC6A...", "value": "0x5af3107a4000", "data": "0x" }
    ]
  }
}
```

### Example: `after_paymaster_sign`

```json json [expandable] theme={null}
POST https://your-domain/hook-after-paymaster-sign
{
  "type": "after_paymaster_sign",
  "chainId": 80001,
  "projectUuid": "ef6c29f5-ad2b-545c-ad0c-54441068b71d",
  "userOpHash": "0x45d4f...",
  "userOp": { "sender": "0x...", "nonce": "0x05", ... }
}
```

### Request Verification

All webhook requests from Particle are signed.

* A unique RSA-2048 keypair is generated for each project.
* Download your project’s public key from the Particle Dashboard.
* Use it to verify the `x-particle-signature` header on incoming requests.

<div className="flex justify-center">
  <img className="block h-64 dark:hidden" src="https://mintcdn.com/particlenetwork-fccf74d2/QUNIZtuxVpfIWkQc/aa/images/validate.png?fit=max&auto=format&n=QUNIZtuxVpfIWkQc&q=85&s=635a21472387cc62db5d2e0f250cf5b1" alt="Request verification." width="505" height="398" data-path="aa/images/validate.png" />

  <img className="hidden h-64 dark:block" src="https://mintcdn.com/particlenetwork-fccf74d2/QUNIZtuxVpfIWkQc/aa/images/validate.png?fit=max&auto=format&n=QUNIZtuxVpfIWkQc&q=85&s=635a21472387cc62db5d2e0f250cf5b1" alt="Request verification." width="505" height="398" data-path="aa/images/validate.png" />
</div>

### Additional Resources

<CardGroup cols={2}>
  <Card title="Paymaster RPC Reference" icon="code" href="/aa/paymaster/paymasterbalance" />

  <Card title="Architecture Overview" icon="diagram-project" href="/aa/architecture/omni-paymaster" />
</CardGroup>