# Sponsor User Fees

## Overview

A **fee payer** can cover the gas fees for a transaction on behalf of the sender, enabling a
gasless experience for your users. The sender signs the transaction, and the fee payer
separately authorizes paying its fees via the `feePayer` property.

You can sponsor fees with a local account, or delegate to a remote relay service so the fee
payer's key never leaves your server.

[See the Sponsor User Fees guide](https://docs.tempo.xyz/guide/payments/sponsor-user-fees)

## Recipes

These recipes assume you have [set up a Tempo client](/tempo).

### Sponsor with a Local Account

Pass a local account as `feePayer` to [`sendTransactionSync`](/docs/actions/wallet/sendTransactionSync).
The sender signs the transaction and the fee payer signs to cover its fees.

:::code-group
```ts twoslash [example.ts]
import { Account } from 'viem/tempo'
import { client } from './viem.config'

const feePayer = Account.fromSecp256k1('0x...') // [!code focus]

const receipt = await client.sendTransactionSync({
  data: '0xdeadbeef',
  feePayer, // [!code focus]
  to: '0xcafebabecafebabecafebabecafebabecafebabe',
})
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
// [!include ~/snippets/tempo/viem.config.ts:setup]
```
:::

### Sponsor via a Relay

To keep the fee payer's key server-side, route requests through a relay with the
[`withRelay`](/tempo/transports/withRelay) transport, then set `feePayer: true` to ask the
relay to sponsor the transaction.

```ts twoslash
import { Account, createClient, http, withRelay } from 'viem/tempo'

const client = createClient({
  account: Account.fromSecp256k1('0x...'),
  testnet: true,
  transport: withRelay( // [!code focus]
    http(), // default transport // [!code focus]
    http('https://relay.example.com'), // relay transport // [!code focus]
  ), // [!code focus]
})

const receipt = await client.sendTransactionSync({
  data: '0xdeadbeef',
  feePayer: true, // [!code focus]
  to: '0xcafebabecafebabecafebabecafebabecafebabe',
})
```

:::info
For setting up the relay service itself, see the
[Sponsor User Fees guide](https://docs.tempo.xyz/guide/payments/sponsor-user-fees) in the Tempo
docs.
:::

## Best Practices

### Choose Local vs Relay

* **Local account**: simplest to set up, but the fee payer's private key lives in the same
  process as the sender. Best for scripts, backends, and testing.
* **Relay**: the fee payer's key stays on your server behind the relay endpoint, and clients
  only send `feePayer: true`. Best for production apps sponsoring fees for many users.

### Combine with a Fee Token

Sponsorship and stablecoin fees compose: the fee payer can settle the sponsored fees in a
`feeToken`. See [Pay Fees in a Stablecoin](/tempo/guides/pay-fees).

## See More

<Cards>
  <Card icon="lucide:coins" title="Pay Fees in a Stablecoin" description="Pay transaction fees in any USD-denominated TIP-20 stablecoin token." to="/tempo/guides/pay-fees" />

  <Card icon="lucide:square-function" title="withRelay" description="Route relay traffic so a server-side fee payer can sponsor transactions." to="/tempo/transports/withRelay" />

  <Card icon="lucide:book-open" title="Tempo Docs: Sponsor User Fees" description="The full guide to fee sponsorship and running a fee payer relay." to="https://docs.tempo.xyz/guide/payments/sponsor-user-fees" />
</Cards>