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

# Gas Sponsorship

> Sponsor all or part of your users' transaction fees, and handle the transactions your project does not sponsor.

Gas sponsorship lets your project cover the native gas fee on your users' transactions. You can sponsor every transaction or a configurable portion of them, and your users never need to hold a network's native token for the transactions you sponsor.

## Sponsorship configurations

By default your project sponsors everything. There is no setup step, and the gas cost is billed back to you on a monthly cycle through OMS, converted to a USD value at the time of each transaction.

You can instead sponsor a subset of transactions per user. A rule might cover a user's first three transactions, for example, and leave the rest to the user.

When a transaction is not sponsored, the user pays its fee. They do not need the network's native token to do so: preparation returns the tokens accepted for that fee, and the user can pay in a stablecoin instead.

Sponsorship is configured on your OMS project. Your application code does not select it per transaction.

## Handle both outcomes

Every transaction follows the same lifecycle:

1. Prepare the transaction.
2. Read whether the prepared transaction is sponsored, along with any fee options it returned.
3. Execute. A sponsored transaction needs no fee selection. An unsponsored transaction needs one fee option.

Because a sponsorship rule can change which outcome applies without any change to your code, handle both. Read the fee options the preparation actually returned rather than assuming a sponsored transaction never carries any.

Each SDK does this through a fee option selector. A sponsored preparation invokes your selector with an empty collection: return the platform's empty value to continue, or throw to stop execution. Every SDK also ships a `firstAvailable` selector that handles both outcomes.

| SDK                                                         | Selector                            | Continue a sponsored transaction |
| ----------------------------------------------------------- | ----------------------------------- | -------------------------------- |
| [TypeScript](/wallets/sdk/typescript/send-transactions)     | `FeeOptionSelector.firstAvailable`  | return `undefined`               |
| [React Native](/wallets/sdk/react-native/send-transactions) | `FeeOptionSelectors.firstAvailable` | return `undefined`               |
| [Swift](/wallets/sdk/swift/send-transactions)               | `.firstAvailable`                   | return `nil`                     |
| [Kotlin](/wallets/sdk/kotlin/send-transactions)             | `FeeOptionSelector.firstAvailable`  | return `null`                    |

## Transactions that are always sponsored

Three cases are sponsored regardless of your project's rules:

* **Testnets.** Transaction fees are sponsored on testnets.
* **Smart sessions.** Smart session transactions must be sponsored. OMS rejects preparation when the transaction is not sponsored, so a remote backend never selects or submits a fee option. See [Smart Sessions](/wallets/smart-sessions).
* **Server Wallet transfers.** A Server Wallet transfer requires a sponsored quote, and preparation fails without one. See [Server Wallets](/wallets/server-wallets).