Paymaster

The Openfort Paymaster enables you to sponsor transaction fees for your users. By integrating with Openfort, you can provide seamless, gasless experiences where users don't need to hold native tokens to interact with your application.

Openfort provides fee sponsorship across both EVM chains (using the ERC-4337 Paymaster standard) and Solana (using native fee payer mechanics).

EVM (Paymaster)

For EVM-compatible chains, Openfort provides a Paymaster that implements the ERC-4337 specification. The Paymaster:

Receives a UserOperation from your application
Validates it against your sponsorship rules
Signs the operation with the paymaster's key
Returns the signature for inclusion in the UserOperation

When the UserOperation is executed on-chain, the paymaster contract verifies the signature and pays for the gas on behalf of the user.

Endpoint:

https://api.openfort.io/rpc/{chainId}

EVM Paymaster

Gas sponsorship for EVM chains

Implement the ERC-4337 Paymaster standard to sponsor gas fees for UserOperations on EVM-compatible chains.

Solana

For Solana, Openfort provides fee sponsorship using Solana's native fee payer mechanics. Solana has built-in support for fee sponsorship through "fee payers."

Fee sponsorship on Solana works by:

Receiving a transaction from your application
Validating it against your sponsorship policies
Signing the transaction as the fee payer
Returning the signed transaction for execution

Endpoint:

https://api.openfort.io/rpc/solana/{cluster}

Solana Paymaster

Fee sponsorship for Solana

Use Solana's native fee payer mechanics to sponsor transaction fees for your Solana users.

Authentication

All paymaster endpoints require authentication. Include your Openfort publishable key in the Authorization header:

Authorization: Bearer YOUR_OPENFORT_PUBLISHABLE_KEY

Get your public key from the Openfort Dashboard.

Sponsorship policies

Sponsorship policies allow you to define rules for when transactions should be sponsored. Configure policies in the Openfort Dashboard to:

Limit sponsorship to specific contract or program interactions
Set spending caps per user or time period
Restrict sponsorship to specific chains or clusters
Define custom criteria based on transaction parameters

Next steps

EVM Paymaster - Gas sponsorship for EVM chains
Solana Paymaster - Fee sponsorship for Solana