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This guide covers how to use the Swig Paymaster SDK to sponsor transaction fees for your users, enabling gasless transactions.

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What is a Paymaster?

A paymaster is a service that pays transaction fees on behalf of users. Instead of requiring users to hold SOL for gas fees, the paymaster covers these costs, creating a seamless onboarding experience. Benefits:
  • Users don’t need SOL for transaction fees
  • Lower barrier to entry for new users
  • Better user experience for dApps

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Prerequisites

Before using the paymaster SDK:
  1. Create a paymaster in the Developer Portal
  2. Fund your paymaster with SOL
  3. Get your API key from the Developer Portal
Paymasters require a paid subscription (PRO, ULTRA, or ENTERPRISE). See Subscriptions & Billing for details.

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Installation

Choose the package that matches your Solana SDK version: 
npm install @swig-wallet/paymaster-classic
For applications using @solana/web3.js version 1.x (the traditional Solana SDK).

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Configuration

Create a paymaster client with your credentials: 
import { createPaymasterClient } from '@swig-wallet/paymaster-classic';

const paymaster = createPaymasterClient({
  apiKey: process.env.SWIG_API_KEY!,
  paymasterPubkey: process.env.PAYMASTER_PUBKEY!,
  baseUrl: 'https://api.onswig.com',
  network: 'devnet',
});

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Configuration Options

OptionTypeRequiredDescription
apiKeystringYesAPI key from Developer Portal
paymasterPubkeystringYesPaymaster public key
baseUrlstringYesPaymaster API URL (https://api.onswig.com)
network'mainnet' | 'devnet'YesSolana network
customRpcUrlstringNoCustom RPC endpoint (overrides default)
retryOptionsobjectNoRetry configuration for failed requests

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Retry Options

Configure automatic retries for transient failures: 
const paymaster = createPaymasterClient({
  apiKey: 'sk_your_api_key',
  paymasterPubkey: '...',
  baseUrl: 'https://api.onswig.com',
  network: 'mainnet',
  retryOptions: {
    maxRetries: 3,        // Number of retry attempts
    retryDelay: 1000,     // Initial delay in milliseconds
    backoffMultiplier: 2, // Exponential backoff multiplier
  },
});

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Quick Start

Here’s a minimal example to sponsor a transaction: 
import { Keypair, PublicKey, TransactionInstruction } from '@solana/web3.js';
import { createPaymasterClient } from '@swig-wallet/paymaster-classic';

// Initialize client
const paymaster = createPaymasterClient({
  apiKey: process.env.SWIG_API_KEY!,
  paymasterPubkey: process.env.PAYMASTER_PUBKEY!,
  baseUrl: 'https://api.onswig.com',
  network: 'devnet',
});

// User's keypair
const userKeypair = Keypair.generate();

// Create an instruction (memo example)
const instruction = new TransactionInstruction({
  keys: [{ pubkey: userKeypair.publicKey, isSigner: true, isWritable: false }],
  programId: new PublicKey('MemoSq4gqABAXKb96qnH8TysNcWxMyWCqXgDLGmfcHr'),
  data: Buffer.from('Hello, gasless world!'),
});

// Create transaction - paymaster is set as fee payer
const transaction = await paymaster.createLegacyTransaction(
  [instruction],
  [userKeypair], // User signs here
);

// Paymaster signs and sends
const signature = await paymaster.signAndSend(transaction);
console.log(`https://explorer.solana.com/tx/${signature}?cluster=devnet`);

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Transaction Flow

The paymaster transaction flow works as follows: 
┌─────────────┐    ┌─────────────┐    ┌─────────────┐    ┌─────────────┐
│   Create    │───▶│    User     │───▶│  Paymaster  │───▶│   Submit    │
│ Transaction │    │    Signs    │    │    Signs    │    │  to Network │
└─────────────┘    └─────────────┘    └─────────────┘    └─────────────┘
       │                  │                  │                  │
       ▼                  ▼                  ▼                  ▼
   Paymaster         User proves       Fee covered        Transaction
   as fee payer     authorization      by paymaster        confirmed
  1. Create Transaction: Build the transaction with the paymaster set as the fee payer
  2. User Signs: User signs to authorize the transaction
  3. Paymaster Signs: Paymaster validates and signs (covering the fee)
  4. Submit: Transaction is sent to the Solana network

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Next Steps