Crypto Gloss

Pimlico

Definition:

Pimlico is the leading ERC-4337 Account Abstraction infrastructure provider offering production-grade Bundler APIs (for submitting UserOperations and getting bundle inclusion), Paymaster APIs (for gas sponsorship and ERC-20 fee payments), and permissionless infrastructure tooling — making it the most commonly referenced backend for wallet and DApp developers implementing smart contract wallets, gasless UX, and one-click onboarding flows on EVM chains. Pimlico is the primary infrastructure choice in ERC-4337 tutorials and the permissionless.js library documentation.

Core Products

Bundler API:

Pimlico operates ERC-4337 Bundlers on 30+ chains, accessible via JSON-RPC:

“`

https://api.pimlico.io/v2/{chainId}/rpc?apikey={API_KEY}

“`

Standard ERC-4337 Bundler methods:

  • eth_sendUserOperation — submit a UserOperation to the Bundler’s mempool
  • eth_getUserOperationByHash — check status of a UserOperation
  • eth_getUserOperationReceipt — get inclusion receipt once mined
  • eth_estimateUserOperationGas — estimate gas for a UserOperation

Pimlico’s Bundler offers a free tier (no API key required for low volume) — making it the default infrastructure for development and prototyping.

Paymaster API:

Pimlico operates two types of Paymasters:

Sponsorship Paymaster:

Covers gas fees entirely for users. DApp developers pre-fund the Paymaster and configure rules (which smart wallets to sponsor, up to what USD limit, etc.):

“`typescript

const paymasterClient = createPimlicoPaymasterClient({

transport: http(https://api.pimlico.io/v2/${chain}/rpc?apikey=...),

entryPoint: ENTRYPOINT_ADDRESS_V07,

});

const sponsorUserOperationResult = await paymasterClient.sponsorUserOperation({

userOperation: unsignedUserOp,

});

“`

ERC-20 Paymaster:

Allows users to pay gas fees in ERC-20 tokens (USDC, DAI, etc.) instead of ETH:

  • User approves the Paymaster to spend their ERC-20
  • Paymaster fronts the ETH gas cost on behalf of the user
  • Paymaster deducts the equivalent ERC-20 amount from the user

This eliminates the “I need ETH for gas to move my USDC” problem — a major onboarding friction point.

Alto Bundler

Pimlico’s open-source Bundler implementation is called Alto:

  • Written in TypeScript
  • MIT licensed
  • The most-starred open-source ERC-4337 bundler implementation on GitHub
  • Developers can self-host Alto for full control over bundling

“`bash

git clone https://github.com/pimlicolabs/alto

cd alto && npm install

npx alto –config alto.config.ts

“`

permissionless.js

Pimlico co-maintains permissionless.js — a TypeScript library for building ERC-4337 applications:

  • Built on top of viem (Ethereum TypeScript library)
  • Abstracts over Bundler and Paymaster interactions
  • Supports multiple smart account implementations (SimpleAccount, SafeAccount, etc.)

“`typescript

import { createSmartAccountClient } from “permissionless”;

import { signerToSimpleSmartAccount } from “permissionless/accounts”;

const smartAccount = await signerToSimpleSmartAccount(publicClient, {

signer: owner,

entryPoint: ENTRY_POINT_ADDRESS,

});

const smartAccountClient = createSmartAccountClient({

account: smartAccount,

bundlerTransport: http(pimlicoEndpoint),

middleware: { sponsorUserOperation: paymasterClient.sponsorUserOperation },

});

// Send a gasless transaction

const txHash = await smartAccountClient.sendTransaction({

to: “0xRecipient”,

value: parseEther(“0.01”),

});

“`

Supported Chains

Pimlico supports ERC-4337 bundling and paymaster services on 30+ chains:

  • Ethereum, Arbitrum, Optimism, Base, Polygon
  • zkSync Era, Linea, Scroll, Mantle
  • Testnets for all major chains

Comparison to Other ERC-4337 Providers

Feature Pimlico Alchemy Account Kit Biconomy Stackup
Open-source bundler Yes (Alto) Partial No Yes
Free tier Yes (generous) Yes Yes Yes
ERC-20 paymaster Yes Yes Yes Yes
TypeScript SDK permissionless.js Account Kit Biconomy SDK userop.js
Primary focus Infrastructure Full-stack wallet Full-stack wallet Infrastructure

Use in the Ecosystem

Pimlico is used as the default infrastructure in:

  • Official ERC-4337 documentation examples
  • Safe’s AA implementation tutorials
  • Coinbase Smart Wallet infrastructure (Base chain)
  • Countless DApp integrations via permissionless.js

Related Terms

Sources

Last updated: 2026-04