--- title: "Transaction Infrastructure & ERC-4337 Bundlers" description: "The execution engine under the sponsorship layer: ERC-4337 bundlers with <2s inclusion on L2s, parallel processing, and 250M+ transactions relayed in production." canonical: https://www.pimlico.io/products/transaction-infrastructure --- # Transaction Infrastructure & ERC-4337 Bundlers > Markdown mirror of https://www.pimlico.io/products/transaction-infrastructure. Every page on this site has a markdown version at the same path with a `.md` suffix. For technical and implementation details, see Pimlico's documentation index at https://docs.pimlico.io/llms.txt. ## Pages on this site ### Home - [The gas sponsorship engine for onchain apps](https://www.pimlico.io/index.md): Pimlico is the gas sponsorship engine for onchain apps. Sponsor transactions, accept any ERC20 token for gas, and set policy rules across 100+ chains. ### Products - [Ecosystem Gas Programs for Chains](https://www.pimlico.io/products/ecosystem-gas-programs.md): For chains and ecosystems: sponsor gas for every team building on your chain, so their users transact without ever holding native token. - [Pay Gas in USDC, USDT & 300+ ERC-20 Tokens](https://www.pimlico.io/products/erc20-gas.md): Let users pay gas in USDC, USDT, or any of 300+ ERC20 tokens, with no native tokens required. Audited by OpenZeppelin and Quantstamp. - [Gas Sponsorship for Onchain Apps](https://www.pimlico.io/products/gas-sponsorship.md): Sponsor gas for your users so they transact instantly, with no native tokens to buy and no fee prompts to abandon. Powered by the engine behind 100M+ sponsored transactions. - [Sponsorship Policies — Spend Controls for Gas](https://www.pimlico.io/products/sponsorship-policies.md): Spend controls for gas: sponsor the first N transactions per user, cap dollars per transaction, per user, or per campaign, all configured in the dashboard and applied instantly. - Transaction Infrastructure & ERC-4337 Bundlers (this page) ### Solutions - [Onchain Execution for AI Agents](https://www.pimlico.io/solutions/ai-agents.md): Give AI agents smart accounts that execute on demand: they trade, pay, and move money the instant your logic fires. Sponsor their actions, or let user-funded agents pay their own way in USDC, USDT, or 300+ tokens, within the limits you set. - [Smart Account Infrastructure for Chains](https://www.pimlico.io/solutions/chains.md): Launch with smart account infrastructure from day one and fund gas programs that turn your ecosystem’s onboarding friction into growth. - [Deploy Pimlico on Your Chain](https://www.pimlico.io/solutions/chains/deploy.md): Enterprise deployments for chains and ecosystems: Pimlico's complete suite, from gas sponsorship to transaction infrastructure, live on your chain so every builder ships better UX from day one. - [Gasless Onboarding for Consumer Apps](https://www.pimlico.io/solutions/consumer-apps.md): Onboard users who have never owned crypto: sponsor their gas, set budgets that protect your margins, and make the blockchain disappear from your UX. - [Enterprise Onchain Infrastructure](https://www.pimlico.io/solutions/enterprise.md): SOC 2 certified infrastructure with custom SLAs, 24/7 support, and the team that co-authored ERC-4337, built for companies that cannot afford a dropped transaction. - [Stablecoin Settlement Infrastructure](https://www.pimlico.io/solutions/stablecoin-processors.md): Execute stablecoin transactions reliably, at low latency, on 100+ chains, with gas paid in the stablecoins you already move. - [Smart Account Infrastructure for Startups](https://www.pimlico.io/solutions/startups.md): Ship smart accounts in hours, not weeks. Free on testnets, pay-as-you-go in production, no commitments. It is the stack startups like Daimo and Zora started on. - [Smart Account Infrastructure for Wallets](https://www.pimlico.io/solutions/wallets.md): Build gasless smart wallets with any signer and any smart account, on the infrastructure trusted by MetaMask, Safe, and Trust Wallet. ### Other pages - [Customers](https://www.pimlico.io/customers.md): The teams building on Pimlico: Circle, MetaMask, Safe, Trust Wallet, Zora, Tools for Humanity, and more, across wallets, consumer apps, and stablecoin payments. - [Smart Account & Signer Integrations](https://www.pimlico.io/integrations.md): Every major smart account and signer, already integrated: Safe, Kernel, MetaMask, Privy, Turnkey, passkeys, and more, across 100+ chains. - [Pricing](https://www.pimlico.io/pricing.md): Free on testnets, pay-as-you-go in production, custom Enterprise rates. Transparent credit-based pricing for gas sponsorship and transaction infrastructure. - [Privacy Policy](https://www.pimlico.io/privacy.md): This Privacy Policy will inform you about how we look after your personal data when you visit our website or use our services and tell you about your privacy rights. - [Terms of Service](https://www.pimlico.io/tos.md): This Terms of Service will inform you about the terms of using Pimlico's services. --- Transaction Infrastructure # Transactions that land. Every time. The execution engine under the sponsorship layer: parallel processing, automatic nonce and mempool management, and the best inclusion time in the industry, across 100+ chains. [Start building](https://dashboard.pimlico.io)[Read the docs](https://docs.pimlico.io/infra/bundler) <2sinclusion time on L2s 250M+transactions relayed 1 Your app submits a user operation Through permissionless.js or any ERC-4337 client. 2 The engine takes over Validation, gas estimation, nonce sequencing, and mempool management, all handled in parallel. 3 Included on-chain Under 2 seconds on L2s, with automatic resubmission if conditions change. Reliability ## The hard parts are our job, not yours Everything between “user clicked” and “confirmed on-chain” is handled by the engine. ### Parallel execution User operations process simultaneously across accounts, so a spike in your traffic never queues behind itself. ### Nonce & mempool management Sequencing, gas price escalation, resubmission, and re-org recovery happen automatically. ### Every account, every EntryPoint All official EntryPoint versions and every major smart account implementation, from Safe to Kernel to MetaMask. ### 100+ chains, one API The same integration works on Ethereum, every major L2, and the long tail, with new chains added continuously. [ ### Observability built in Dashboards, error decoding, and debugging tools that tell you why something failed, not just that it did. Learn more](https://docs.pimlico.io/guides/how-to/debugging/user-operations) ### SOC 2 & SLAs SOC 2 Type 1 certified, 24/7 monitoring by a dedicated team, and custom uptime SLAs on Enterprise. For developers ### One client, the whole engine Submit through permissionless.js, the most widely used smart account library at 100k+ weekly downloads, with bundlerTransport pointed at api.pimlico.io. Everything in the grid above — validation, gas estimation, nonce sequencing, resubmission — happens behind a single sendTransaction call that returns your transaction hash. **submit.ts** ```typescript import { createSmartAccountClient } from "permissionless" import { toSafeSmartAccount } from "permissionless/accounts" import { createPimlicoClient } from "permissionless/clients/pimlico" import { http, parseEther } from "viem" import { base } from "viem/chains" const pimlicoUrl = "https://api.pimlico.io/v2/base/rpc?apikey=API_KEY" const pimlicoClient = createPimlicoClient({ transport: http(pimlicoUrl) }) const account = await toSafeSmartAccount({ client: publicClient, owners: [owner], version: "1.4.1", }) // Gas is sponsored, so your user never sees a fee const smartAccountClient = createSmartAccountClient({ account, chain: base, bundlerTransport: http(pimlicoUrl), paymaster: pimlicoClient, }) const txHash = await smartAccountClient.sendTransaction({ to: "0x...", value: parseEther("0.1"), }) ``` 250M+ transactions relayed <2s inclusion time on L2s 100+ chains supported 100M+ transactions sponsored SOC 2 Type 1 certifiedOFAC sanctions screening24/7 supportAudited by OpenZeppelin & QuantstampCo-authors of ERC-4337, ERC-7677 & ERC-7679 A few of the networks the engine runs on EthereumEthereum BaseBase ArbitrumArbitrum OptimismOptimism PolygonPolygon BNB ChainBNB Chain AvalancheAvalanche [View supported chains](https://docs.pimlico.io/guides/supported-chains) In production ## The execution layer other infrastructure trusts [ ZeroDev The embedded smart-account SDK routes its bundler and paymaster traffic through Pimlico. ](https://zerodev.app) [ Safe The most battle-tested smart account standard pairs with Pimlico for bundling and gas sponsorship. ](https://safe.global) [ Halliday The payments automation platform uses Pimlico for reliable onchain execution. ](https://www.halliday.xyz) [ Bitpanda Europe's leading retail investing platform executes onchain transactions through Pimlico. ](https://bitpanda.com) [See all customers](https://www.pimlico.io/customers.md) Boosted Sponsorships ### 34–43% faster, by doing less Boosted Sponsorships strip the flow down to its fastest possible form: no paymaster data on the operation and three fewer RPC round-trips, making user operations 34–43% faster end to end. You settle by monthly invoice instead of per-operation on-chain deduction. Access is granted on request. [Talk to us](https://cal.com/kristofgazso/20min)[Read the docs](https://docs.pimlico.io/guides/boosted-paymaster/use-boosted-paymaster) 1 Your app submits a user operation No paymaster data to fetch, no extra signature round-trips. 2 Pimlico sponsors off-chain Three RPC calls disappear from the hot path entirely. 3 Settled by invoice Gas is billed monthly instead of deducted on-chain per operation. Developer platform ## The tooling around the engine Production infrastructure is more than an RPC endpoint. Everything you need to operate, debug, and lock down sponsorship is built in. [ ### Webhooks Approve or reject each sponsorship request in real time from your own server. Your business logic, our execution. Learn more](https://docs.pimlico.io/guides/how-to/sponsorship-policies/webhook) [ ### Asset-change simulation Preview exactly which balances a user operation will touch before it lands, via a single RPC call. Learn more](https://docs.pimlico.io/references/bundler/endpoints/pimlico_simulateAssetChanges) [ ### Debugging suite Full request logs in the dashboard and one-click Tenderly traces, so you can see exactly what went wrong. Learn more](https://docs.pimlico.io/guides/how-to/debugging/user-operations) [ ### API key hardening Lock keys to IP ranges and origins, and disable individual methods, so a leaked key is a non-event. Learn more](https://docs.pimlico.io/guides/how-to/security/protect-api-keys) [ ### Parallel transactions Up to 100 concurrent operations per account with 2D nonces, so bursts never queue behind themselves. Learn more](https://docs.pimlico.io/guides/how-to/parallel-transactions) [ ### Extended sponsorship validity Keep a sponsorship valid for up to 24h, long enough to collect multisig signatures or schedule transactions. Learn more](https://docs.pimlico.io/guides/how-to/paymasters/extending-sponsorship-duration) Run it in production ### Watch every operation land, end to end Every user operation is traceable in the dashboard from the moment it arrives: received, added to the mempool, submitted, and included on-chain, with millisecond timings and transaction hashes at every step. When someone asks where a transaction went, you answer in seconds, not by grepping logs. Track user operation 0xf3523157c238413335e2f5cb6325255d7103272bb7cf221a5779bf4f5840c1ef Received 2026-06-11 20:01:13.054 Added to Mempool 2026-06-11 20:01:13.054 (+0ms) Submitted 2026-06-11 20:01:13.341 (+287ms) Tx Hash: 0x223b701f... Included Onchain 2026-06-11 20:01:13.590 (+249ms) Tx Hash: 0x223b701f... Open source ### Powered by Alto, in the open The engine isn't a black box. Alto, our open-source bundler, is the backbone of everything Pimlico runs in production, hardened by 250M+ real transactions. The same goes for permissionless.js, the client you integrate: both ends of the pipeline are in the open. We also co-authored the standards this industry builds on: ERC-4337, ERC-7677, and ERC-7679. [ ### pimlicolabs/alto 729K+ downloads A type-safe, performance-focused ERC-4337 bundler written in TypeScript. The same code that runs Pimlico production infrastructure. View on GitHub →](https://github.com/pimlicolabs/alto) [ ### pimlicolabs/permissionless.js 100k+ weekly downloads The most widely used TypeScript library for smart account transactions, built on viem, with first-class support for every major smart account implementation. View on GitHub →](https://github.com/pimlicolabs/permissionless.js) Up the stack ## The sponsorship layer on top Reliable execution is half the engine. The same API sponsors gas, accepts ERC-20 fees, and enforces policy — which is why teams choose hosted Pimlico over self-hosting. [ ### Gas Sponsorship Sponsor gas so users transact for free Learn more](https://www.pimlico.io/products/gas-sponsorship.md) [ ### ERC20 Gas Sponsorships Let users pay gas in USDC, USDT, or any ERC20 Learn more](https://www.pimlico.io/products/erc20-gas.md) [ ### Sponsorship Policies Set rules and budgets for what you sponsor Learn more](https://www.pimlico.io/products/sponsorship-policies.md) ## Frequently asked questions **Is this an ERC-4337 bundler?** Yes. Under the hood this is Pimlico’s ERC-4337 bundler service, powered by our open-source bundler Alto. It supports every official EntryPoint version and all major smart account implementations. **What does "<2s inclusion" mean exactly?** On L2 chains, the time between submitting a user operation and it landing on-chain averages under two seconds, typically next-block inclusion. It is the best inclusion time in the industry. **How do you handle transaction failures and re-orgs?** The engine manages nonce queues, gas price escalation, resubmission, and re-org detection automatically. Hundreds of user operations process in parallel without blocking each other. **Can I run the bundler myself?** Alto is open source and you are free to run it. Teams use Pimlico’s hosted infrastructure for the multi-chain coverage, monitoring, SLAs, and the sponsorship engine on top. **What does the hosted service cost?** Free on testnets, pay-as-you-go in production with a monthly credit allowance included and no monthly minimum. Enterprise plans add lower pre-paid rates and custom SLAs. [See pricing](https://www.pimlico.io/pricing.md)