Bundler

Powering Seamless Transactions in Web3

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Introduction

In blockchain’s early years, using decentralized applications meant dealing with confusing wallet setups, network fees, and cryptic transaction errors. For most users and enterprises, the friction was too high.

Today, Account Abstraction (ERC-4337) is changing that. It allows wallets to behave more like smart accounts — programmable, user-friendly, and automated. At the center of this new architecture sits an invisible but essential component: the bundler.

A bundler is the engine that connects users’ smart wallets to the blockchain. It gathers signed operations, pays gas on behalf of users, and ensures transactions run smoothly. Without bundlers, account abstraction would remain a concept rather than a working ecosystem.

This page explains what bundlers are, how they work, and why they’re becoming a cornerstone of modern Web3 infrastructure.

What Exactly Is a Bundler?

1

Simple Definition

A bundler is a network service that collects individual UserOperations from smart wallets and submits them together to the blockchain. It acts as a bridge between the user and the network, handling gas fees, batching transactions, and improving performance.

In technical terms, it operates as an off-chain node that communicates with the blockchain’s EntryPoint contract to process multiple operations at once.

2

In Everyday Terms

Imagine a courier service. Instead of sending one package at a time, it collects many parcels and delivers them together. The process is faster, cheaper, and easier to manage. A bundler works the same way for blockchain transactions, it picks up multiple requests from users and delivers them to the blockchain in one combined batch.

3

Why It Exists

Before bundlers, every user had to handle their own gas fees, token approvals, and network details. Each transaction required direct blockchain interaction.

Account Abstraction introduced UserOperations, a flexible transaction format that separates who creates a transaction from who sends it. But this model needed a trusted component to gather and relay those operations.

Bundlers exist to fill that role; simplifying interaction, reducing costs, and enabling seamless automation.

Why Bundlers Matter

Bundlers are more than a technical innovation; they redefine user experience in decentralized systems.

Simplify User Experience

Users can perform blockchain actions, like swapping tokens, buying NFTs, or signing approvals, without managing gas or keys.

The bundler abstracts all technical details, allowing apps to feel as simple as traditional fintech interfaces.

Enable Gasless Transactions

Bundlers work with Paymasters to sponsor gas fees.

This setup enables “gasless” experiences, where users transact using stablecoins or even without holding ETH at all, a critical step toward mainstream adoption.

Improve Efficiency

By combining multiple operations into a single submission, bundlers reduce network congestion and total gas spent per action. They optimize how data moves from users to the blockchain, improving throughput and cost efficiency.

Support Smart Wallets

Bundlers make smart contract wallets functional. They deliver the operations those wallets generate, ensuring they reach the blockchain safely and consistently, the same way a miner includes transactions in a block.

Accelerate Web3 Adoption

By hiding the complexity of blockchain interaction, bundlers make decentralized applications intuitive for both consumers and enterprises. They enable experiences that feel as smooth as logging into a banking app.

How a Bundler Works (Simplified Flow)

User Signs an Operation

A user initiates an action through a smart wallet (for example, sending tokens or approving a transaction).

Wallet Sends the UserOperation

The wallet packages the action into a UserOperation and sends it to a bundler rather than the blockchain directly.

Bundler Collects and Groups Operations

The bundler verifies each request, groups compatible operations, and prepares them for submission.

Bundler Submits the Batch

The bundler calls the blockchain’s EntryPoint contract and submits all grouped operations in one bundled transaction.

Gas Payment and Reimbursement

The bundler pays the gas initially. Later, it gets reimbursed by either the user’s smart account or a Paymaster sponsoring the fee.

This process happens seamlessly in seconds. You can think of the bundler as a reliable delivery service ensuring your transactions reach the blockchain without delay or confusion.

Bundlers in the Web3 Ecosystem

Bundlers are now integral to networks that support Account Abstraction. They power many of the most advanced smart wallets and infrastructure projects.

Bundler Provider Language / Stack Key Strength
Alchemy Rust Reliable, production-grade bundling API trusted by major dApps
StackUp Go Fast and scalable for enterprise and high-volume use cases
Infinitism TypeScript Official ERC-4337 reference implementation maintained by Ethereum researchers
Skandha (Etherspot) TypeScript Multi-chain support and SDK integration for wallets
Voltaire Python Flexible, research-focused implementation with strong developer community

Each bundler shares a common goal: to make blockchain interactions frictionless, affordable, and developer-friendly.

These projects are helping the ecosystem mature by offering standardized APIs, monitoring tools, and open-source references that any project can adopt.

Real-World Use Cases

Smart Wallets

Wallets like Argent and Safe rely on bundlers to process user operations and enable sponsored gas payments.

DeFi Platforms

Bundlers help trading and staking apps let users interact without holding ETH for gas. This reduces friction and increases participation.

Gaming dApps

In Web3 games, players perform hundreds of actions. Bundlers allow these to happen instantly and gas-free, creating smoother gameplay.

Enterprise Workflows

Companies automate complex, multi-step blockchain operations, such as compliance checks or asset transfers, through batched bundler submissions.

NFT Platforms

Marketplaces use bundlers to support single-click NFT purchases or listings, combining multiple operations (approval + transfer + mint) in one go.

Key Benefits for Businesses

Better Conversion Rates

By removing wallet setup steps and gas prompts, bundlers shorten the path from intent to action. More users complete their transactions, which directly improves conversion metrics.

Lower Costs

Bundling transactions reduces network overhead and total gas consumption per operation. Enterprises running large dApps can save significant operational costs.

User Retention

Users stay engaged when transactions “just work.” A frictionless, mobile-friendly experience builds trust and loyalty, crucial for any Web3 product.

Multi-Network Reach

Bundlers operate across EVM-compatible chains, allowing dApps to reach multiple ecosystems without rewriting transaction logic.

Future-Proof Infrastructure

As ERC-4337 adoption grows, bundlers will become the standard gateway for user operations. Integrating them early ensures scalability and long-term compatibility.

Challenges and Considerations

Centralization Risk

Right now, a small number of providers operate most bundlers. Over-reliance on a few players could create single points of failure, which contradicts Web3’s decentralized vision.

Fairness and Ordering

Bundlers control the order in which transactions enter the blockchain. Establishing transparent rules prevents manipulation and ensures fairness.

Economic Models

Bundlers need incentives to process operations efficiently. Balancing costs between users, paymasters, and bundlers is still an evolving challenge.

Security

Since bundlers handle user operations off-chain, they must validate input carefully to avoid spam or malicious payloads. Robust rate-limiting, whitelisting, and signature verification are essential safeguards.

Despite these hurdles, the community is developing decentralized bundler networks and open-governance models to address them. These innovations promise a safer, fairer, and more competitive market for bundler services.

Bundler vs. Relayer vs. Validator

To understand the unique role of bundlers, it helps to compare them with familiar blockchain components.

Aspect Bundler Relayer Validator
Role Packages and submits multiple UserOperations Sends single transactions Confirms blocks on-chain
Scope ERC-4337 smart wallets Classic Web3 applications Blockchain consensus
Gas Handling Pays gas, reimbursed by paymaster or wallet Paid by user or app Receives block rewards
Purpose Simplify and scale user transactions Enable meta-transactions Secure and validate the network

Bundlers don’t replace validators or relayers; they complement them. They operate one layer above consensus, ensuring that smart wallet activity reaches the blockchain efficiently.

Bundlers and Account Abstraction (ERC-4337)

Bundlers form one pillar of the ERC-4337 architecture. The others, Smart Accounts, EntryPoint, and Paymasters, work alongside it to create seamless transaction flows.

  • Smart Accounts: Wallets controlled by programmable logic rather than private keys
  • EntryPoint: The on-chain contract that verifies and executes bundled operations
  • Paymaster: A smart contract that sponsors gas fees on behalf of users
  • Bundler: The off-chain service that collects, validates, and submits all user operations to the EntryPoint

Together, these components replace the old wallet model with a modular, user-centric system. They allow businesses to build apps where blockchain complexity disappears, and end users interact with clean, intuitive interfaces.

Future of Bundlers

Bundlers are still evolving, and the next few years will define their maturity. Here are four trends shaping their future:

Decentralized Bundler Networks

Rather than relying on a few providers, ecosystems are moving toward open networks where many independent bundlers compete to include user operations. This model strengthens security and prevents monopolies.

Bundler Marketplaces

Dynamic fee markets are emerging, letting bundlers bid for inclusion opportunities. Users and paymasters will soon be able to choose bundlers based on performance, reputation, and cost.

Cross-Chain Bundling

Future bundlers will operate across rollups and Layer-2 networks, aggregating operations from multiple chains and routing them intelligently. This evolution will unify fragmented ecosystems.

Automated Fee Optimization

AI-powered bundlers could monitor gas fluctuations and optimize submissions automatically, minimizing costs for both users and sponsors.

Together, these advancements will make bundlers one of the most important middleware layers in blockchain, comparable to what payment gateways are in traditional finance.

Frequently Asked Questions

Common questions and answers about bundler, their implementation, and practical considerations for businesses and developers.

Bundler FAQ

Only if your wallet supports Account Abstraction (ERC-4337). Traditional wallets like MetaMask interact directly with the blockchain and don’t need one.

Yes. Developers and organizations can deploy open-source bundlers to manage their ecosystem’s transactions or reduce dependency on external providers.

Not exactly. A bundler connects to a node but runs additional off-chain logic to batch and submit transactions efficiently.

Either the user’s smart wallet pays, or a Paymaster sponsors the gas. The bundler pays upfront and is later reimbursed.

No. Relayers forward individual transactions, while bundlers package multiple user operations and send them together. Bundlers are purpose-built for the ERC-4337 framework.

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