Gasless Transaction

A dApp or relayer pays the network gas fees on behalf of the user. The user signs a message authorizing an action, which is then wrapped into a standard transaction by the sponsor. This is common in onboarding flows where the application subsidizes initial interactions.

• User Experience: Removes the need for users to acquire ETH or MATIC before their first transaction.
• Implementation: Uses a system of gas tanks or forwarder contracts to manage and pay for bundled transactions.

A core component of Account Abstraction (ERC-4337) and certain L2s. A paymaster contract validates a user's transaction and can decide to pay for its gas, often in exchange for payment in an ERC-20 token or based on predefined rules.

• Flexible Payment: Users can pay fees in USDC, DAI, or any token the paymaster accepts.
• Sponsored Sessions: Can enable session keys for gasless interactions over a set period or for specific contract calls.

Decentralized networks of nodes (relayers) that receive signed user messages, submit the corresponding transactions to the network, and cover the gas cost. They are often compensated via off-chain agreements or system tokens.

• Decentralization: Avoids single points of failure compared to a single dApp sponsor.
• Examples: The GSN (Gas Station Network) pioneered this model, providing a standardized protocol for relayers.

The foundational cryptographic primitive. Instead of sending a standard transaction, the user signs an EIP-712 structured message containing the intended action. This signature is then used by a relayer or smart contract to execute the transaction.

• Security: The user's private key never leaves their custody; they only sign a message.
• Nonce Management: Systems must carefully manage meta-transaction nonces to prevent replay attacks.

Multiple user actions are aggregated into a single transaction by a relayer, dramatically reducing the effective gas cost per action. This is a key scaling benefit of gasless architectures.

• Cost Efficiency: Amortizes the fixed base cost of a transaction over many operations.
• Use Case: Ideal for micro-transactions or games where many small state updates are required.

ERC-4337 (Account Abstraction) enables smart contract wallets to natively support gasless flows. The wallet's logic can specify custom validation, allowing a paymaster to cover fees or allowing fees to be paid in any token.

• Native Feature: Gas sponsorship becomes a programmable feature of the account itself.
• User Operation: The new transaction type (UserOperation) is inherently designed for relayed execution.

This model involves pre-funding a shared gas tank (smart contract) that a relayer or paymaster draws from to sponsor user transactions. It's common for wallet providers and dapps.

• User Experience: Users interact without ever holding gas tokens.
• Business Model: Costs can be recouped via subscription fees, transaction fees on successful actions, or covered as a user-acquisition cost by the project.

Gasless flows rely on off-chain signatures (e.g., EIP-712 structured data) for authorization. These signed messages represent user intent without being on-chain transactions.

• Batching: Multiple signed user operations can be aggregated into a single blockchain transaction by a relayer, dramatically reducing the effective gas cost per user action.
• Reduced Overhead: Signatures are verified on-chain, but the bulk of the data and logic can remain off-chain until final settlement.

Networks with inherently lower or zero gas fees for users indirectly enable gasless experiences. While validators pay fees, the cost can be so minimal that projects absorb it seamlessly.

• Polygon PoS: Many dapps sponsor transactions on this Ethereum sidechain due to its low fee environment.
• Optimism & Arbitrum: Layer 2 rollups where transaction fees are significantly cheaper, making sponsored tx models more economically viable.

A gasless transaction is a meta-transaction, where a user signs a message off-chain. This signed message is then submitted to the network by a relayer (a separate server or smart contract) that pays the gas fee. The relayer is reimbursed, often by the dApp or through a fee abstraction protocol. This decouples the need to hold ETH for gas from the ability to execute actions on Ethereum.

ERC-4337 is the Ethereum standard that natively enables gasless experiences through account abstraction. It introduces UserOperations, which are bundled by Bundlers and have their fees paid by Paymasters. This allows for:

• Sponsored transactions: A dApp or wallet pays the gas.
• Pay with ERC-20 tokens: Users pay fees in USDC or other tokens.
• Session keys: Pre-approved transactions that don't require repeated signing.

Before ERC-4337, standalone relayer networks like GSN (Gas Station Network) provided the infrastructure for meta-transactions. These systems required dApps to deploy custom RelayHub and Paymaster contracts to manage gas reimbursement logic and prevent spam. Today, services like Stackup, Biconomy, and Candide act as professional bundlers and paymaster providers for ERC-4337.

Gasless transactions are critical for onboarding and specific application logic:

• Onboarding: New users can mint an NFT or swap tokens without first buying ETH.
• Subscription Models: Apps can cover gas for premium users.
• Mass Airdrops: Projects can distribute tokens to thousands of wallets without requiring recipients to have gas.
• Improved UX: Removes a major friction point, making Web3 interactions feel more like Web2.

The party paying the gas (sponsor) must implement safeguards:

• Rate Limiting: Prevent a single user from spamming transactions.
• Whitelisting: Only allow specific actions or smart contracts.
• Reputation Systems: Used by relayers/bundlers to filter malicious UserOperations.
• Staked Deposits: In ERC-4337, paymasters must stake ETH, which can be slashed for misbehavior, aligning incentives.

Fee abstraction is the broader category that includes gasless transactions. It encompasses any method of decoupling fee payment from the transaction sender. This includes:

• Sponsored Gas (true gasless).
• Paying with ERC-20s via a paymaster.
• Credit/Debit Card Payments for gas, facilitated by a gateway. The goal is to make the underlying blockchain's native token invisible to the end-user.

A gasless transaction is a meta-transaction where a user signs a message off-chain. A relayer (often the dApp itself or a specialized service) then submits this signed message to the blockchain, paying the gas fee on the user's behalf. The core mechanism relies on a verifying contract that validates the user's signature and executes the intended logic.

• User Flow: Sign → Relayer → On-chain Verification → Execution.
• Key Contracts: EIP-2771 for secure meta-transactions, EIP-2612 for gasless token approvals.

The entity covering the gas cost is called a sponsor or paymaster. Common models include:

• dApp Pays: The application subsidizes fees to improve UX, treating it as a customer acquisition cost.
• Paymaster Contract: A smart contract that holds funds and logic to decide which transactions to sponsor, potentially using alternative tokens for payment (e.g., paying gas in USDC).
• Account Abstraction (ERC-4337): A generalized framework where a UserOperation can specify a paymaster, enabling sophisticated sponsorship rules and batch payments.

Gasless designs introduce new trust vectors and attack surfaces.

• Relayer Centralization: Users must trust the relayer to submit their transaction promptly and honestly. A malicious or offline relayer can censor transactions.
• Replay Attacks: Signed messages must include a nonce and be constrained to a specific domain to prevent reuse on different chains or contracts.
• Sponsor Risk: A malicious paymaster could front-run or manipulate transaction ordering. Secure implementations use EIP-2771's _msgSender() to prevent address spoofing.

The long-term economics of gas sponsorship are critical.

• Cost Absorption: dApps must budget for gas costs, which can become unsustainable during high network congestion.
• Sybil Resistance: Without a cost barrier, systems are vulnerable to spam. Sponsors often implement rate-limiting, proof-of-humanity, or staking requirements.
• Monetization: Some paymasters may charge users a small premium in a stablecoin, converting it to native gas off-chain, creating a business model.

Gasless transactions significantly improve onboarding and UX by hiding blockchain complexity, but often at the cost of decentralization.

• Pro: Users unfamiliar with crypto can interact immediately; no need to acquire ETH or MATIC first.
• Con: Reliance on a centralized relayer service creates a single point of failure, contradicting censorship-resistant ideals.
• Hybrid Models: Some systems offer gasless onboarding but allow users to graduate to self-custodied gas payment for high-value transactions.

Several protocols and standards enable gasless functionality.

• OpenZeppelin Defender: Provides a managed relayer service for meta-transactions.
• GSN (Gas Station Network): An early decentralized relayer network (largely superseded by Account Abstraction).
• ERC-4337 (Account Abstraction): The current standard, allowing smart contract wallets to natively support paymasters and batch transactions, making gasless flows a wallet-level feature.
• Polygon & Biconomy: Networks and infrastructure providers offering SDKs for easy gasless integration.