How to Build zkSync Era Dapps with Paymasters

zkSync Era has native account abstraction, so developers can build smart contract accounts (SCAs) that control transaction authorization and execution. A paymaster is an optional contract that can cover a transaction’s network fee or collect payment according to its own rules. Together, they let a dapp offer flows such as sponsored actions or fees paid through a supported token.

The key decision is who pays, not whether the transaction has a fee. If your app sponsors gas, your project bears the cost. If a paymaster collects a token or another form of reimbursement, users still pay under the terms your contracts enforce. You need to explain that arrangement before a user signs.

A practical decision checklist:

• Use a standard wallet flow if your dapp does not need custom authorization or fee handling.
• Consider a smart account when you need programmable validation or a tailored signing experience.
• Add a paymaster only if sponsorship or an alternative payment flow is worth the extra contract, monitoring and support work.

Native AA is a protocol capability, not a guarantee that every wallet, contract or dapp integration supports every custom account and paymaster flow.

A conventional externally owned account (EOA) signs transactions with a private key. A smart account is a contract account: its logic decides whether a transaction is valid and what actions it can perform. That logic can support more than one authorization pattern, but the account’s own contract rules remain decisive.

A typical paymaster transaction follows this broad sequence:

1. The user’s wallet or dapp prepares a transaction for the smart account.
2. The account’s validation logic checks whether the requested action is authorized.
3. If a paymaster is involved, its policy checks whether it will cover the fee or accept the specified reimbursement.
4. The transaction executes, and the network fee is paid. The paymaster may then apply its defined settlement or accounting logic.

The exact data format and contract interfaces depend on the zkSync Era tooling and implementation you choose. Do not assume a paymaster is simply a user-facing toggle: it is on the transaction path and must be compatible with the account and the calls being made.

This is native zkSync Era account abstraction. Avoid treating it as interchangeable with an Ethereum ERC-4337 setup: tooling, transaction handling and integration assumptions can differ.

Choose the fee model before writing the paymaster. Your choice determines what users see, what your contracts must verify and where operating costs land.

Model	Who bears the cost	What to make clear
Sponsored transaction	Your project pays the network fee	Which actions qualify, and whether sponsorship can stop
Token reimbursement	The user pays through a supported token flow	Token accepted, amount or conversion rule, and any added charge
No paymaster	The user pays the network fee through their wallet	Fee estimate and what happens if the wallet cannot proceed

Sponsorship can reduce friction for a first action, but it creates a budget and abuse problem. Put limits around eligible operations, users or total spend. Consider how you will handle repeated requests, failed calls and traffic spikes. A token-payment flow can avoid asking users to hold the network’s fee token, but it adds price, liquidity and settlement questions that your policy must address.

Keep user consent explicit. Show which transaction is being sponsored or what token will be used for payment before approval. Do not describe a transaction as free if your project pays for it or if a paymaster later collects a fee. Keep a non-sponsored route available where possible, so users are not stranded if your sponsor runs out of funds or pauses service.

Start with the smart account, then connect the paymaster. zkSync Era account abstraction makes smart accounts and paymasters first-class parts of the transaction model, but your contracts still need to follow the network’s rules. A custom account should validate the intended authorizations, execute only permitted actions and handle the relevant transaction data correctly.

A practical implementation order is:

1. Define account behavior. Specify who can authorize transactions and what happens when validation fails.
2. Select a supported toolchain. Use zkSync Era-compatible compiler and development tools, and confirm their versions work with your contracts.
3. Build and test the account alone. Cover normal calls, invalid signatures or authorizations, reverts and account deployment.
4. Add the paymaster. Keep its sponsorship or reimbursement policy separate and narrowly scoped.
5. Test the combined flow. Confirm the account and paymaster agree on transaction data and failure handling.

Smart-account deployment may use a factory or a deployment flow integrated with a transaction. Plan for how your app identifies an account before and after deployment; do not assume every user already has a deployed contract account. Confirm the current deployment and tooling requirements for the specific account pattern you adopt.

Treat the paymaster like a limited spending authority. It can affect who pays a transaction fee, so a permissive policy may expose your project to unexpected cost or misuse. Restrict the calls it will sponsor and verify the transaction details your policy relies on. Avoid a rule that accepts any transaction simply because it came through your dapp.

Before deployment, decide:

• Which contract calls and methods qualify for sponsorship.
• Whether users, sessions or transactions need individual limits.
• How the paymaster’s funds are replenished and who can authorize that action.
• What your app does when a request is rejected, the paymaster is underfunded or a call reverts.
• How you will pause sponsorship and communicate that change.

For token reimbursement, check that the payment asset and amount are handled as intended. If a conversion or quote is involved, define how the amount is determined and what happens if it changes or expires. Never rely on a front-end display alone to enforce a payment rule; validate the rule in the contract path.

Keep privileged controls narrow, protect administrative keys, and monitor sponsored transactions and balances. A paymaster does not remove smart-contract risk: errors in authorization, accounting or limits can still cost the project or its users.

The dapp interface is part of the security model. Users need to understand whether they are approving an action, a sponsorship request or a token payment. Show the target action and relevant asset before a signature, and make it easy to review the transaction rather than presenting a vague “gasless” button.

Build the flow around clear states:

• Ready: Explain who pays the fee and which actions qualify.
• Requesting approval: Identify the account and transaction the user is authorizing.
• Submitting: Avoid implying that a click guarantees inclusion or success.
• Failed or unavailable: Explain whether the action failed, sponsorship was refused, or the user can retry with a normal fee-paying wallet flow.

Do not assume that every wallet will display custom account or paymaster information in the same way. Test with the wallets and account implementations your audience is expected to use. Make sure the interface does not ask users to approve a different transaction from the one described.

If your dapp lets users proceed without sponsorship, show that option clearly. If sponsorship is restricted or temporarily unavailable, state the consequence before asking the user to continue. Good error messages can prevent users from repeatedly signing requests they do not understand.

Test the account and paymaster together, not only as isolated contracts. A successful contract deployment does not prove that the wallet can construct the transaction, the account can validate it, or the paymaster will apply the intended policy.

Use a test checklist that includes:

• A valid sponsored transaction and a valid user-paid transaction.
• A call outside the paymaster’s allowed set.
• Invalid or missing authorization and an expired or otherwise unacceptable request, if your design uses one.
• Insufficient paymaster funds and a rejected sponsorship request.
• A reverting dapp call and the resulting fee or reimbursement behavior.
• Account deployment, repeat transactions and recovery from an interrupted user flow.

Check that the app’s displayed fee and payment explanation match contract behavior. Review logs and monitoring so your team can distinguish a rejected paymaster request from a failed account validation or dapp call. Test the exact compiler, account code, paymaster and wallet versions that you intend to ship.

Before production, verify current zkSync Era network settings and the requirements of your chosen toolchain. Keep deployment configuration and administrative access under review. If you upgrade contracts or change sponsorship rules, rerun the combined tests and communicate changes that affect what users pay.

There is no single fixed cost for every zkSync Era transaction. The network fee depends on the transaction and current conditions, while a paymaster changes the payer or payment route rather than eliminating the charge. Your project’s actual expense also depends on which calls it sponsors and how often users make them. Do not publish a flat “free” promise unless your policy and budget support it.

Common implementation mistakes include:

• Sponsoring every call: restrict eligible actions and set spend controls.
• Assuming all wallets support your setup: test the intended account and wallet combinations.
• Treating a paymaster as a substitute for account security: validate authorization and transaction scope in the account itself.
• Hiding reimbursement terms: state which token or payment rule applies before the user approves.
• Ignoring sponsor failure: offer a clear retry or user-paid route where practical.
• Testing only the happy path: check rejected calls, reverts, depleted funds and deployment edge cases.

Keep a live view of sponsored volume, paymaster balances, failures and policy rejections. Review that information against your budget and adjust limits deliberately. If your dapp changes its fee policy, update the interface and test suite together. The safest design is not the one with the fewest clicks; it is the one users can understand and your team can control.