SyncSwap lets users pay gas with supported ERC-20 tokens through its Paymaster on zkSync Era, so a swap can go through without native ETH in the wallet; the user still pays a fee in the selected token unless a sponsored or gas-free promotion applies. The detail that makes the process click is that this is fee abstraction, not a change to how the swap itself settles.
- Gas token: Choose an ERC-20 accepted by the Paymaster and keep it on zkSync Era.
- Allowance: Approve the Paymaster when the wallet requests permission to collect the fee.
- Balance: Leave enough of the token for both the swap amount and the estimated gas payment.
What SyncSwap is actually changing
SyncSwap is a decentralized exchange on zkSync Era whose Paymaster adds a token-payment layer around the transaction. The underlying network still accounts for execution in its native gas system. The Paymaster fronts that native fee to the transaction processor, then collects the equivalent amount from the user's ERC-20 balance.
That distinction matters. An ERC-20 token does not become a protocol-level gas token, and the pool contract does not pay the fee from the trade. The transaction carries account-abstraction data identifying the Paymaster, the chosen token and the minimum allowance. If the conditions are valid, the swap executes and the Paymaster settles the fee in tokens.
This is why the feature is not a Solidity Programming Language trick or a special property of a particular pool. It is application-level plumbing built on zkSync Era's native account-abstraction support. The same network architecture also allows a project or ecosystem partner to sponsor selected transactions, which is the separate case commonly described as gas-free.
The fastest path from decision to done
The practical route is short, but the order matters. First connect the wallet to zkSync Era and select the tokens for the trade. Then check the gas-payment selector before submitting the swap. If the chosen ERC-20 is supported and the wallet has enough of it, select that token instead of native ETH.
The Syncswap app is where the route, gas token and approval prompt come together. After the token is selected, the wallet may ask for an allowance. Approve only the token and spender shown by the transaction details, then return to the swap confirmation and review the final fee denomination.
The first use can feel like two transactions because an allowance may need to be established before the swap. That is normal for an approval-based Paymaster flow. A later swap with an adequate allowance usually removes that extra step, although the app can still request a new approval when the previous allowance is too small.
What the fee is, and what it is not
The ERC-20 gas payment is separate from SyncSwap's trading fee. The trading fee belongs to the selected liquidity pool and is reflected in the swap output. The Paymaster fee covers network execution and is charged in the token chosen for gas. A quote that looks attractive on the pool side can still require more token balance than expected if the wallet has not reserved room for both charges.
The same separation is useful when comparing SyncSwap with the Uniswap Protocol. The AMM route, price impact and liquidity determine the trade result; gas abstraction determines how the network fee is funded. Comparing only the displayed token output misses the operational difference. Compare the final received amount, the pool fee and the token-denominated network fee as three separate figures.
The edge cases that cause failed swaps
The most common failure is choosing a token that is not accepted by the current Paymaster configuration. “Pay gas in any token” describes the capability, not a promise that every ERC-20 in the wallet is available in the selector. If the token is absent, switching to one the interface offers is faster than trying to force the transaction through.
The second failure is spending the entire input balance. When USDC or USDT is both the swap input and the gas token, leave a buffer. The wallet must retain enough tokens for the Paymaster's estimate, and the final amount can change with gas conditions or the transaction's execution path.
The useful verdict is simple: ERC-20 gas is best when the wallet already holds stablecoins or another supported asset but has no native ETH. It removes the funding detour while preserving the normal SyncSwap trade flow. It does not remove the need to check the accepted token, allowance and combined balance before signing.