Nobody likes hidden fees, and crypto has a reputation for them. So let us lay out exactly what a swap costs in Simple Base Swap, where each cost comes from, and what you can do about it.
The three costs of any swap
1. The service fee. This is what we charge for the product. It is 0.7% and it is already included in the rate you see on screen. If the app shows that you will receive 413 USDC, you will receive 413 USDC. On top of that, the exchange provider we use, 0x, charges approximately 0.15% on the output amount. There are no other charges from us, ever.
2. The network fee. Every transaction on a blockchain pays a small fee to the network itself, in ETH. This money does not go to us. On Base this is one of the smallest numbers you will encounter in crypto, typically well under a cent. It is the reason we built on Base in the first place.
3. Slippage. This one is not a fee at all, but it can cost you money, so it belongs on the list.
What slippage actually is
Between the moment you see a quote and the moment your transaction lands on the blockchain, a few seconds pass. In those seconds, other people are trading the same tokens, and the price can move.
Slippage tolerance is the answer to one question: how much worse than the quoted price are you willing to accept before the trade should be cancelled? With the default 0.5%, if the price moves against you by more than half a percent, the swap fails and your funds stay where they were. You pay only the tiny network fee for the failed attempt.
How to choose a slippage setting
For large, liquid pairs like ETH and USDC, the default 0.5% is right and you should not think about it again.
For small or volatile tokens, the price genuinely moves faster, and 0.5% can cause repeated failed swaps. Raising the tolerance to 1% or a little more usually fixes it. Raise it gradually and only as much as needed.
What you should not do is set a very high slippage on a whim. A 10% tolerance means you have agreed in advance to receive up to 10% less than quoted, and on thin markets that outcome is not rare. If a token needs double-digit slippage to trade at all, that is useful information about the token.
How we find your rate
When you request a quote, we do not check one exchange. The request goes through 0x, which searches across the decentralized exchanges on Base, including Uniswap and Aerodrome among others, and routes your swap to whichever venue or combination of venues gives the best output. Sometimes a single swap is quietly split across two or three exchanges behind the scenes. You see one number; the routing work happens for you.
A worked example
Say you swap 0.25 ETH for USDC and the screen shows 413 USDC.
That 413 already accounts for our 0.7% service fee and the routing across exchanges. The 0x provider fee of roughly 0.15% applies on the output. The network fee will be a fraction of a cent in ETH. With slippage at 0.5%, the absolute minimum you can end up with is about 411 USDC, and if the market moves more than that, the trade cancels instead of executing badly.
That is the whole picture. No deposit fees, no withdrawal fees, no monthly anything.