What Is Fermi Swap and How Do Approvals and Gas Work?
Fermi swap is an Ethereum exchange for trading tokens from your wallet. A Fermi token swap is filled from the exchange’s own token inventory, while your wallet authorises the trade and pays network costs. When you are ready to exchange tokens without depositing them on a centralised exchange, use Fermi swap from your wallet.
Is Fermi swap available on Ethereum?
Yes, Fermi is an Ethereum based exchange. You need the token you want to sell and some ETH in your wallet. ETH pays for gas, the network charge for processing a transaction.
Four things matter on your first trade:
- A token may need approval before you sell it.
- Approval and swapping can each use gas.
- The amount you receive depends on the quoted price.
- A failed swap can still cost gas.
An approval lets the exchange’s smart contract spend a set amount of your token. A smart contract is code that carries out the trade on Ethereum. Approval does not make the swap: it is a separate transaction that may need its own wallet confirmation.
Gas is charged for work done on Ethereum. Its price changes with network demand, and a swap usually uses more gas than an approval. If your wallet has USDC but no ETH, you may be unable to approve or swap the USDC.
The quoted amount also affects your cost. Compare the WBTC you would receive for your USDC with its current market value. The difference may matter more than gas on a large trade; gas may matter more on a small one.
A transaction can fail after Ethereum processes it. You then pay for the work already done, although the tokens you meant to swap stay in your wallet. A successful approval can remain in place even if the later swap fails.
Can I swap tokens directly from my wallet with Fermi?
Yes, you can trade from your wallet without first depositing tokens at a centralised exchange. Choose the token and amount to sell, then review what you expect to receive. If your wallet asks for approval, check the token and spending amount before confirming it.
Once approval is confirmed, review the trade again and authorise the swap. Check the expected output and your wallet’s gas estimate before you sign. You can look up the transaction on Etherscan, an Ethereum transaction record, to see whether it succeeded.
Here is an illustrative first trade cost. Suppose an approval uses 50,000 gas and a swap uses 150,000 gas. At 2 gwei per gas unit, they cost 0.0004 ETH together; at an example ETH price of $2,500, that is $1. Your actual cost depends on gas prices and the work each transaction uses.
Each transaction may enter an Ethereum block in seconds, but a busy network can make it take longer. A first trade can need two confirmations: one for approval, then one for the swap. Later trades of the same token may use an existing allowance, which is the amount already approved.
Why did my swap fail?
A swap may fail because the price moved, the approved amount was too small, or the trade could not be filled as requested. Check your wallet balance, ETH for gas, and any minimum amount you agreed to receive. If approval succeeded, check its allowance before paying to approve again.
Keep the safety check brief but firm: confirm the token and spending amount shown in your wallet. An unlimited allowance lets the approved contract spend more of that token later, so choose a smaller amount when it suits your trade. Before you sign, ask yourself: is the expected amount you receive still worth the quoted price and the full first-trade cost?