The One Mistake I Made on My First Matcha Swap

A token swap exchanges one cryptocurrency for another through a connected wallet. This is for anyone making their first swap and wondering why the full balance is not available to trade.

The mistake is simple: selecting “max” and leaving nothing behind for gas. Gas is the network fee paid to process a transaction. It is usually paid in the network’s native coin, not in the token being swapped.

I expected to turn my entire balance into another token. I connected my wallet, chose the token I held, selected the token I wanted, and clicked the option to use the maximum amount. The quote looked fine. The amount looked tidy. I approved the token and then tried to complete the swap.

That was when the plan stopped being tidy. The wallet still needed native coin to pay the transaction fee. I had left almost none. The swap could not be submitted, even though the balance shown for the token was large enough. The interface was not broken. I had spent the balance I needed to operate the wallet.

There can be a second step before the swap itself. An approval is a wallet permission allowing the exchange contract to use a chosen token. It is not the swap. The swap is the later transaction that exchanges the assets. Both steps may require gas.

What I do now

I first check the network. A network is the blockchain where the transaction will happen, such as Ethereum, Base, or Polygon. The wallet and the swap screen must point to the same one. Then I check which coin pays gas on that network.

Next, I enter a fixed amount instead of choosing “max.” I leave enough native coin for the approval and the swap, with some room for a changing fee. The exact amount depends on the network and current congestion, so I do not treat a tiny leftover as a safe buffer.

For a first attempt, I also make a small test swap. If I hold 100 units, I might start with 10 rather than moving all 100. I confirm the token name, network, quoted output, and minimum received amount before signing. The minimum received amount is the least the transaction will accept if the market moves while it is processing.

If I had to give my earlier self one sentence, it would be this: the balance you see is not always the balance you can spend. Keep the fee coin in the wallet, and use a deliberate amount.

That check is what settled my matcha swap routine. The page is where I now enter the pair, inspect the quote, and send the transaction, but the important habit comes before the click: reserve gas first.