You just swapped a token on Base and your wallet shows a confirmation. But what actually proves the swap happened the way you expect? The answer is not the notification popup, it is the transaction receipt and the event logs attached to it. Both are public, permanent, and readable by anyone with a block explorer. This article walks through what they are and how to read them.
What a transaction receipt is
Every transaction on Base produces a receipt once it is included in a block. The receipt is generated by the network itself, not by your wallet or by Simple Base Swap. It contains a small set of facts about what happened when the transaction executed:
- Status: whether the transaction succeeded or reverted.
- Gas used: how much of the gas limit the transaction actually consumed.
- Block number and timestamp: when it was included.
- Logs: a list of events emitted by the contracts involved.
You can find the receipt for any transaction by pasting its hash into Basescan, the block explorer for Base. If you have not used a block explorer before, see How to Use a Block Explorer for the basics.
The status field
The status field is the first thing worth checking. It is either "Success" or "Fail." A transaction can be included in a block and still fail, meaning it consumed gas but the contract logic reverted partway through. This is common when a swap's price moves past your slippage tolerance, or when a token requires an approval that was never granted. If a transaction shows "Fail," no tokens moved as a result of it, even though gas was spent. See Why a Transaction Fails on Base for the common causes.
A "Success" status means the transaction's top-level call did not revert, but it does not by itself tell you what moved and where. For that, you need the logs.
What event logs are
Smart contracts can emit events during execution, and each event is recorded as a log entry in the receipt. Logs are how contracts leave a structured, machine-readable trail of what happened, separate from the transaction's plain success or fail status. A single transaction can emit many logs. A token swap, for example, typically emits at least two Transfer events (tokens moving out of your wallet and the swapped tokens moving in) plus a Swap event from the pool contract that handled the trade.
Each log entry has:
- Address: the contract that emitted the event.
- Topics: indexed pieces of data, where the first topic (topic0) identifies which event type it is.
- Data: the remaining, non-indexed event data.
You can view logs for any transaction on Basescan by opening the transaction page and selecting the "Logs" tab.
Reading a Transfer event
The ERC-20 standard defines a Transfer(address from, address to, uint256 value) event, and every standard token contract emits it whenever tokens move. Its topic0 is always the same fixed value, 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef, because it is the keccak256 hash of the event signature. Because this hash never changes, explorers and indexers use it to recognize a Transfer event regardless of which token contract emitted it.
On the Logs tab, Basescan decodes this automatically for well-known token contracts, showing you the sender, recipient, and amount in plain terms instead of raw hex. If you swapped Token A for Token B, you should see one Transfer log showing Token A leaving your address and going to the pool, and a second Transfer log showing Token B leaving the pool and arriving at your address. If either leg is missing, the swap did not happen the way you expected, regardless of what the status field says.
Reading a Swap event
Decentralized exchange pools emit their own event, typically named Swap, that records the amounts of each token that went in and out of the pool along with the resulting price. Because Simple Base Swap routes trades through Base DEX pools, checking this log alongside the Transfer logs confirms both that the trade executed and roughly what rate you received. For background on how the trade itself is priced, see How a Token Swap Works Under the Hood.
Why this is worth checking
Wallet apps and interfaces summarize transactions for convenience, but that summary is generated by software you did not write. The receipt and logs are generated by the network as part of consensus, so they cannot be faked or edited after the fact by any app, including this one. If a balance ever looks wrong after a swap, or a wallet's activity feed seems out of date, checking the raw logs on Basescan is the way to see the actual outcome rather than a cached summary.
A limitation worth knowing
Reading logs tells you what happened on-chain, but it will not tell you whether a token contract behaves honestly in general. A token can implement standard Transfer events and still contain unusual logic elsewhere, such as fees on transfer or transfer restrictions. For that kind of check, see How to Research a Token Before You Swap It. Event logs confirm what a specific transaction did, not what a contract might do differently next time.
Next time a transaction feels ambiguous, skip the wallet notification and go straight to the receipt. It is the same record every block explorer, indexer, and other wallet is reading from, which makes it the most reliable way to confirm what actually happened.