Can I prove a swap happened if the site I used no longer exists

07 September 2026

Yes, you can prove a swap happened even if the site you used is gone, provided you saved the on-chain transaction record. The blockchain itself is the permanent record, not the website that wrapped it in a user interface.

Here is why that matters. When you use a decentralized exchange or any swap service that settles on Arbitrum, the actual exchange of tokens happens inside a smart contract. That contract executes on the Arbitrum blockchain, and its action is recorded as a transaction. The website you visited was just a front end - a convenient tool to build, sign, and submit that transaction. If the site goes offline, the chain of blocks remains. The transaction hash, the block number, the wallet addresses, and the amounts are all still there, readable by any block explorer.

The problem is finding that transaction if you did not save its hash. Without a record of the transaction ID, you have to reconstruct it from your wallet history. If you still control the wallet you used, you can look up its transaction list on a block explorer. That list shows every swap you made, including the contract interaction. The explorer will display the tokens sent and received, the timestamp, and the contract address. That is sufficient proof for most tax authorities or personal audits.

But there are limits. The swap happened on Arbitrum, not on the main Ethereum chain. Arbitrum is a rollup, and its transaction data is eventually posted to Ethereum. That means the record is not quite as directly accessible as a mainnet transaction, but it is still verifiable through Arbitrum-specific explorers. The parent page on Arbitrum swap receipts and tax records explains how to navigate those explorers and what data to extract.

What you cannot prove is the exact exchange rate the site offered you, or any fees the site added on top of the on-chain gas cost. The blockchain records the net tokens out of your wallet and the net tokens in. Any slippage, spread, or extra commission the site took is baked into those numbers. If you need to show the rate you were quoted versus the rate you got, you need a screenshot of the swap confirmation screen. That is covered in the sibling page about what details to screenshot before you close that screen.

If you lost the transaction hash and your wallet history is empty because you cleared it or used a temporary wallet, then you probably cannot prove the swap. The blockchain does not know who you are. It only knows which address signed the transaction. If you cannot link yourself to that address, the record is anonymous. That is why saving the hash, the wallet address, and the date is the only reliable backup.

The situation gets harder if the swap involved a token that has since been delisted or a contract that was exploited later. The transaction will still show in the explorer, but the token’s price or value at the time may be difficult to reconstruct from external data sources. If the token no longer trades on any major index, you may have to use the historical price from a decentralized oracle or a snapshot taken at the time of the swap. That is not the blockchain’s fault; it is a data problem.

A final caution. Some swap sites route trades through aggregators or multiple contracts. The transaction you signed might go to a router contract, which then splits the trade across several pools. In that case, the on-chain record shows the router interaction, not the individual pool swaps. You can still trace the internal calls if the explorer supports it, but it requires more work. Save the swap summary page if the site provided one. That summary is not on-chain, but it helps you interpret the on-chain data later.

If the site no longer exists, you are left with whatever you saved before it disappeared. That is why the page on Arbitrum swap receipts and tax records is the next thing to read. It walks through exactly which records survive a site’s death and which do not.

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