How to check a swap transaction on a phone browser before it finalizes

07 September 2026

Before you send a swap, you must read the transaction details on the phone browser where the exchange is open. The wallet app will show you a summary, but the full data lives on the exchange page.

Here is why this matters. Mobile wallets truncate swap details. They show you "Send 0.1 ETH" and "Receive 25 USDC" but hide the slippage tolerance, the contract address, and the exact path the tokens will travel. A browser page on the same phone displays all of that. You must check it.

The flow is simple. You initiate the swap on the exchange website in your phone browser. The site asks you to connect your wallet. You connect. You enter the amount. The site generates a preview. On that preview page, before you tap "Swap" or "Confirm," the browser shows:

• The token you send and the token you receive, with their contract addresses. Tap the token name to see the address. Scammers swap the token for a fake one here.
• The exchange rate, including the slippage percentage. A swap set to 5% slippage can cost you far more than a network fee.
• The network fee estimate, shown in the native token of that chain. A fee of $50 on a $20 swap is a red flag.
• The "Minimum received" line. That number is what you will actually get if the market moves. If it is zero, the swap has no protection.
• A "Transaction data" or "Hex data" link. Tapping it shows the raw instructions the contract will execute. Most people cannot read hex, but you can check that the recipient address listed there matches the destination you intended.

You must scroll. Mobile browsers hide the bottom of a swap preview behind the keyboard or the address bar. Pull the page down. If you cannot see "Minimum received," the swap is incomplete.

Now, the trick: before you tap confirm in your wallet, switch back to the browser. The wallet will pop up with a "Sign" or "Confirm" button. Do not press it yet. Go back to the browser tab. Read the preview again. Some wallets update the preview after the wallet connects, changing the rate. If the rate dropped, cancel and start over.

The wallet app will also show a transaction request. On that screen, look for a "Details" or "Data" tab. Tap it. Compare the contract address shown there with the one on the browser. They must match. If they differ, the wallet is about to sign a different swap than what the browser shows. Deny the transaction.

Do this check on a phone with a data connection. If the phone loses signal after you read the preview but before you confirm, the swap may still execute. The transaction was signed, not canceled. This is covered in the sibling page "What happens if my phone loses signal right after I confirm a swap."

A common mistake: people read the preview once, then switch to the wallet and confirm without checking again. The market can shift in those seconds. So can the swap contract. Read the browser preview, switch to the wallet, read the wallet details, switch back to the browser, read the preview again. Then confirm.

If the browser shows a warning about high slippage or a suspicious contract, do not proceed. Close the page. Start a new swap. The hub page "Mobile wallet swap mistakes to avoid" lists other errors that happen on phones, like approving too many tokens or rushing through the network selection.

Checking the transaction on the phone browser before finalizing takes thirty seconds. Skipping it can cost the whole swap. Read the preview, read it again, and only then tap confirm.

Back to mining