Before approving an Ethereum swap, verify the site and connected wallet, check both token contract addresses, review the quote and fees, understand the minimum-output or slippage setting, and inspect any separate token approval. Then compare the wallet prompt with what you intended to do. A valid signature does not guarantee a favorable result: the quote can change, a trade can execute at a price you would not have chosen, and an on-chain transaction is generally irreversible.
Before you sign: the checklist
- Confirm the site and wallet. Open the exchange from a bookmark or another trusted source, check the domain carefully, and make sure the connected wallet is the one you intend to use. Do not follow unsolicited support links or disclose a recovery phrase.
- Verify both token contracts. Match the full address for each token against information from its issuer. A familiar name or ticker is not proof that a token is genuine.
- Check the trade details. Confirm the input token and amount, output token, estimated output, exchange rate, fees, and any price-impact warning.
- Understand the output floor. Read the slippage tolerance and minimum amount received, if shown. Know how much less than the estimate you are willing to accept before signing.
- Review any separate approval. Check which address is allowed to spend your token and how much permission you are granting. An approval is distinct from the swap.
- Read the wallet prompt. Confirm that its decoded details match the action you expect. Do not sign raw, unexplained, contradictory, or unrelated requests.
- Stop for severe price impact or an unexpected quote change. Reduce the trade size, compare routes, or abandon the swap rather than overriding a warning you do not understand.
- Check the transaction after signing. Use a trusted block explorer to inspect whether it succeeded and what happened. A failed transaction can still cost gas.
These checks address different risks. A genuine site can still present a poor quote; a genuine token can still be illiquid; and a wallet can faithfully sign a transaction that does not achieve your economic goal. Ethereum.org’s security guidance covers phishing, transaction review, and recovery-phrase safety, while its token-swap guide advises reviewing the exchange rate and fees before confirming.
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1. Is this the right site and wallet?
Start before connecting your wallet. Check the domain character by character, including spelling and the ending of the address. A fraudulent site can copy a legitimate exchange’s appearance, and an imitation interface may be designed to prompt a wallet action that looks routine. Ethereum.org warns about phishing sites that impersonate legitimate services.
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Use a known bookmark or reach the service through a trusted source rather than an unsolicited message, search advertisement, or purported support conversation. A support agent does not need your seed phrase or private key to help with a swap. Anyone who asks you to reveal either should be treated as a threat to the wallet, not as a legitimate step in the trade.
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Once the site is open, check the connected account and network shown by the interface and wallet. If the account is not the one you mean to use, disconnect or switch accounts before proceeding. Do not assume that a familiar wallet address shown on the website proves that the site itself is genuine: site identity and wallet identity are separate checks.
2. How do I verify the tokens?
Check the full contract address for both the token you are selling and the one you expect to receive. Token names and ticker symbols are not unique; another token can copy them. Compare the address displayed by the swap interface against the token issuer’s official information. A reputable block explorer or exchange listing can provide a secondary clue, but neither is definitive proof that a token is authentic.
Pay particular attention when a token appears through a search result, a link, or a recently added listing. Do not select a result solely because its name, logo, or ticker matches what you expect. A small address difference can identify a different contract altogether. Ethereum.org’s scam-token guide explains why contract addresses matter and discusses liquidity and other indicators. Those indicators can help inform a decision, but they do not replace checking the issuer’s address.
If you cannot establish that the contract is the one you intended, stop. Do not try to compensate for uncertainty by swapping a small amount first: a test trade does not establish that a token is genuine, that a route is safe, or that a later transaction will have the same terms.
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3. Does the quote match the trade I intend to make?
Read the trade from input to output. Confirm the asset you are giving up, the exact amount, the asset you will receive, and the estimated output. Check the exchange rate and every fee the interface shows, including the network cost presented by the wallet. A displayed output estimate is a quote, not a promise of what will arrive.
Price impact is the effect the trade size has on the pool price. A large trade relative to available liquidity can move the price substantially, reducing the amount received. A warning about high price impact is a reason to pause, not an obstacle to click through. Consider reducing the size, comparing available routes at the same time and for the same input amount, or not trading.
When comparing routes or interfaces, use the same input amount and compare the values that affect the result:
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- Price impact: check the impact for your intended trade size; a route that looks attractive for a small trade may be poor for a larger one.
- Slippage and minimum output: make sure you can identify the tolerated movement and the output floor that will cause execution to fail rather than settle below that floor.
- Approval: check the spender and token amount the route requires you to authorize.
- Wallet-readable details and network cost: consider whether the wallet makes the requested action understandable and what gas cost it displays.
Quotes can change as market and pool state change, so compare routes at roughly the same time. A new quote is not automatically safer or better: read its details again rather than relying on the earlier screen.
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4. What is slippage?
Slippage is the difference between the expected exchange rate and the rate at which the swap actually executes. Ethereum.org describes it as “the difference between your expected exchange rate and the actual rate” in its guide to swapping tokens. The difference can arise because execution happens against pool state that may have changed since the quote was generated.
A slippage tolerance sets how much movement the swap will accept under the interface’s rules. If the price moves beyond the accepted limit, the transaction may fail rather than execute. If the tolerance is loose, the trade may be allowed to complete for materially less than the quote. Read the minimum amount received when the interface displays one: that figure makes the tolerated downside more concrete than a percentage alone.
Do not choose a setting simply because the interface suggests it, or raise it just to make a swap go through. If the quote changes unexpectedly, the setting is unfamiliar, or you cannot tell what output is protected, pause and investigate. The right choice depends on the trade and its route; the source material does not establish one universal safe tolerance for every swap.
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5. Is a token approval separate from the swap?
Often, an ERC-20 token must first be approved for a spender to transfer it on your behalf. That permission is called an allowance. The approval and the swap are separate actions: approving a token does not itself perform the trade, and a later swap may require a separate transaction.
For an approval prompt, check the token being authorized, the spender address, and the amount. Make sure the spender is consistent with the route you chose; do not assume that a plausible name in the interface is enough. If the wallet or interface lets you set an amount, prefer the smallest usable allowance instead of granting unlimited access by default. A broad allowance can leave tokens exposed if the spender or interface is malicious or later compromised. Ethereum.org’s security guidance and the Ethereum Foundation’s discussion of blind signing and transaction uncertainty describe why transaction review and spending limits matter.
If you do not understand why an approval is being requested, which address will receive it, or how much it covers, do not sign it just to reach the swap screen. Recheck the route and prompt first. Approval permission is not the same as a guarantee that a swap will happen, nor does it guarantee that the resulting trade will be favorable.
6. What should the wallet prompt show?
Before signing, compare the wallet’s transaction details with the action shown by the exchange. Check the contract or recipient information the wallet exposes, the token and amount where available, the network, and the expected spender for an approval. The exact presentation differs across wallets and applications; do not assume that every prompt will translate contract behavior into plain language.
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Stop if the wallet shows raw data you cannot interpret, an unexplained recipient or contract, a request for unrelated permissions, or details that contradict the swap interface. A website’s summary is not a substitute for the wallet prompt: the wallet is asking you to authorize the transaction that will actually be submitted.
The Ethereum Foundation’s clear-signing announcement describes work toward human-readable, structured transaction descriptions and review on a separate device. Clear-signing support is not universal, and no particular wallet display should be assumed to make every swap understandable. A hardware wallet is optional, not a prerequisite; a separate screen does not by itself establish that a token is genuine or that the trade’s economics are acceptable.
7. Why a valid signature can still produce a bad swap
Signing confirms authorization; it does not guarantee that the transaction will deliver the result you wanted. It is useful to distinguish two kinds of mismatch. An intent mismatch is when the transaction shown is not the one the user thought they were approving. An outcome mismatch is when the authorized transaction executes, but the result falls outside the user’s economic goal.
The Ethereum Foundation’s October 5, 2026 article on native transaction assertions illustrates the second risk with a specific Aave/CoW collateral-swap case. Its account says a 99.9 percent price-impact warning appeared; the Foundation describes about $50.4 million in aEthUSDT value and tokens received worth about $36,000. These are approximate figures from that one case, not typical swap results or a general estimate of swap losses.
The article describes native transaction assertions as research, not a general protection already available in Ethereum wallets. The practical lesson is to evaluate the minimum output and price impact before signing, rather than treating a valid signature or successful execution as proof that the result was acceptable. As ethereum.org puts it, “A transaction sent on Ethereum is irreversible.”
8. What to do after signing
- Find the transaction hash. Open the transaction details from the wallet or swap interface and copy the hash, rather than following an unsolicited link claiming to show its status.
- Open a trusted block explorer independently. Search for the hash and check whether the transaction is pending, succeeded, or failed.
- Inspect the result. For a completed swap, verify the token transfers and amounts shown against what you expected. For a failed transaction, note that gas may still have been spent.
- Do not repeat a failed or confusing action blindly. Recheck the quote, approval, network, and wallet prompt before attempting another transaction.
Ethereum transactions are ordinarily irreversible once completed. An explorer can help you understand what happened; it cannot reverse a completed swap or guarantee recovery of funds. If the transaction appears to involve an approval you did not intend, avoid further use of the affected route while you establish what permission was granted.
A final pre-sign decision
Proceed only when you can explain, in plain language, which token and amount you are sending, which token you expect to receive, what the minimum acceptable output is, what fees and price impact are shown, and which spender—if any—you are authorizing. If any of those details is missing or inconsistent between the site and wallet, do not sign yet. Cancel and verify rather than relying on the transaction’s appearance, a familiar token symbol, or the fact that the wallet produced a confirmation prompt.
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