Cross-chain · Base → Polygon

Swap WETH from Base to USDT on Polygon

Swap WETH from Base to USDT on Polygon. Wrapped ETH leaves Base, and Tether USDT arrives on Polygon chain 137.

The WETH you approve is 0x4200000000000000000000000000000000000006 on Base, chain 8453, on Basescan. Gas for the approval is ETH, not the wrapper itself. The USDT you receive is 0xc2132D05D31c914a87C6611C10748AEb04B58e8F, Tether, 6 decimals, on Polygonscan, chain 137. It is not Circle USDC and not USDC.e. Native gas uses 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE, which means ETH on Base and POL on Polygon. Neither native coin is the asset this quote exchanges.

Diagram for Swap WETH from Base to USDT on Polygon — WETH leaves Base. USDT is what can arrive on Polygon.

Selling wrapped ether into Tether

This is a change of asset, not a relocation of WETH. Polygon WETH, if you had wanted it, is 0x7ceB23fD6bC0adD59E62ac25578270cFf1b9f619. You will not see a credit there. You will see Tether, 6 decimals against WETH's 18, so the raw log integers are not comparable. Read the human amount on the quote, then the contract.

Circle would have been a different address

Native USDC on Polygon is 0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359. Bridged USDC.e is 0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174. A treasury that redeems at Circle cannot redeem this USDT at Circle. Tether's freeze list still applies on the destination contract. The bridge does not wash that status.

Two signatures people mix up

First you may approve WETH on Base. Later a Polygon app may ask to spend USDT, and that second request is paid in POL. You do not approve USDT in order to receive it. If the wallet is on the wrong chain, the spender address in the popup belongs to a different network. Check chain id 8453 for the input.

Receipts on two explorers

Basescan records WETH leaving. Polygonscan records USDT arriving. How to bridge assets between chains is the sequence, without a clock. Bring POL before you forward the dollars. If you hold native ETH instead of WETH, this page cannot see your balance. Decline a minimum you would not keep.

Legal

Risk disclosure

XAUConnect is a non-custodial swap aggregator. Digital assets are volatile and may lose value rapidly. Content on this page is educational and not investment advice. Verify every contract address on the official block explorer before approving a transaction.

Frequently asked questions

What is the best way to swap WETH from Base to USDT on Polygon?

The WETH you approve is 0x4200000000000000000000000000000000000006 on Base, chain 8453, on Basescan. Gas for the approval is ETH, not the wrapper itself.

Is the USDT here the same as Ethereum USDT?

The issuer is Tether and the decimals are 6, but the contract is 0xc2132D05D31c914a87C6611C10748AEb04B58e8F on Polygon, chain 137. Ethereum's contract is 0xdAC17F958D2ee523a2206206994597C13D831ec7. Check Polygonscan for the credit. A mainnet transfer will not move these tokens. The credit is on Polygonscan, chain 137, and it stays there until you use that network.

What if I have ETH on Base but no WETH?

This route spends 0x4200000000000000000000000000000000000006 only. Native ETH, 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE, pays gas and is not pulled as the input. Wrap on Base first, or use the route that sells native ETH for USDT. An empty WETH balance cannot be approved into a trade. Native ETH on Base can pay gas, but it is not this input.

Does arriving USDT include POL for fees?

No. USDT cannot pay gas on chain 137. POL is the native coin. The ETH you spent to approve WETH on Base stays on Base. Put POL on the Polygon account or the Tether balance is visible on Polygonscan and still immovable. POL has to be there first.

Live execution

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Open the swap page with this cross-chain route pre-selected, then connect your wallet on the source chain to quote and execute. You keep the keys.

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