How cross-chain USDT swaps work

Why a transfer can't cross chains

Each blockchain keeps its own ledger. USDT on TRON is a balance in a token contract on TRON; USDT on BNB Smart Chain is a balance in a different contract, on a different chain. A transfer updates one ledger, so it can only move tokens between addresses on that same chain. The other chain never hears about it. The seven networks compared covers how they differ.

So moving USDT “across” always takes two things: your USDT leaves you on chain A, and USDT reaches you on chain B. The options below differ in who sits in the middle and what you have to do.

Option 1: through an exchange

Deposit USDT on the network you have, then withdraw it on the network you need. The exchange credits your deposit to its internal records and pays the withdrawal from its own funds on the other network.

• You need an account at the exchange, usually with KYC.
• You pay its withdrawal fee, which differs by network. Your wallet also pays the network fee to send the deposit.
• The deposit is credited after the exchange's required number of confirmations, and a withdrawal can be held for review.
• Simple if you already have an account and the exchange supports both networks.

Option 2: through a bridge

A bridge is a set of smart contracts on both chains. You connect a wallet, approve the token and deposit it into the bridge on chain A, and the bridge pays out matching tokens on chain B. Depending on the design, it either pays out from a pool it holds on the other chain, or locks or burns your tokens on one side and mints new ones on the other.

• You need a self-custody wallet holding the tokens, plus the gas coin of the chain you leave, to pay for the approval and the deposit.
• Fewer bridges support TRON than the 0x networks, so check before you start.
• USDT0, a cross-chain version of USDT, moves between the chains it covers by burning on one and minting on the other. Arbitrum and Polygon are among them; its own site has the current list.
• Bridge contracts hold large amounts of tokens and have been hacked before. Use a well-known bridge, and check that you're on its real website.

Option 3: a swap service, which is how Flipperr works

A swap service takes your tokens on one chain and sends tokens on the other, with no wallet connection. Flipperr's swaps are carried out by our liquidity partner. Step by step:

1. You pick the route and the amount, and paste the address that should receive. The form shows an estimate with every fee already in it.
2. You get a one-time deposit address, an order ID and a window to send: 10 minutes for USDT or USDC, 45 for a coin.
3. You send from any exchange or wallet that supports the network. The order page moves through its stages: Awaiting deposit, Confirming (the deposit has been seen and is waiting for network confirmations), Exchanging, Sending to you, and Completed.
4. The payout is a separate transaction on the chain you receive on. Once the swap completes, the order page links to it on that chain's explorer. How to read it.

Nothing crosses between the chains: there's one transaction on the chain you send from and another on the chain you receive on. Three things are worth knowing before you use a service like this:

• The rate floats. The estimate follows the market until your deposit arrives, so the final amount can differ a little from what you saw.
• It's custodial while it runs. Between your deposit and the payout, your tokens are with our liquidity partner, not in your wallet. It can pause a swap it flags as risky and ask you to verify, under its own AML policy. Our terms and risk and AML policy explain more.
• It usually takes a few minutes. Busy networks can slow it down, and the order page shows each stage as it happens.

Which one to use

• Already have an exchange account that supports both networks? Deposit and withdraw, and pay its withdrawal fee.
• Tokens in a self-custody wallet, with gas, between chains a bridge supports? A bridge keeps an exchange out of it, though you rely on the bridge's contracts.
• No wallet connection, or moving off TRON? A swap service. Compare the “You get” amount with what the other options would leave you.

Where cross-chain moves go wrong

• The wrong network when you send. A 0x deposit address is valid on every 0x network, but only the one shown is part of the swap. If it's already happened.
• The wrong token: TRX, BNB or USDC sent where USDT was expected, or the other way round.
• Sending after the window closes. A Flipperr order expires if no deposit arrives within its window (10 minutes for USDT or USDC, 45 for a coin); don't send to its address after that, start a new swap.
• A different amount from the one on the order. Depending on the route, the swap is recalculated for what arrives or goes on hold until support sorts it out.
• The exchange's fee coming out of the amount. Some exchanges take their withdrawal fee from the amount you type, so less arrives than you entered, and the swap can go on hold. Check whether the exchange shows the amount before or after its fee, and add the fee on top if it comes out of the amount.
• A receiving address for the wrong network. Copy it from a deposit page with the right network selected, or from a wallet set to that network.