Key points:
- A bridge locks your coins on one chain and gives you the same value on another chain.
- Your real coins never travel. You get a wrapped copy, or a fresh native mint, on the other side.
- Bridges hold huge piles of locked coins, so hackers target them. Test with a small amount first.
Why chains cannot talk to each other
Every blockchain keeps its own record book. Ethereum tracks its own balances, Solana tracks its own, and Arbitrum tracks its own. None of them can read another chain's book: each chain trusts only its own rules.
So when you want to use ETH on Arbitrum, where fees are far lower, you hit a wall: you cannot send ETH to an Arbitrum address like any other wallet. A bridge links the two books.
How a bridge moves your coins
Most bridges use lock-and-mint. To move 100 USDC from Ethereum to Arbitrum, you send the 100 USDC to the bridge's smart contract on Ethereum, and the bridge locks it there. Then it mints 100 wrapped USDC for you on Arbitrum.
The wrapped token is an IOU backed by the locked coins. To go back, burn the wrapped USDC on Arbitrum, and the bridge unlocks your original 100 USDC on Ethereum. The coin itself never crossed anything. A second design skips the wrapper: Circle, the company behind USDC, burns your USDC on one chain and mints fresh, native USDC on the other.
Three bridge designs, and what changes for you
The design decides how fast your coins arrive and what can go wrong.
| Design | How it works | What you get | Speed |
|---|---|---|---|
| Lock-and-mint | Locks coins on one chain, mints a copy on the other | A wrapped token | Minutes |
| Liquidity and intent-based | A relayer pays you from a pool | The real coin, fast | Seconds |
| Native burn-and-mint | Burns on one chain, mints native coins on the other | Native coins, no wrapper | Minutes |
Lock-and-mint is the oldest design, used by the official Arbitrum Bridge and by Wormhole. Liquidity bridges like Across and Relay use a relayer who fronts the money on the destination chain, so your coins often arrive in seconds. Message bridges like LayerZero pass data between chains, and apps such as Stargate sit on top of them.
Read also: What Is a Layer 2 in Crypto? Ethereum's Fast Lane Explained
What bridging costs, and where the money goes
Bridging is never free: you pay the gas fee on the chain you leave, plus a fee to the bridge itself. Moving coins off Ethereum mainnet costs more than moving them between two cheap chains, because Ethereum gas is the expensive part.
A deposit from Ethereum to Arbitrum through the official bridge takes about 15 to 30 minutes. The trip back takes far longer: a standard withdrawal takes 7 to 8 days, because optimistic rollups wait out a challenge period first.
One cost catches beginners out: after your coins land on the new chain, you need that chain's own gas coin to do anything with them. Bridge USDC to Arbitrum without any ETH on Arbitrum, and your USDC sits stuck until you get some.
The risk most beginners miss
People treat bridging like a bank transfer, and it is not. A bank transfer moves numbers inside one system, while a bridge holds your real coins as collateral and hands you a copy, so the bridge itself becomes the target.
The Ronin bridge hack in March 2022 is the clearest warning: attackers stole about $625 million in ETH and USDC from the bridge that served the Axie Infinity game. It is still the biggest bridge hack on record. The figure comes from reports at the time, not from an audit, so treat it as a strong signal, not an exact count.
My own read is simple: a bridge is a road, not a parking spot. Move what you need, use it, and do not leave money sitting in a wrapped token because the trip back felt like a chore.
Bridge your first coins in 7 steps
- Pick the route first. For a first move, use the official bridge of the chain you are going to, such as the Arbitrum Bridge.
- Check the web address letter by letter. Fake bridge sites are a common phishing trick.
- Connect your wallet and pick the source chain, the destination chain, and the token.
- Read the quote first: the fee, the amount you will receive, and the time it will take.
- Send a small test amount first, about $10, and wait until it lands.
- Check the destination wallet: the coins arrived, and you hold some of the destination chain's gas coin.
- Only then send the rest, and keep the transaction hash until it lands.
FAQ
Do I lose my coins when I bridge? No. Your coins stay locked in the bridge's contract, and you get a wrapped copy or a fresh native mint on the other side.
How long does bridging take? Minutes on most routes, seconds on fast liquidity bridges. The trip back from Arbitrum to Ethereum takes 7 to 8 days through the official bridge.
Can I bridge Bitcoin to Ethereum? Yes, through a bridge that locks your BTC and mints wrapped BTC on Ethereum. Your real BTC never leaves the Bitcoin chain.
Read also: What Is Crypto Swapping? A Simple Guide to DEXs
Before your first real bridge, write down three numbers: the fee quote, the amount you send, and the amount that lands. Bridge a small test amount first, and only send the rest once it arrives. If the numbers do not match the quote, stop and check the route.
About the author: Muhammad Irfan is the founder and editor of BitByLine. He writes crypto news and beginner guides in simple, everyday language, so readers without a finance background can follow along. Read more about the editor.
This post is for learning only. BitByLine only explains and teaches — this is not financial advice, and we never tell anyone to buy or sell crypto. Whether you buy or not is always your own decision and your own risk. Always do your own research first. Read our full Disclaimer.
Sources: CoinGabbar, Web3Wagmi, Bitcoiva, CoinArbitrageBot, Arbitrum.
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