How Crypto Bridges Work, and Their Risks

Updated 2026-10-29

Short answer: coins can't really leave their own blockchain. A bridge locks your tokens on one chain and gives you a stand-in token on the other. The stand-in is only as good as the bridge holding the originals. Use the chain's official bridge or a long-established one, send a small test first, and remember that an exchange can often do the same job more simply.

How a bridge works

Each blockchain only knows about itself. So when you "move" USDC from Ethereum to Base, or XRP onto Flare, something like this happens:

You send your tokens to the bridge on the first chain, where they're locked (or burned).
The bridge confirms that happened.
On the second chain, it creates a matching token for you (or releases one from its own supply).

Going back reverses it: the stand-in is burned, and the originals are released.

Some bridges are run by the chain itself (the "official" or "native" bridge, for example the ones for Arbitrum, Optimism and Base). Others are separate companies or protocols that connect many chains. Some tokens are issued directly on several chains by their maker (Circle does this for USDC), so the bridge doesn't hold them at all.

On Flare, FAssets bring XRP over as FXRP, backed by real XRP and extra collateral. See what FXRP is.

The risks

The bridge holds everyone's originals. That makes bridges a prime target. Some of the largest hacks in crypto were bridges: Ronin (2022, over $600 million), Wormhole (2022, about $320 million) and Nomad (2022, about $190 million). When a bridge is drained, its stand-in tokens can lose most of their value.
Fake bridge sites. Scam copies of popular bridges are bought as search ads and steal what you send. Open bridges from a bookmark or the chain's official site.
The wrong token on arrival. The same name ("USDC") can be several different tokens on one chain, from different bridges. Apps and exchanges may accept only one of them.
Waiting. Some withdrawals take days. Moving from an Ethereum layer 2 back to Ethereum through the official bridge usually takes about seven days.
No coins for fees. Arriving on a new chain with tokens but none of its own coin (ETH on Base, FLR on Flare) means you can't move them until you get some.
Approvals left behind. Bridging usually asks you to approve the bridge to spend your token. Check and revoke it afterwards: see how to check and revoke token approvals.

Bridging carefully

Ask whether you need a bridge at all. Many exchanges let you deposit on one network and withdraw on another. For a beginner, that is often simpler, if the exchange supports both networks.
Prefer the official bridge for the chain, or one that has been widely used for years.
Open it from a bookmark or the chain's official website, never from a search ad or a link in a message.
Send a small test first and wait until it arrives.
Check what you'll receive: which token, from which issuer, and that the app or exchange you plan to use accepts it.
Have a little of the new chain's coin for fees, or use a bridge that provides some.
Read the transaction before you sign it. See how to read a transaction before you sign.
Revoke the bridge's approval when you're done.

Do this

Bridge only when you need to, and consider your exchange first.
Use official or long-established bridges, opened from a bookmark.
Test with a small amount and check the token you receive.
Keep a little of the destination chain's coin for fees.
Don't leave large amounts in bridged tokens longer than you need to.