What Is a Crypto Bridge, and Why Do They Get Hacked?

Blockchains cannot see each other. Bitcoin has no idea Ethereum exists, and neither can read the other’s records. So moving value between them requires something in the middle, and that something is called a bridge.

How it works

The usual arrangement: you deposit an asset into the bridge on the first network, where it is locked. The bridge then issues you an equivalent representation on the second network. To go back, you return the representation and the original is released.

The representation is not the original asset. It is a token that is supposed to be redeemable for it, and its value depends entirely on that promise holding.

Why they get attacked

To function, a bridge has to hold the locked assets somewhere — often an enormous quantity in a single contract. That concentration makes it one of the most valuable targets in crypto, and several of the largest thefts on record have been bridge exploits.

They are also technically difficult. A bridge has to correctly verify events on one chain in order to act on another, and the machinery that does this is complex and comparatively new. Complexity is where bugs live.

When a bridge is drained, the representations on the far side may become unbacked — still visible in wallets, no longer redeemable for anything.

What this means in practice

Beginners rarely need a bridge. If you want an asset on a particular network, buying it there directly through an exchange usually avoids the bridge entirely, and the exchange handles the movement internally.

If you do use one, prefer established bridges with a long operating history and public security audits, move small amounts, and do not leave value sitting in a bridged representation longer than you need to.

And be precise about networks. Bridging is one of the situations where sending to an address on the wrong network is easiest to do, and as ever that mistake cannot be undone.