Sidechains, Bridges & Other Paths

A sidechain is its own independent blockchain, connected to a main chain via a bridge - but running its own consensus and its own validators. That's the crucial difference from a rollup: a sidechain does not inherit the main chain's security, no matter how closely it's associated with it.

Sidechains can be fast and cheap precisely because they aren't constrained by posting proofs back to a Layer 1. The cost is that you're trusting the sidechain's own validator set, separately from whatever chain it's connected to.

A state channel lets a small group of participants transact directly with each other off-chain, as many times as they like, and only settle the final outcome on the base layer once. It's fast and cheap for that narrow use case, but only really works for participants known in advance.

Sharding takes a different angle: instead of adding a layer on top, it splits the base layer itself into multiple parallel shards that each handle a portion of the network's data and transactions, then coordinates between them.

Moving an asset from one chain to another almost always goes through a bridge: tokens get locked (or burned) on the origin chain, and an equivalent representation is minted on the destination chain. Bridges are what let a single asset feel usable across many chains and Layer 2s.

They're also one of the most attacked parts of the entire ecosystem. A bridge concentrates a large pool of locked assets behind whatever validates the lock-and-mint process - smart-contract bugs or a compromised validator set there can be catastrophic, and unlike a rollup, a bridge to a separate chain doesn't get L1-level security for free.