What Is Sidechain?
A sidechain is an independent blockchain that runs in parallel to a main chain (like Ethereum) and is connected through a two-way bridge that allows assets to move between them. Unlike Layer 2 solutions, sidechains have their own consensus mechanism and security model — they don't inherit security from the main chain.
How Sidechain Works
Sidechains offer customization: they can use different consensus mechanisms (PoS, PoA), different block times, different fee structures, and different execution environments while still interoperating with the main chain through the bridge. Polygon PoS (before its transition to a ZK solution) was the most prominent Ethereum sidechain, offering faster and cheaper transactions.
Why It Matters for Traders
The key difference between sidechains and L2s is the security model. L2s inherit the security of the L1 (if the L2 goes down, your funds are still safe on L1). Sidechains rely on their own validator set — if the sidechain consensus is compromised, funds on the sidechain are at risk. This distinction matters for risk assessment when bridging significant capital.
