What Is Off-Chain Computation?

On a blockchain, every computation is repeated by all nodes in the network, so it is expensive and limited. On Ethereum, performing a complex computation inside a smart contract leads to high gas fees, and some operations do not fit within the block gas limit. In off-chain computation, the heavy work is done outside; the chain only verifies and records the result.

Different methods are used to make the result trustworthy. In systems based on zero-knowledge proofs, the party performing the computation produces a short proof showing that the result is correct, and the smart contract verifies this proof at low cost; ZK-Rollups and ZK coprocessors use this model. In optimistic systems, the result is assumed correct but can be disputed for a set period. In oracle networks, multiple independent nodes perform the computation and the results are combined by consensus. Hardware-based solutions such as trusted execution environments (TEEs) are also used.

Each method carries different trust assumptions: ZK proofs provide mathematical assurance but are costly to produce; optimistic systems require trusting at least one honest watcher, oracle networks require trusting the majority of nodes, and TEEs require trusting the hardware manufacturer. In structures where the computation is posted to the chain without verification, the user has to trust the party performing the computation.