Validity Proof
A cryptographic proof showing that off-chain transactions or computations were executed correctly without redoing them on-chain.
A validity proof is a small cryptographic proof that lets a blockchain verify that a batch of off-chain transactions or computations followed the rules, without checking every step itself. In layer 2 scaling, it is most commonly associated with zero-knowledge rollups, where many transactions are processed away from the main chain and then summarized on-chain with a proof. The proof shows that the new state, such as account balances after the batch, was produced correctly from the old state and the submitted transactions.
This matters because it reduces the amount of data and computation the base blockchain must handle, helping lower costs and increase throughput while still relying on the base chain for security. A practical comparison is a teacher checking a final answer plus a rigorous proof, rather than recalculating every line of work. If the validity proof verifies, the chain can accept the batch; if it does not, the batch is rejected. This differs from fraud proofs, which usually assume data is valid unless someone challenges it.
Other terms in Layer 2 & Scaling
Data Availability
The assurance that the transaction data needed to verify a blockchain or layer 2 network can be accessed by anyone who needs it.
Fraud Proof
A fraud proof is evidence submitted to a blockchain to show that a proposed transaction result or rollup state is invalid.
Layer 2
A Layer 2 is a secondary network or protocol built on top of a blockchain to process transactions faster and cheaper while relying on the main chain for security.
Layer 3
A Layer 3 is an application-specific blockchain layer built on top of a Layer 2 to add customization, scalability, or specialized features.