Optimism is a Layer 2 Ethereum scaling solution developed by OP Labs, using Optimistic Rollup technology to process transactions off-chain and post the results to Ethereum for security. Launched on mainnet in 2021, Optimism is one of Ethereum’s most important L2s — not only for its own chain but because its open-source codebase, the OP Stack, has become the dominant framework for building new Ethereum L2 chains. Coinbase’s Base, Worldcoin’s World Chain, Zora, Mode, and many others are all built on the OP Stack, forming the Superchain — an interoperable network of OP Stack chains sharing liquidity and security.
How Optimistic Rollups work: transactions are processed off-chain and assumed to be valid (“optimistically”) without immediate proof. Anyone can challenge a transaction during a 7-day fraud proof window. If no challenge is submitted, the transaction is finalised. This approach trades instant finality for simplicity — the 7-day withdrawal delay (moving funds from L2 back to Ethereum L1) is the main UX trade-off, mitigated by bridging protocols. The OP token governs the Optimism Collective, an innovative governance structure combining a Token House (OP holders) and Citizens’ House (reputation-based) to fund public goods. Optimism has committed to returning sequencer revenue to Ethereum public goods through retroactive funding.
Example: Coinbase builds Base using the OP Stack, instantly giving Optimism’s ecosystem access to Coinbase’s 100M+ users. Base’s success generates sequencer fees that flow back to the Optimism Collective treasury.
Learn more: Optimism — OP Stack Documentation
