| [`L1CrossDomainMessenger`](../../specs/messengers.md) | [`ResolvedDelegateProxy`](./contracts/legacy/ResolvedDelegateProxy.sol) | High-level interface for sending messages to and receiving messages from Optimism |
| [`L1StandardBridge`](../../specs/bridges.md) | [`L1ChugSplashProxy`](./contracts/legacy/L1ChugSplashProxy.sol) | Standardized system for transfering ERC20 tokens to/from Optimism |
| [`L1StandardBridge`](../../specs/bridges.md) | [`L1ChugSplashProxy`](./contracts/legacy/L1ChugSplashProxy.sol) | Standardized system for transferring ERC20 tokens to/from Optimism |
| [`L2OutputOracle`](../../specs/proposals.md#l2-output-oracle-smart-contract) | [`Proxy`](./contracts/universal/Proxy.sol) | Stores commitments to the state of Optimism which can be used by contracts on L1 to access L2 state |
| [`OptimismMintableERC20Factory`](../../specs/predeploys.md#optimismmintableerc20factory) | [`Proxy`](./contracts/universal/Proxy.sol) | Deploys standard `OptimismMintableERC20` tokens that are compatible with either `StandardBridge` |