Awesome Optimism Bridges

List of currently developed optimism bridges.

Optimism is an experimental tech and all bridges have some upgradeability patterns for now

DAI

BellwoodStudios/optimism-dai-bridge

Key contracts

• L1Gateway
• L1Escrow
• L2Gateway
• DAI
• L1GovernanceRelay & L2GovernanceRelay

Characteristics

• L2 DAI is separated from the bridge contracts
• On L1, funds are held in a shared escrow to make upgrades easy
• GovernanceRelay contract allows executing cross-chain governance spells
• Upgradeability fully controlled by the governance

SNX

Synthetixio/synthetix

Key contracts

• SynthetixBridgeToOptimism (L1)
• SynthetixBridgeToBase (L2)
• SynthetixBridgeEscrow (L1)

Characteristics

• L2 SNX is separated from the bridge contracts
• On L1, funds are held in a shared escrow to make upgrades easy
• Allows to save tokens accidentally sent to escrow

LINK

smartcontractkit/LinkToken (PR)

Key contracts

• OVM_L1ERC20Gateway
• OVM_L2ERC20Gateway
• OVM_EOACodeHashSet

Characteristics

• L2 LINK is separated from the bridge contracts
• Transparent upgradeable proxy pattern is used for upgradeability
• On L1, funds stored are locked in the token bridge proxy (not in the escrow)
• Prevents withdrawing funds to the contract addresses. Checking for this on Optimism is not trivial.

UniBridge

Original Optimism PR
Dedicated Repo

Key Contracts

• L1TokenBridge
• L2TokenBridge

Characteristics

• Deposit any ERC20 token in the L1 bridge to mint on L2, preventing new bridge contract for each token
• Each L1 ERC20 gets a generic ERC20 and ERC777 counterpart. It gets created when a new token is being bridged for the first time
• Supports ERC20 or ERC777 on L2, with simple converstion between the two
• L1 bridge can calculate the address of L2 tokens using Create2

Other

Token Standard

Optimism team come up with a Token Bridge Standard. Currently, it's still under discussion, and no bridges implement this interface.