Bridges & Portals

wstGBP bridges to L2s and sidechains using each chain’s own canonical bridge. Every L2 balance is a canonical-bridge representation of the L1 token rather than an OFT, xERC20, or omnichain deployment. That means five different architectures: the OP Stack Standard Bridge (Base, OP Mainnet, Unichain, Ink, Celo, MegaETH), the Arbitrum Nitro gateway (Arbitrum One, Robinhood Chain), the Polygon PoS bridge, the Gnosis OmniBridge, and the zkSync Elastic Network shared bridge (zkSync Era). The L1 token is always the source of truth.

L1 token on Ethereum mainnet (chainId 1)

Live deployments

RPC endpoints & explorers

Public, keyless RPC endpoints and block explorers for every chain wstGBP is deployed on. Chains marked (Blockscout) have no Etherscan-family explorer.

OP Stack chains

Six deployments (Base, OP Mainnet, Unichain, Ink, Celo, MegaETH) share the OP Stack Standard Bridge architecture. The L2 predeploys are identical on every chain; only the L1 contract set differs.

• Deposit (L1 to L2): approve the chain’s L1StandardBridge for wstGBP, then depositERC20(l1Token, l2Token, amount, minGasLimit = 200000, extraData = 0x). Use depositERC20To(..., to, ...) from a contract/Safe or to a different recipient (depositERC20 has an onlyEOA guard). Not payable; you pay L1 gas only. Arrives in minutes.
• Withdraw (L2 to L1): bridgeERC20To on the L2 bridge 0x4200...0010, then finalize on L1 after the challenge period.

L1 bridge contracts per chain

Users interact with the L1StandardBridge; the OptimismPortal and L1CrossDomainMessenger come into play when proving and finalizing withdrawals.

Shared L2 predeploys

All six chains mint their wstGBP through the factory predeploy 0x4200...0012, except Base, which runs its own factory 0xF10122D428B4bc8A9d050D06a2037259b4c4B83B (v1.9.0). Base’s tooling and bridge UI expect tokens from that factory, which is why Base’s wstGBP address differs from the predeploy-factory chains.

Arbitrum Nitro chains

Two deployments use the Arbitrum Nitro canonical ERC-20 gateway. In both cases the L2 wstGBP is a StandardArbERC20, auto-deployed by the gateway on first deposit (no factory call, no predeploy), and l1Address() on the L2 token resolves back to L1 wstGBP.

The deposit flow is the same on both: approve the chain’s L1ERC20Gateway (not the router) for wstGBP, then L1GatewayRouter.outboundTransferCustomRefund(...), a payable call that needs L2 gas params (maxGas, gasPriceBid, maxSubmissionCost). Prefer the portal.arbitrum.io/bridge  UI or the Arbitrum SDK.

Arbitrum One (chainId 42161)

L2 wstGBP: 0x2c8CBe32da6feAECcF99eCeE2900556a17a529ED

Robinhood Chain (chainId 4663)

Robinhood Chain is an Arbitrum Orbit L2 that settles directly to Ethereum (Ethereum blobs for DA, ETH as native gas), not an L3 on Arbitrum One. It uses the same Nitro gateway architecture as Arbitrum One but with its own gateway/router set, so bridging runs directly between Ethereum L1 and Robinhood Chain.

Polygon PoS bridge (chainId 137)

L2 wstGBP 0x3319d8A0A7f742AAC63D586E7bb846a9ee8218Ab is a native PoS-bridge child ERC-20 (the L1 ERC20Predicate locks, the L2 ChildChainManager mints/burns; backed 1:1).

Deposit (L1 to L2): approve the ERC20Predicate, then RootChainManager.depositFor(user, wstGBP, abi.encode(amount)). Arrives in about 20-30 minutes via state sync. Withdraw (L2 to L1): withdraw(amount) on the child token to burn, wait for the next Heimdall checkpoint, then RootChainManager.exit(burnProof) on L1; the Portal UI assembles the proof.

Gnosis Chain OmniBridge / AMB (chainId 100)

L2 wstGBP 0x68115fFA8bF088289B80B1e17cD486B5752492aA is an ERC677 PermittableToken, auto-deployed by the Home mediator on first deposit (backed 1:1 by tokens locked on L1).

Deposit (L1 to Gnosis): approve the Foreign mediator, then relayTokens(wstGBP, receiver, amount). Arrives in about 5-15 minutes. Withdraw (Gnosis to L1): relayTokens(...) on the Home mediator (or ERC677 transferAndCall(homeMediator, amount, "")) to burn, wait for validator signatures, then submit the signed claim on L1. Gnosis-to-Ethereum messages are not auto-relayed, so the bridge UI (or you) must pay the L1 claim.

zkSync Era shared bridge (chainId 324)

zkSync Era is a ZK (validity) rollup on the ZK Stack. Its canonical bridge is the Elastic Network shared-bridge system: on L1, deposits enter through Bridgehub, which routes them via L1AssetRouter into L1NativeTokenVault; the L2AssetRouter / L2NativeTokenVault predeploys mirror them on L2. L2 wstGBP 0xa84340Bee7aAA2E9aB0Da89024a4c13144Eaf41d is a BridgedStandardERC20 beacon proxy, auto-deployed by the L2NativeTokenVault on first deposit. The L1 vault locks wstGBP and the L2 vault mints/burns, so L2 supply is backed 1:1 by tokens locked in the L1 vault. originToken() on the L2 token resolves back to L1 wstGBP.

Deposit (L1 to Era): Bridgehub.requestL2TransactionTwoBridges(...) with the L1AssetRouter as the second bridge, a payable call that needs L2 gas params (l2GasLimit, l2GasPerPubdataByteLimit) plus an ERC-20 approval for the vault. The Portal UI  assembles the call and the approval. Arrives in a few minutes. Withdraw (Era to L1): initiate on L2 (the Portal calls the L2AssetRouter to burn), wait for the batch to be proven and executed on L1 (Era applies an execution delay, about 24 hours in practice), then finalize on L1 via the L1Nullifier/L1AssetRouter. The Portal UI assembles and submits the L1 claim, so prefer the UI for the exit.