> For the complete documentation index, see [llms.txt](https://openledger.gitbook.io/openledger/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://openledger.gitbook.io/openledger/bridging.md).

# Bridging

OpenLedger utilizes the OP Stack Standard Bridge, deployed by AltLayer, our Rollup-as-a-Service (RaaS) partner. This ensures secure, standardized interoperability with Ethereum and aligns with the broader OP Stack ecosystem.

### **Key Highlights**

* **Non-proprietary**: The OP Stack bridge architecture (Bedrock era) is open source, audited, and used across multiple OP Stack rollups. The [OptimismPortal](https://specs.optimism.io/fault-proof/stage-one/optimism-portal.html#overview), L1StandardBridge, L2StandardBridge, and CrossDomainMessenger are canonical components. These contracts are non-proprietary and reused by projects like Base, Mode, Zora, etc.<br>
* **Custom Gas Token Bridging:** OpenLedger uses the OPEN ERC-20 token (deployed on L1) as its native gas token on L2. On the testnet, OPEN tokens are locked in the[ OptimismPortal contract on Sepolia](https://sepolia.etherscan.io/address/0x2241bdE3a85BE011BC4685D54cfE9829b5D66A5E) before being bridged. These locked tokens are then minted on L2 as part of the standard OP Stack deposit flow. While [OptimismPortal](https://specs.optimism.io/experimental/custom-gas-token.html?utm_source=chatgpt.com#optimismportal) is traditionally used for ETH deposits, OpenLedger leverages it for secure bridging of the OPEN token without altering the canonical bridge architecture.<br>
* **Secure Token Transfers**: Token bridging follows the standard OP Stack mint-and-burn model. L1 tokens are escrowed via OptimismPortal, and OPEN is minted on L2 upon deposit finalization. On withdrawal, OPEN is burned on L2 and unlocked on L1.<br>
* **Full Compatibility**: OpenLedger remains fully compatible with the standard Ethereum tooling and wallet ecosystem, including MetaMask, Ledger, Hardhat, and viem — just like any other OP Stack rollup.<br>
* **Audits & Disclosure**: The canonical bridge contracts — including the Ethereum token, L2 representations, and the bridge itself — have undergone multiple audits by firms such as OpenZeppelin and Trail of Bits. OpenLedger inherits these security guarantees, as no custom modifications were made to the underlying bridge architecture.