# Bridge ERC-20 Tokens

MegaETH's canonical bridge supports ERC-20 token bridging via the OP Stack [Standard Bridge](https://docs.optimism.io/app-developers/guides/bridging/standard-bridge). Bridging locks tokens in the `L1StandardBridge` on Ethereum and mints a paired `OptimismMintableERC20` on MegaETH.

## Prerequisites

* [Foundry](https://getfoundry.sh/) installed (`forge` and `cast`)
* A wallet funded with ETH on both L1 (for deployment and bridging gas) and L2 (for registration gas)
* An ERC-20 contract ready to deploy, or an existing L1 token address

## Contract Addresses

{% tabs %}
{% tab title="Mainnet" %}

| Contract                     | Chain                        | Address                                      |
| ---------------------------- | ---------------------------- | -------------------------------------------- |
| L1StandardBridge             | Ethereum (chain 1)           | `0x0CA3A2FBC3D770b578223FBB6b062fa875a2eE75` |
| OptimismMintableERC20Factory | Ethereum (chain 1)           | `0xF875030B9464001fC0f964E47546b0AFEEbD7C61` |
| L2StandardBridge             | MegaETH Mainnet (chain 4326) | `0x4200000000000000000000000000000000000010` |
| OptimismMintableERC20Factory | MegaETH Mainnet (chain 4326) | `0x4200000000000000000000000000000000000012` |
| {% endtab %}                 |                              |                                              |

{% tab title="Testnet (Sepolia)" %}

| Contract                     | Chain                             | Address                                      |
| ---------------------------- | --------------------------------- | -------------------------------------------- |
| L1StandardBridge             | Ethereum Sepolia (chain 11155111) | `0x8033d50c753b3f19748f239ac8cf915b2888cd32` |
| OptimismMintableERC20Factory | Ethereum Sepolia (chain 11155111) | `0x11f008caa3083aa8a3b6f9f06f923e98a28fa286` |
| L2StandardBridge             | MegaETH Testnet (chain 6343)      | `0x4200000000000000000000000000000000000010` |
| OptimismMintableERC20Factory | MegaETH Testnet (chain 6343)      | `0x4200000000000000000000000000000000000012` |
| {% endtab %}                 |                                   |                                              |
| {% endtabs %}                |                                   |                                              |

## Steps

{% stepper %}
{% step %}

#### Deploy your ERC-20 on L1

Deploy your token contract on Ethereum (or Sepolia for testing). The example below uses a Foundry script; adapt it for your own token.

```bash
forge script script/Deploy.s.sol \
  --rpc-url $L1_RPC \
  --broadcast \
  --private-key $PRIVATE_KEY
```

Save the deployed token address — you will need it in the next step.
{% endstep %}

{% step %}

#### Register the L2 counterpart

Call `createOptimismMintableERC20` on the `OptimismMintableERC20Factory` **on MegaETH**. This deploys a bridgeable ERC-20 on L2 that is linked to your L1 token. Replace `"MyToken"` and `"MTK"` with your token's name and symbol.

```bash
cast send $L2_MINTABLE_FACTORY \
  "createOptimismMintableERC20(address,string,string)" \
  $L1_TOKEN "MyToken" "MTK" \
  --rpc-url $L2_RPC \
  --private-key $PRIVATE_KEY
```

The factory emits an `OptimismMintableERC20Created(address indexed localToken, address indexed remoteToken, address deployer)` event. Parse the `localToken` field from the receipt to get your L2 token address.

```bash
# Extract the L2 token address from the event logs
# topics[0] is keccak256("OptimismMintableERC20Created(address,address,address)")
# topics[1] is the L2 token address ABI-encoded as a 32-byte padded value; [26:] strips the leading zeros
cast receipt $TX_HASH --rpc-url $L2_RPC --json \
  | jq -r '.logs[] | select(.topics[0] == "0x52fe89dd5930f343d25650b62fd367bae47088bcddffd2a88350a6ecdd620cdb") | "0x" + .topics[1][26:]'
```

{% endstep %}

{% step %}

#### Approve the L1 bridge

Approve `L1StandardBridge` to spend the tokens you want to bridge. Set `$AMOUNT` in wei (e.g. `100000000000000000000` for 100 tokens with 18 decimals).

```bash
cast send $L1_TOKEN \
  "approve(address,uint256)" \
  $L1_BRIDGE $AMOUNT \
  --rpc-url $L1_RPC \
  --private-key $PRIVATE_KEY
```

{% endstep %}

{% step %}

#### Bridge tokens to MegaETH

Call `bridgeERC20` on `L1StandardBridge`. Pass both the L1 and L2 token addresses, the amount in wei, a minimum gas limit for L2 execution, and empty extra data.

```bash
cast send $L1_BRIDGE \
  "bridgeERC20(address,address,uint256,uint32,bytes)" \
  $L1_TOKEN \
  $L2_TOKEN \
  $AMOUNT \
  200000 \
  0x \
  --rpc-url $L1_RPC \
  --private-key $PRIVATE_KEY
```

`200000` is sufficient for most standard ERC-20 tokens. The bridge transaction locks tokens on L1 and relays a message to MegaETH to mint the equivalent amount on L2.
{% endstep %}

{% step %}

#### Verify the L2 balance

After the L1 transaction is finalized and relayed (\~1–2 minutes), check the balance on MegaETH.

```bash
cast call $L2_TOKEN \
  "balanceOf(address)(uint256)" \
  $(cast wallet address --private-key $PRIVATE_KEY) \
  --rpc-url $L2_RPC
```

{% hint style="info" %}
The deposit takes approximately 1–2 minutes to appear on MegaETH — one L1 block for finality, plus sequencer relay time. You can track the L1 transaction on [Etherscan](https://etherscan.io) (mainnet) or [Sepolia Etherscan](https://sepolia.etherscan.io) (testnet), and the L2 deposit on [MegaETH Blockscout](https://megaeth.blockscout.com) (mainnet) or the [testnet explorer](https://megaeth-testnet-v2.blockscout.com).
{% endhint %}
{% endstep %}
{% endstepper %}

## Withdrawals (L2 → L1)

Withdrawing tokens back to Ethereum requires initiating a withdrawal on L2 and then proving and finalizing it on L1 after the challenge period. This follows the standard OP Stack withdrawal flow — see the [OP Stack withdrawal guide](https://docs.optimism.io/app-developers/guides/bridging/standard-bridge#withdrawing-erc-20-tokens) for details.