Network profile: Optimism (OP Mainnet)

Network name
Optimism
Token
ETH
RPC
mainnet.optimism.io
Chain ID
10
Block explorer
OP Mainnet Explorer
Website
https://www.mainnet.optimism.io/

 

Formerly known as Optimism, OP Mainnet is a layer 2 (L2) rollup helping to scale Ethereum. Let's unpack how it works.

L2s are a type of blockchain closely linked to a corresponding layer 1 (L1), which, in this case, is Ethereum. Transactions are handled on the L2 itself, the execution layer, whilst data about these transactions is 'rolled up' into a condensed form and posted on L1, demanding significantly less computation than if all of the transactions were to be conducted entirely on L1. Their structure allows users access to high-capacity, fast and low-cost alternative to Ethereum mainnet whilst retaining the same fundamental mechanisms and features. Critically, L2s also inherit Ethereum's security and reliability. OP Mainnet's execution layer is called the OVM, or Optimism Virtual Machine.

OP Mainnet uses a system similar to Proof-of-Stake, in which entities running nodes help secure the network. In this case, they are called verifiers. Additionally, OP Mainnet requires a sequencer, responsible for collecting transactions from the L2, rolling them up, and posting them to L1 (Ethereum). The Optimism organization itself currently runs the sole sequencer on the network. 

As its name not-so-subtly hints, OP Mainnet belongs to the optimistic rollup category. Similarly to Arbitrum, one of the other major L2 platforms, OP Mainnet's protocols assume that all transactions are valid. This approach means that the network does not have to compute every transaction, significantly reducing congestion; instead, computation is only performed when the validity of the block is challenged.

This occurs in a process referred to as a fraud proof, which is where verifiers come in: when the state information or 'commitment' (i.e. the bundle of rolled-up transactions) is posted to Ethereum, a one-week 'challenge window' begins. Verifiers check state information and are responsible for initiating a fraud proof to resolve the issue. If proven right, verifiers are rewarded and the proposed commitment is replaced with a new one. This 'How Optimism Works' page is a good explainer if you want to find out more. 

Gas controls on OP Mainnet

When using OP Mainnet in MetaMask, you won't be able to manually adjust the amount of gas you pay using advanced gas controls, as you would on other networks. The feature is disabled instead. This is because it's not possible for users to specify gas limits when OP Mainnet submits the transaction to Ethereum. You can read more here.

 

Using OP Mainnet

How do I add OP Mainnet to MetaMask?

Adding a network is a straightforward process.

OP Mainnet is already configured as a popular network in MetaMask, so adding it is straightforward. Click 'Add network' and head to the 'Add popular networks' area (instructions here). From here, adding it to MetaMask should only take a few clicks or taps.

However, you can also manually input the network information above. For guidance, see here

Switching networks to OP Mainnet in MetaMask

When you add OP Mainnet as a new network, you will automatically switch to it.

However, if you need to switch back, follow the guidance below:

Extension Mobile

1. Select the drop-down arrow in the top left corner of the app. It will currently display the network you're connected to, such as 'Ethereum Mainnet', or any other you used last.

2. Scroll through the menu until you find the OP Mainnet network, then click on it to switch.

MetaMask Optimism network extension

What token do I need?
OP Mainnet uses Ether (ETH) as its native token, which means you'll need it to pay for transactions.
How do I bridge tokens onto OP Mainnet?

OP Mainnet has an official bridge that can be accessed here. Optimism have put together a step-by-step guide to using the bridge here.

You can also bridge to and from OP Mainnet using MetaMask Portfolio, here.

Another alternative is to use a direct on-ramp. These platforms allow you to purchase crypto with fiat currency (e.g. dollars, euros) and have the appropriate quantity of tokens deposited into your wallet. Again, MetaMask Portfolio's Buy section covers this need too. 

A list of supported on-ramps here, and you can also buy ETH on OP Mainnet directly in MetaMask Extension. Just make sure you have OP Mainnet selected as your current network and hit the 'Buy' button. Read more here.

Can I use my MetaMask address?
Yes. When you add OP Mainnet to MetaMask and use MetaMask on the network, you will be using your existing MetaMask public address.
Can I send tokens directly to and from OP Mainnet without bridging?

No. Always use the bridging methods described above to get your tokens onto OP Mainnet.

What kinds of tokens can be used on OP Mainnet?

OP Mainnet supports its native token, Ether (ETH), as well as ERC-20 tokens. You can move any token from Ethereum to OP Mainnet, provided it exists on both networks.

However, an ERC-20 token on Ethereum is not interchangeable with an ERC-20 token on OP Mainnet. They must be bridged first, and you must ensure the token is supported on OP Mainnet before trying to bridge it over.

This is because ERC-20 tokens are essentially created by smart contracts. If a token exists on Ethereum it will have a corresponding token (contract) address. This same logic applies to OP Mainnet: so if there is no contract address for a token on OP Mainnet, you cannot move that token to the network.

To get around this potential barrier, it's best to stick to using the Optimism bridge, which will only allow you to transfer the token if it is supported on OP Mainnet.

Since OP Mainnet is a L2 rather than a conventional EVM-compatible network (such as Binance Chain or Avalanche C-Chain), you cannot move tokens from these networks onto OP Mainnet, even if they have an ERC-20-equivalent standard (such as BEP-20). You must go via Ethereum mainnet.

 

Useful resources

Optimism docs: How Optimism works (detailed but accessible overview of the purpose of OP Mainnet and its key features).

OP Mainnet help center

OP Mainnet bridge

Optimism ecosystem

 

Relevant support articles

User Guide: Custom networks and sidechains 

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