Guide to Using Arbitrum Rinkeby Testnet on Metamask

Posted on:29 March 2022 at 10:00

Ethereum is a protocol with multiple networks which can be used for various purposes, such as development and testing. Mainnet Ethereum is where value transfers and storage of critical information happens, along with a rising number of Layer 2s, such as Arbitrum and Optimism.

Sometimes, however, you want to try out new features or protocols before committing your precious ETH to irreversible actions. That’s when public testnets step in. Like other Ethereum networks, testnets do not carry over your funds from the mainnet but act as independent networks. That’s why bridges have been blowing up lately; they allow moving tokens from one network to another (e.g. from Mainnet to Arbitrum).

As testnet tokens have no real-world value attached to them, you don’t (and shouldn’t) use bridges to move funds from mainnet to testnet. Instead, you use faucets to get testnet tokens for free. There are plenty of testnets out there, both private and public. Public testnets are great for trying out deployments before pushing them to the mainnet or interacting with a greater number of testers with less overhead. Private networks allow you more control over your processes & IP. Some of the better known Ethereum public testnets include Rinkeby, Görli, Ropsten, and Kovan. These testnets come preinstalled in popular browser wallets, such as Metamask.

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What’s Arbitrum Rinkeby?

Arbitrum is an optimistic rollup, a Layer 2, on Ethereum. It functions like Ethereum but independently of the mainnet. It’s called an optimistic rollup as it only requires a bare amount of information to be submitted with transactions, only requiring proof if fraud is suspected. That’s why there’s a delay between getting assets from Arbitrum to Mainnet — it ensures enough time has passed for the network to detect fraud. Abitrum is an optimistic rollup because the transactions are bundled (rolled up) and committed to the Mainnet in one patch. This socialises costs across Arbitrum users, making its use much cheaper than Mainnet.

Arbitrum Rinkeby is an Arbitrum testnet. This means there’s no value associated with the transactions happening on Arbitrum Rinkeby. It’s a great testing environment for protocols working on Arbitrum.

How to Set Up Arbitrum Rinkeby in Metamask?

As Arbitrum Rinkeby is “just” another Ethereum network, its setup is as easy as adding any other network:

  1. Click the network selector button next to the Metamask icon (it probably says “Ethereum Mainnet” by default).
  2. Click the “Add Network” -button.
  3. This takes you to a page that allows you to add information about a new network. If this were a non-testnet environment, I’d tell you to be extremely careful about the information you input here. But as it’s a testnet, you can copy and paste the suggested inputs from here or head over to Offchain Labs’ dev centre for up to date info.
  4. Done! You can now use the network selector button to change from Ethereum Mainnet to Arbitrum Testnet.

If you are using different addresses for testing and real-world use (which I highly recommend for privacy purposes, if nothing else), be sure always to double-check your addresses!

Getting Testnet ETH

After you’ve added the new network, you’ll notice (most likely) that your balance is a sad 0 ETH. To fix this, you’ll need some ETH. Luckily, we are on testnet, and ETH comes for free! 😎 You can get Arbitrum Rinkeby ETH from various faucets.

I’ll take you through claiming from rinkebyfaucet.com:

  1. Head over to https://rinkebyfaucet.com/

  2. Simply enter your testnet address to the wallet address box and hit “Send Me ETH”. You will notice that the transaction went through, but nothing shows up in your wallet. That’s because the faucet provided you with mainnet Rinkeby ETH! So you’ll need to bridge testnet ETH from mainnet Rinkeby to Arbitrum Mainnet:

  3. Switch your Metamask network from “Arbitrum Testnet” to “Rinkeby Test Network”. (If you don’t see this option in the Metamask networks list, click the “Show/hide test networks” button at the top and toggle the “Show test networks” on in the settings.)

  4. You can now see some ETH in your mainnet Rinkeby test wallet.

  5. Head over to a bridge, such as the Tracer Perpetual Pools Bridge

  6. Ensure you have selected “Rinkeby” in the “From” -field and “Arbitrum Rinkeby” in the “To” -field. You wouldn’t want to bridge on the mainnet accidentally!

  7. Select “ETH” as the asset.

  8. Choose a slightly lower amount than your account balance to leave some ETH for gas.

  9. Hit “Bridge to Arbitrum Rinkeby”.

  10. Approve the transaction as usual.

  11. Get ready to wait a few minutes. Bridging is not instant.

  12. Switch your Metamask back to “Arbitrum Testnet” and wait a bit more if necessary. Now, you should be able to see your Arbitrum Rinkeby balance update.

You can track your transaction history on the Arbitrum Testnet in precisely the same way as on the Arbitrum mainnet. All your transactions show up in Metamask and block explorers like the Arbiscan Testnet explorer.

You can also transact and interface with supported applications as usual. And pay gas as usual.

If you liked this article, give it a clap and follow me on Twitter. If you’d like to trial Tracer’s Perpetual Pools v2 before its mainnet release, follow me on Medium for updates and instructions on the upcoming incentivised launch in early April 2022.