> ## Documentation Index
> Fetch the complete documentation index at: https://docs.optimism.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Build interoperable apps on OP Stack devnet

> Learn about deploying contracts, cross-chain messaging, and tutorials to help you build applications on OP Stack chains.

Reimagine your app with OP Stack interop to deliver the unified UX your users expect. Hack on net-new, bold use cases on Interop devnet.

<Info>
  Explore the [Superchain Dev Console](https://console.optimism.io/?utm_source=op-docs\&utm_medium=docs) to build, launch, and grow your app on OP Stack chains.
</Info>

## Connect to OP Stack Interop

Choose your development environment to build, test, and quickly iterate on your apps.

| Environment           | Purpose                                   | Getting Started                                                        |
| --------------------- | ----------------------------------------- | ---------------------------------------------------------------------- |
| **Local development** | Rapid iteration and testing with Supersim | [Setup Supersim guide](/app-developers/tutorials/development/supersim) |
| **Interop devnet**    | Large-scale testing on testnets           | [Network specs](/app-developers/guides/building-apps)                  |

## Tools & resources for building interoperable apps

| Tool                                                                                        | Description                                                                |
| ------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------- |
| [Superchain Faucet](https://console.optimism.io/faucet?utm_source=op-docs\&utm_medium=docs) | One-stop shop to grab testnet ETH for any OP Stack network.                |
| [Supersim](/app-developers/tools/supersim)                                                  | Local multi-chain testing environment for smart contracts.                 |
| [Super CLI](https://github.com/ethereum-optimism/super-cli)                                 | Command-line tool for seamless multichain app deployment and testing.      |
| [Superchain Relayer](https://github.com/ethereum-optimism/superchain-relayer)               | UI for monitoring and managing cross-chain transactions.                   |
| [Interop Docs](/op-stack/interop/explainer)                                                 | Comprehensive Interop information in the Optimism Docs.                    |
| [Developer Console](https://console.optimism.io/?utm_source=op-docs\&utm_medium=docs)       | Comprehensive tool to build, launch, and grow your app on OP Stack chains. |
| [Developer Support GitHub](https://github.com/ethereum-optimism/developers/discussions)     | Quick and easy developer support.                                          |

## Handy step-by-step guides

<CardGroup cols={2}>
  <Card title="Supersim tutorials" icon="flask" href="/app-developers/tutorials/supersim" />

  <Card title="Interop tutorials" icon="network-wired" href="/app-developers/tutorials/interop" />

  <Card title="Transaction tutorials" icon="arrow-right-arrow-left" href="/app-developers/tutorials/transactions" />

  <Card title="Bridging tutorials" icon="bridge-water" href="/app-developers/tutorials/bridging" />
</CardGroup>

## Discover and build net-new use cases with OP Stack Interop

There is so much more than just bridge abstraction. Hack on the various cutting-edge applications that are uniquely enabled by OP Stack Interop. Here are some ideas to get you started:

| Superloans                                                                         | Superlend                                                                                                           | SuperCDP                                                                                                          |
| :--------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------ | :---------------------------------------------------------------------------------------------------------------- |
| Use collateral on ChainA and ChainB to execute an arbitrage opportunity on ChainA. | Deposit ETH into lending protocols across chains for optimal yield, with automatic rebalancing based on best rates. | Collateralized crosschain debt protocol that holds assets and issues cross-chain tokens on user preferred chains. |