How to Build and Deploy on Starknet: A Developer Guide

Starknet is an Ethereum Layer 2 network. It executes transactions away from Ethereum’s main chain, groups them and uses STARK validity proofs to show that the resulting state is valid. Ethereum provides settlement and security for those proofs, while Starknet handles the app’s transaction execution.

For developers, the key difference is that Starknet uses Cairo for smart contracts rather than Solidity as its native contract language. Its account model also supports smart accounts, where wallet behavior can be implemented in contract code. That can enable features such as custom transaction validation, but it means account behavior and wallet compatibility need to be part of your design and testing.

Starknet may suit you if you want an Ethereum-connected application and are prepared to work with Cairo and its tooling. It is not simply an EVM chain with different fees: contracts, accounts and integrations may need Starknet-specific implementations. Before committing, check that the wallets, indexers, data services and other infrastructure your app needs support your intended Starknet workflow.

Start by deciding what your app needs from a chain, then compare Starknet against those requirements. Don’t choose it only because you expect transactions to be cheaper than on Ethereum: fees vary, and your application’s design, user experience and tooling needs matter too.

Use this checklist before starting a production build:

• Language: Are you willing to write and maintain Cairo contracts rather than relying on an existing Solidity codebase?
• Users: Can your intended audience access Starknet through wallets and interfaces that support the features you need?
• Integrations: Do your required oracles, indexers, bridges and third-party services work with Starknet?
• Operations: Can your team monitor transactions, handle RPC failures and support users who make mistakes?
• Security: Can you budget time and resources for testing, code review and, where appropriate, an independent audit?

If your project depends heavily on a Solidity-only library or a specific Ethereum integration, investigate the migration effort before building. A small proof of concept can expose gaps early: build one core contract, connect a wallet and test the main user action before expanding the system.

A typical Cairo workflow includes Scarb for project management and builds, Starknet Foundry for testing and development, and a Starknet-compatible wallet and RPC endpoint for interacting with a network. For a web app, a Starknet client library can help your frontend communicate with contracts and wallets. Check current Starknet documentation for installation steps and supported versions, since tool interfaces can change.

A sensible first setup is:

1. Install the supported Cairo toolchain and Scarb using the current official instructions.
2. Create a small sample project and build it locally.
3. Add Starknet Foundry and run the sample tests.
4. Configure a local development environment or testnet connection.
5. Connect a compatible wallet only after you understand which network it is set to.

Keep compiler and dependency versions consistent across your team and build system. Commit lockfiles where the toolchain supports them, and document the commands needed to reproduce a build. For RPC access, check rate limits, uptime terms, data coverage and pricing before relying on a provider in production. Avoid putting provider secrets or wallet credentials in frontend code or public repositories.

Write down the contract’s responsibilities before you start coding: what state it stores, who can change that state, what conditions must hold for each action and what events an app or indexer needs to observe. Keep permission checks close to the state changes they protect, and make invalid state transitions fail safely.

Cairo contracts are compiled through Starknet’s contract toolchain. You may encounter Sierra, an intermediate representation, and CASM, the form used for execution. You do not need to implement these layers yourself, but you should use compatible tooling and understand the artifacts your build produces. Treat compiler output as something to verify in your release process, not as a substitute for reviewing the source.

For a first contract, keep the scope narrow: implement one core action, define its access rules, and write tests for both allowed and rejected calls. Avoid copying a contract from another chain and assuming it behaves the same on Starknet. Differences in language, account behavior, transaction handling and integrations can change the security assumptions. If you are adapting an existing system, make a migration plan that identifies every dependency and feature that needs a Starknet-specific replacement.

Test locally before using a public network. Unit tests should cover normal outcomes, boundary values, invalid inputs and access-control failures. Add tests for state changes across multiple calls, since a contract that works in isolation may fail when other contracts or account logic are involved.

Then test the full user journey on a public Starknet test network:

1. Deploy the test version of your contract.
2. Connect the wallet and check the selected network.
3. Run the main user action and confirm the expected state change.
4. Test rejected transactions, wallet cancellation and RPC interruptions.
5. Confirm your app displays transaction status clearly, including delays or failures.

Testnet tokens are for testing and should not be treated as having real value. A testnet also cannot guarantee that mainnet will behave identically: network conditions, fee estimates, integrations and contract interactions can differ. Use automated tests in your build pipeline, review important changes before merging, and keep a record of the deployed test contract and build version. For applications that handle valuable assets, consider independent security review before mainnet deployment.

Treat mainnet deployment as a release, not a single command. First verify the network, account and compiled contract artifact. Confirm the deployment account has the assets needed for fees, and simulate or review the deployment steps using the current tools. A mistaken network selection or an incorrect constructor argument can create expensive problems that are difficult or impossible to reverse.

Before release, check each item:

• The deployed source and artifact match the version reviewed by your team.
• Contract permissions, ownership and upgrade controls are intentional.
• The frontend points to the correct network and contract address.
• Critical app flows have been tested with the intended wallet types.
• You have a plan for monitoring errors and communicating incidents.

Starknet transaction costs are not a fixed development price. They can include Starknet execution and costs associated with publishing transaction data or proofs to Ethereum; the amount depends on the transaction and changing network conditions. You may also pay for RPC access, infrastructure, audits and ongoing engineering. Estimate costs using current network tools and test representative transactions. Do not promise users a fixed fee unless your app can support that commitment under changing conditions.

A Starknet app inherits risks from its contracts, accounts, integrations and the Ethereum settlement layer. A validity proof can demonstrate that transactions follow the network’s rules; it does not prove that your application’s rules are correct or that its interface is safe. Audit the code and assumptions that matter to your users.

Pay particular attention to privileged roles, upgrade mechanisms, external contract calls, oracle data, signature handling and recovery processes. If your app uses a bridge, users also take on bridge-specific risks and delays; make the supported routes and asset behavior clear. Do not assume a token or contract on Starknet is trustworthy just because it is available in a wallet.

Protect users and operators by keeping deployment keys secure, limiting administrative access and documenting emergency procedures. Never put private keys or seed phrases in source code, build logs or browser storage. Use separate accounts and credentials for development and production. For a high-value application, arrange independent review and have a plan for pausing or limiting harmful activity if the contract design allows it. Be clear about what can and cannot be reversed after deployment.

New Starknet projects often run into a few avoidable problems. Check these before you expand beyond a prototype:

• Assuming EVM compatibility: Starknet uses Cairo and has its own account and contract conventions. Verify each library and integration rather than assuming Solidity code will work unchanged.
• Testing only successful calls: Include rejected inputs, permission failures, wallet errors and interrupted RPC requests in your test plan.
• Ignoring fee variability: Measure representative transactions and explain that fees can change. Avoid relying on a single estimate for every user action.
• Deploying without verifying the network: Confirm the wallet, RPC endpoint and deployment account are all configured for the intended network.
• Treating a testnet as a security audit: Testnets help validate workflows, but they do not establish that a contract is safe.
• Leaving key management until release: Decide early who can deploy, upgrade or administer contracts, and protect those accounts accordingly.

Keep the first release small, make contract and frontend versions traceable, and monitor behavior after launch. If an integration or network component changes, retest the affected flows before depending on it in production.