Test on Sepolia before deploying to mainnet
Every project has a Network toggle (Testnet / Mainnet) inside the chain picker. Testnet = free practice deploy with real block-explorer + marketplace presence but zero monetary value. Mainnet = the real release. Recommended path is always testnet first.
Where the toggle lives
Open /create/generative → 'Destination blockchain'. Under the Ethereum card you'll find a Network sub-toggle: 'Sepolia testnet' or 'Ethereum mainnet'. New projects default to Testnet for safety, and the deploy step re-checks that your wallet is on the matching network before it signs anything.
What testnet actually means
Sepolia is a full clone of Ethereum. Block explorers (sepolia.etherscan.io), wallets (MetaMask, Rainbow) and marketplaces (testnets.opensea.io) all work - the only difference is that the ETH has no value. You can rehearse the entire deploy + Collect flow end-to-end without spending real money.
Get free testnet funds
sepoliafaucet.com (Alchemy, 0.5 ETH / 24h with a free account) or cloud.google.com/application/web3/faucet/ethereum/sepolia (Google, no sign-up, lower amounts but reliable). Faucet ETH lands in seconds; ignore the 'value' column on Etherscan since it'll show $0.
What happens at deploy time
When you click Deploy, artsunami reads your project's Network setting and checks your connected wallet's chain id. If they don't match, the green Deploy button is replaced by an orange 'Switch wallet to {Mainnet|Sepolia}' button - clicking it asks your wallet to swap. The deploy button unlocks automatically once the wallet aligns. You can't accidentally deploy to mainnet when the project is set to testnet.
The recommended path
1) Set Network to Testnet and deploy on Sepolia. 2) Open your Collect page at /c/<slug>?preview=1 and try a self-Collect with a second test wallet. 3) Check the render at testnets.opensea.io/assets/sepolia/<contract>/0 - token ids start at 0 - to confirm the on-chain script resolves. 4) Flip Network to Mainnet and hit Deploy again: same project, same script, on the real network. Total cost of the dry run is just the Sepolia gas (free).
Other chains (roadmap)
Only Ethereum is selectable today - mainnet for production, Sepolia for free rehearsals. The EVM L2s (Base, Optimism, Arbitrum, Polygon) and Tezos are wired in the codebase but turned off; Solana and Bitcoin Ordinals are roadmap items. Nothing else appears in the picker. Coins are the exception: they launch and trade on Base, and on Base Sepolia when the app runs in coin test mode (see /help/coins).
Nami lives at the top of the Help center. It knows every topic in this center and can walk you through your specific collection, wallet or transaction.