Open a template or write your own. Run compiles the active file in your browser; the panel beside it deploys through your wallet and lets you call what you deployed.
What runs where
The compiler is solc in a Web Worker on your machine. The wallet is yours, discovered through EIP-6963. Reads go to the chain's public RPC or your wallet's. The only thing that can reach our server is a workspace you choose to save.
Saving
Signed out, your workspace lives in this browser and survives a reload. A membership keeps five or fifty workspaces in your account and opens them anywhere.