Replica

Prototyping has a strange place in software teams: everyone agrees you should test ideas before building them, and everyone also agrees that setting up a realistic prototype takes long enough that the idea usually just gets built instead. Replica is GitHub's open-source, MIT-licensed swing at that gap. It uses AI to turn a described change into an interactive prototype that runs inside your own design system, working from components, patterns, and documentation that your designers create and approve, so the result is supposed to resemble your actual product rather than a demo that gets thrown away the moment a developer sees it.

Replica is not one app but four pieces that work together. The Starter creates a local prototype project with agent skills and a working app you can adapt. The Copilot canvas extension opens your local prototype right next to your Copilot conversation, so you describe a change and watch it happen side by side. Replica Hub, which is optional, hosts published prototypes so teammates can try them and leave comments, and a GitHub build action packages prototypes for publishing. Local prototyping needs no server and no Hub, and GitHub does not host Hub for you: your organization deploys it on its own infrastructure, with documentation unusually upfront about data handling, down to a stated 90-day retention for Hub activity events.

One thing keeps this listing honest: MIT-licensed code does not automatically mean free usage. Viewing a finished prototype or reviewing one in Hub costs nothing, but creating prototypes runs through the GitHub Copilot app with a GitHub sign-in, and the AI access behind it requires either a Copilot plan (a free tier with monthly limits exists) or your own model provider key, with the provider's costs and terms applying. Free code, bring your own AI. Replica is brand new and under active development, so expect rough edges. Read our full discovery: Replica: GitHub's Open-Source Tool Turns Ideas Into Interactive Prototypes.