What React or Next.js project could I build for interviews besides a todo app?

Pick a small problem someone actually has, then make a tool around it. A food and macro tracker is one example: enter meals, see totals against a target, and save everything in local storage.

That gives you room to work on forms, validation, useful feedback, and a clear interface without needing a server. If you can get someone to try it, their feedback can help you decide what to polish.

Build a visual JSON or Markdown editor. The interesting part isn't just displaying text. Try an interactive editing interface with undo and redo, and think through how the history should behave when users make several changes in a row.

Keep the first version small. A focused editor with reliable state handling gives you something concrete to discuss in an interview.

A local CSV or log analyzer could be a nice frontend challenge. Let users drop in a file, parse it in the browser, and show a dashboard that helps them find patterns. Start with modest files, then see how the interface behaves with larger ones.

If the idea needs accounts or shared data, you don't have to build every backend piece yourself. Supabase or Firebase can handle authentication and storage while you concentrate on the React interface. Pick a narrow use case so setup doesn't eat the whole project.