Langfa.st is a fast, browser-based AI prompt testing playground designed for developers and product teams. It lets you experiment with prompts using live LLM outputs, dynamic variables (like Jinja2), and structured response formats.
Unlike traditional testing tools, Langfa.st doesn’t require signup or configuration. You just open the app and start iterating. Share results with your team, compare outputs side-by-side, and refine your prompts faster — all in one simple, transparent interface.
