Langfa.st - Showcase Project
Listed July 6, 2025
About Langfa.st
Langfa.st is a fast, no-signup AI prompt testing playground for developers
Langfa.st is a flexible, no-signup playground for testing and optimizing AI prompts. It supports dynamic variables, Jinja2-style templates, and structured outputs, enabling fast and reliable testing without writing backend code. Teams can preview LLM responses in real-time, compare outputs side-by-side, and reuse prompts through shareable public links. No installation or setup required — just open the editor and start experimenting. Langfa.st is ideal for developers, PMs, and AI teams who want to iterate faster and reduce manual prompt testing. Built by a team experienced in scaling AI-powered SaaS products to over 15M users, it removes friction from prompt engineering workflows and gives you full control over performance, cost, and accuracy — all in one intuitive interface.
Project details
Built with: REACT
Website: https://langfa.st/