Langfa.st

LangFast is an online LLM playground designed for rapid testing, debugging, and evaluation of prompts across multiple large language models using your own API keys. It allows users to compare model outputs side-by-side, stream responses in real time, create and share test cases with links, and use advanced features like variables and templates. This platform is ideal for developers, prompt engineers, and AI researchers seeking an efficient environment for iterative prompt development and model comparison.