Repo2txt is a web-based utility that transforms entire repositories into single formatted text files optimized for use in LLM prompts. It supports multiple sources including GitHub, local files, and zip uploads, with intelligent filtering via extension selection and gitignore pattern matching. The tool runs entirely in the browser with no server uploads, includes real-time token counting for GPT models, and handles large repositories with 10,000+ files through virtual scrolling and web workers.