microsoft/poml

Employs an HTML-like syntax with semantic components (``, ``, ``) combined with a CSS-like styling system to decouple prompt content from presentation formatting, enabling format-agnostic LLM interactions. Includes a built-in templating engine supporting variables, loops, and conditionals for data-driven prompt generation, plus specialized data components for embedding external sources (documents, tables, images). Available via SDKs for Node.js and Python, with VS Code extension providing syntax highlighting, real-time previews, and integrated testing capabilities.

4,865 stars.