Overview
Flask is a BSD-licensed micro web framework for Python, architected by the Pallets Project to provide a minimalist foundation for web application development. Unlike 'batteries-included' frameworks like Django, Flask prioritizes extensibility, allowing developers to choose their preferred database abstraction layers, form validation tools, and authentication mechanisms. In the 2026 landscape, Flask remains the industry standard for deploying lightweight AI/ML inference endpoints, serving as the primary 'thin wrapper' for LLM-based agents and RAG (Retrieval-Augmented Generation) architectures. Its core architecture is built upon the Werkzeug WSGI toolkit and the Jinja2 template engine. Technically, Flask leverages a thread-local context system to handle requests and provides a robust Blueprint system for modular application design. Its simplicity facilitates rapid prototyping while its performance characteristics enable high-concurrency microservices when deployed behind production-grade WSGI servers like Gunicorn or Nginx Unit. As of 2026, its ecosystem continues to thrive, particularly in the MLOps space where Flask is used to bridge complex Python logic with front-end React or Next.js interfaces via RESTful APIs.