What is the difference between Flask-RESTful and Flask-RESTX?

Flask-RESTful is an extension for building REST APIs with Flask, providing resource-based routing (class-based views where methods map to HTTP verbs), request parsing with reqparse, and response marshaling. Flask-RESTX is a fork and successor of Flask-RESTPlus, which extends Flask-RESTful with automatic Swagger documentation generation, namespaces (similar to Blueprints), and declarative API models. Flask-RESTX is the more feature-complete choice for documented REST APIs. However, both are less commonly used now compared to FastAPI, which provides all these features (auto-docs, validation, serialization) out of the box with better performance and type safety. Flask-RESTX is still a good choice if you have an existing Flask codebase and need to add Swagger documentation without a full migration to FastAPI.