Django vs FastAPI vs Flask

Side by side

Criterion	Django	FastAPI	Flask
Included features	ORM, admin, auth, forms, migrations	Validation, OpenAPI, DI	Routing and templates
Async support	Async views and partial async ORM	Async-first	Basic (async views run in threads)
Data layer	Django ORM	Bring your own (SQLAlchemy, SQLModel)	Bring your own (SQLAlchemy)
API documentation	Via DRF/drf-spectacular or Ninja	Automatic OpenAPI	Via extensions
Learning curve	Medium (lots to learn, well documented)	Low-medium (async and DI concepts)	Low
Structure for large teams	Strong conventions	You design it	You design it

When to choose each

Django

Batteries-included framework: ORM, migrations, admin, auth, forms, templates and security defaults; Django REST framework or Django Ninja for APIs.

Choose when

Database-backed products with users, admin screens and forms
Teams that value conventions and a stable, long-lived stack
Server-rendered sites plus APIs

Avoid when

Tiny services or pure async I/O gateways
When you can't use a relational database

FastAPI

Async API framework built on type hints: Pydantic validation, automatic OpenAPI docs, dependency injection and high throughput.

Choose when

JSON APIs and microservices
Async I/O-heavy services (calling other APIs, streaming, LLM apps)
Typed request/response models and generated clients

Avoid when

You need an admin, auth and ORM out of the box
Teams unfamiliar with async pitfalls (blocking calls in async code)

Flask

Minimal WSGI microframework: routing and request handling, with extensions for everything else.

Choose when

Small apps, internal tools and prototypes
You want to choose every component yourself
Maintaining or extending existing Flask apps

Avoid when

Large products where you'd rebuild Django's features from extensions
High-concurrency async workloads

Verdict

Pick Django for full products with a relational database, users and back-office needs; its admin, ORM and security defaults save months. Pick FastAPI for API-first services, especially async I/O-heavy ones, where typed models and automatic OpenAPI shine. Pick Flask for small apps and tools, or when you deliberately want to assemble your own stack. Many teams combine them: Django for the core product and FastAPI for specialised services.

Django vs FastAPI vs Flask

Side by side

When to choose each

Django

FastAPI

Flask

Verdict

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