APIFlask
A lightweight web API framework based on Flask.
Decision gist · record as of 2026-08-14
Yes. APIFlask is actively maintained, has no known vulnerabilities, installs with low friction, and solves a real problem—reducing boilerplate in Flask API development while keeping you in the Flask ecosystem. It's suitable for production use (Development Status: Production/Stable) and works with modern Python versions. Choose it if you want Flask's flexibility with structured API patterns and auto-generated docs, without adopting a heavier framework.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.9+ and Flask 2.1+.
- Low friction install with a pure-Python wheel.
- Depends on seven runtime packages including Flask, marshmallow, Pydantic, and webargs.
License · maintenance · safety
MIT (permissive) — MIT license is permissive and imposes no restrictions on commercial or private use, modification, or redistribution.
last release 2026-06-23 (52 days) · last repo commit 2026-08-10 · 1,131 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 211,229 downloads/mo, #9,482 on PyPI
Alternatives
Verify before relying
pip install apiflask
from apiflask import APIFlask, Schema
from apiflask.fields import String
app = APIFlask(__name__)
class PetOut(Schema):
name = String()
@app.get('/pets/<int:pet_id>')
@app.output(PetOut)
def get_pet(pet_id):
return {'name': 'Kitty'}- Performance characteristics under load compared to other Flask-based API frameworks.
- Maturity and stability of Pydantic model adapter relative to marshmallow schemas.
- Real-world async support reliability and any known gotchas with Flask 2.0+ async features.
What it is and what it does
APIFlask is a thin wrapper around Flask that adds structured API development patterns. It lets you declare request and response schemas using either marshmallow or Pydantic, then automatically validates incoming JSON, deserializes it into your schema, and serializes responses back out—all while generating an OpenAPI specification and interactive Swagger UI documentation on the fly. You write decorators like `@app.input()` and `@app.output()` on your route functions, and APIFlask handles the plumbing: validation errors return JSON, successful responses are formatted consistently, and your API docs stay in sync with your code.
It's built on top of Flask's ecosystem (using flask-marshmallow, webargs, apispec, and flask-httpauth) and remains fully compatible with Flask extensions and patterns. The framework is ORM/ODM-agnostic, so you can use it with SQLAlchemy, MongoDB, or any data layer. It supports both synchronous and asynchronous route handlers, and you can choose between multiple documentation UIs (Swagger UI, Redoc, Elements, RapiDoc, RapiPDF).
Use it for
- Build REST APIs with automatic request validation and OpenAPI docs without writing boilerplate schema code.
- Migrate from plain Flask to a structured API framework while keeping all existing Flask extensions and middleware.
- Generate interactive API documentation (Swagger UI) automatically from your route decorators and schemas.
- Validate incoming JSON against marshmallow or Pydantic schemas and return consistent error responses.
- Implement API authentication using Flask-HTTPAuth with minimal setup code.
- Serialize ORM/ODM model instances directly to JSON responses without manual conversion.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
APIFlask is actively maintained, has no known vulnerabilities, installs with low friction, and solves a real problem—reducing boilerplate in Flask API development while keeping you in the Flask ecosystem. It's suitable for production use (Development Status: Production/Stable) and works with modern Python versions. Choose it if you want Flask's flexibility with structured API patterns and auto-generated docs, without adopting a heavier framework.
Install
apiflask on PyPI
Before you install
Low friction install with a pure-Python wheel. Depends on seven runtime packages including Flask, marshmallow, Pydantic, and webargs. Actively maintained with a recent release and ongoing commits.
Requires Python 3.9+ and Flask 2.1+.
License in practice
MIT license is permissive and imposes no restrictions on commercial or private use, modification, or redistribution.
Quickstart
pip install apiflask
from apiflask import APIFlask, Schema
from apiflask.fields import String
app = APIFlask(__name__)
class PetOut(Schema):
name = String()
@app.get('/pets/<int:pet_id>')
@app.output(PetOut)
def get_pet(pet_id):
return {'name': 'Kitty'}Verify before relying
- Performance characteristics under load compared to other Flask-based API frameworks.
- Maturity and stability of Pydantic model adapter relative to marshmallow schemas.
- Real-world async support reliability and any known gotchas with Flask 2.0+ async features.
Package facts
| License | MIT permissive |
| Python support | Not specified |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 7 packagesflaskflask-marshmallowmarshmallowwebargsflask-httpauthapispecpydantic |
| Maintenance | Actively maintained 52 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 211,229 / month, #9,482 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableEnvironment :: Web EnvironmentFramework :: FlaskIntended Audience :: DevelopersLicense :: OSI Approved :: MIT LicenseOperating System :: OS IndependentProgramming Language :: Python :: 3 :: OnlyProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: 3.9Topic :: Internet :: WWW/HTTP :: Dynamic ContentTopic :: Internet :: WWW/HTTP :: WSGITopic :: Internet :: WWW/HTTP :: WSGI :: ApplicationTopic :: Software Development :: Libraries :: Application Frameworks |
Evidence: apiflask-3.1.1-py3-none-any.whl
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See also flask-openapi3 · Flask · flask-apispec · tapipy · Flask-API · Flask-Pydantic · flask-marshmallow · flask-pydantic-spec · apispec-webframeworks