FastAPI vs Flask

FastAPI vs Flask
Fact	FastAPI	Flask
Language	Python	Python
Licence	MIT	BSD-3-Clause
Stars	103k	75k
Latest	0.142.2	3.1.3
Last push	2026-10-06	2026-09-08
Release cadence	about 1 day between releases	about 182 days between releases
Active contributors	8 commit authors on the default branch in the last 90 days	3 commit authors on the default branch in the last 90 days
Flags	none	none

How they relate

FastAPI replaces Flask. Alternatives to Flask →
Full replacementAsync, with type hints driving validation and OpenAPI docs.

0.142.22026-09-30🐛 Allow startup when automatic OpenTelemetry configuration fails. PR #16418 by @tiangolo.
0.142.12026-09-29🐛 Fix repeated endpoint wrapping in included routers. PR #16414 by @tiangolo.
0.142.02026-09-29✨ Add native OpenTelemetry support. PR #16403 by @tiangolo.
0.141.12026-07-29🐛 Fix support for background tasks and headers from dependencies in app.frontend(). PR #16105 by @tiangolo.
0.141.02026-07-29✨ Add app.frontend(check_dir="auto"), to make local development more convenient with fastapi dev. PR #16102 by @tiangol…

3.1.32026-02-19This is the Flask 3.1.3 security fix release, which fixes a security issue but does not otherwise change behavior and s…
3.1.22025-08-19This is the Flask 3.1.2 fix release, which fixes bugs but does not otherwise change behavior and should not result in b…
3.1.12025-05-13This is the Flask 3.1.1 fix release, which fixes bugs but does not otherwise change behavior and should not result in b…
3.1.02024-11-13This is the Flask 3.1.0 feature release. A feature release may include new features, remove previously deprecated code,…
3.0.32024-04-07This is a fix release for the 3.0.x feature branch.

✓ signed The latest release, 0.142.2, carries a signature GitHub verified.

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✓ signed The latest release, 3.1.3, carries a signature GitHub verified.

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