A rate limiting library for Starlette and FastAPI adapted from flask-limiter.

Note: this is alpha quality code still, the API may change, and things may fall apart while you try it.

The documentation is on read the docs.

Quick start


slowapi is available from pypi so you can install it as usual:

$ pip install slowapi


Most feature are coming from (will come from) FlaskLimiter and the underlying limits.

Supported now:

  • Single and multiple limit decorator on endpoint functions to apply limits
  • redis, memcached and memory backends to track your limits (memory as a fallback)
  • support for sync and async HTTP endpoints
  • Support for shared limits across a set of routes

Limitations and known issues

  • The request argument must be explicitly passed to your endpoint, or slowapi won’t be able to hook into it. In other words, write:
    async def myendpoint(request: Request)

and not:

    async def myendpoint()
  • websocket endpoints are not supported yet.

Developing and contributing

PRs are more than welcome! Please include tests for your changes ?

The package uses poetry to manage dependencies. To setup your dev env:

$ poetry install

To run the tests:

$ pytest


Credits go to flask-limiter of which SlowApi is a (still partial) adaptation to Starlette and FastAPI. It’s also important to mention that the actual rate limiting work is done by limits, slowapi is just a wrapper around it.