FastAPI "python-multipart must be installed to use Form"/"UploadFile" in CI

FastAPI parses form fields and file uploads with the optional python-multipart package. Any endpoint using Form(...) or UploadFile raises at startup or request time if that package is not installed in CI.

What this error means

App startup or a form test fails with "RuntimeError: Form data requires \"python-multipart\" to be installed." or the equivalent message for UploadFile.

python

RuntimeError: Form data requires "python-multipart" to be installed.
You can install "python-multipart" with:

pip install python-multipart

Common causes

python-multipart is not a declared dependency

FastAPI lists it as optional; endpoints that use Form or UploadFile fail without it, and a clean CI environment does not have it.

Tests exercise a form or upload route

A test posts multipart data to a route that needs the parser, so the missing package surfaces only in CI.

How to fix it

Install python-multipart

Add the package to your dependencies so form and file endpoints work on every runner.

Terminal

python -m pip install python-multipart

Pin it in your dependency file

Declare it alongside FastAPI so CI never relies on it being incidentally present.

requirements.txt

# requirements.txt
fastapi
uvicorn[standard]
python-multipart

How to prevent it

Declare python-multipart whenever you use Form or UploadFile.
Install the fastapi[all] extra if you want the optional deps bundled.
Add a form or upload test so a missing parser fails CI early.