Deploy FastAPI to Vercel — uv, Vercel CLI, production

How to deploy FastAPI on Vercel with the sample repo below — useful if you’re new to Vercel or need a small public API. Steps after the demo section follow what worked in this repo; constraints are cross-checked against Vercel’s FastAPI / Python docs as of 2026-07-19.

What you’ll learn

End-to-end FastAPI on Vercel (official entrypoints + this sample’s layout)
uv for a local virtual environment
Vercel CLI: vercel dev, vercel, vercel --prod
Running pytest
Where requirements.txt / app need to live per current docs

Demo / template

Live sample:

FastAPI on vercel

fast-api-vercel-murex.vercel.app

You can also deploy from Vercel’s import of this repo:

You’ll need Git connected to Vercel.

Official zero-config starters also exist via vercel init fastapi and Vercel’s FastAPI templates (KB guide).

Environment (author machine)

macOS Sequoia 15.5
VS Code
zsh 5.9 (arm64-apple-darwin24.0)

Prerequisites

Python 3.12+ for local work. Vercel’s Python runtime (accessed 2026-07-19) supports 3.12 (default), 3.13, and 3.14 — pin with .python-version, pyproject.toml, or Pipfile.lock (Python runtime docs)
uv (install)
Vercel CLI (install) — FastAPI docs note a minimum CLI version of 48.1.8 for vercel dev / deploy flows

Official layout vs this sample

Per Deploy a FastAPI app on Vercel and the Python runtime docs (2026-07-19):

Export a FastAPI instance named app
Put it in a supported entrypoint: app.py / index.py / server.py / main.py / wsgi.py / asgi.py at the project root, or the same filenames under src/, app/, or api/
Or set tool.vercel.entrypoint in pyproject.toml for a custom module path
Dependencies: requirements.txt, pyproject.toml, or Pipfile (+ lock) at the project

This sample repo keeps code under api/app/main.py (exports app) and routes everything there via vercel.json:

{
  "routes": [{ "src": "/(.*)", "dest": "api/app/main.py" }],
  "functions": { "api/app/main.py": { "maxDuration": 60 } }
}

That nested path is this repo’s choice, not a Vercel rule that every FastAPI app must live under api/. Root-level main.py / app/main.py / api/index.py are all valid on current docs.

Author note: When I first shipped this sample, putting the app only at the repo root without a matching entrypoint/route failed for me. Prefer a documented entrypoint (or an explicit vercel.json / tool.vercel.entrypoint) rather than assuming api/ is mandatory.

requirements.txt at the repo root is what this sample uses and what Vercel installs from. Official docs also accept pyproject.toml / Pipfile — root requirements.txt is sufficient, not the only option.

On deploy, FastAPI becomes a single Vercel Function (Fluid compute by default). Bundle size and other Functions limits apply.

Local setup

1. Clone

git clone https://github.com/testkun08080/FastAPI-vercel.git
cd FastAPI-vercel

2. Virtual environment

uv venv -p 3.12
uv pip install -r requirements.txt

3. Run the app

uv run -m api.app.main

Open the local URL in a browser to verify.

For behavior closer to production, prefer vercel dev (see below) so the same app instance and routing are exercised.

Tests

1. Test dependencies

uv pip install -r requirements_test.txt

2. Pytest

uv run pytest --html=report.html --self-contained-html --log-level=INFO

Vercel CLI: dev → preview → production

Local dev (Vercel-like)

vercel dev

Preview deploy

vercel

Production deploy

vercel --prod

Official docs

Summary

FastAPI deploys on Vercel via the Python runtime when you export app at a supported entrypoint (or configure one explicitly).
This sample uses api/app/main.py + vercel.json, uv locally, and requirements.txt at the repo root — that combo worked for me; it is not the only valid layout.
CLI path vercel dev → vercel → vercel --prod still matches current docs for preview and production.

See also: Currency Converter Board — embeddable multi-currency rates (same author).