# Zero\-configuration Flask backends

**Published:** October 10, 2025 | **Authors:** Ricardo Gonzalez, Marcos Grappeggia

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[Flask](https://flask.palletsprojects.com/), one of the most popular [Python](https://vercel.com/docs/functions/runtimes/python) web application frameworks, can now be deployed instantly on Vercel with no configuration changes needed.

**app.py**
```python
from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello_world(): 
    return "<p>Hello, World!</p>"
```

Vercel's [framework-defined infrastructure](https://vercel.com/blog/framework-defined-infrastructure) now recognizes and deeply understands Flask applications. This update removes the need for redirects in `vercel.json` or using the `/api` folder.

Backends on Vercel use [Fluid compute](https://vercel.com/fluid) with [Active CPU pricing](https://vercel.com/blog/introducing-active-cpu-pricing-for-fluid-compute) by default. This means your Flask app will automatically scale up and down based on traffic, and you only pay for time where your code is actively using CPU.

[Deploy Flask on Vercel](https://vercel.com/templates/python/flask-python-boilerplate) or visit the [Flask on Vercel documentation](https://vercel.com/docs/frameworks/backend/flask).

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📚 **More updates:** [View all changelog entries](/changelog/sitemap.md) | [Blog](/blog/sitemap.md)