Does Flask Work With Netlify?
Flask can run on Netlify via serverless functions, but requires adaptation from traditional WSGI deployment and has cold-start limitations.
Quick Facts
How Flask Works With Netlify
Flask is a traditional WSGI framework designed for long-running server processes, while Netlify Functions are event-driven, stateless serverless functions with strict execution timeouts (10 seconds for free tier, 26 seconds paid). To use Flask on Netlify, you must either wrap Flask in a serverless function handler using a compatibility layer like `serverless-wsgi` or `flask-lambda`, or refactor your app to use Netlify Functions directly. The WSGI wrapper approach allows existing Flask apps to deploy with minimal changes—you create a handler function that converts API Gateway events into WSGI requests. However, you'll lose persistent connections, background jobs, and certain middleware features. This approach works well for lightweight APIs and monolithic Flask apps under 50MB (function size limit), but isn't ideal for apps requiring real-time features or complex session management. For the best Netlify experience with Python backends, consider using Netlify Functions with a microservices architecture or exploring alternatives like Vercel or Railway that offer better Python support.
Best Use Cases
Flask on Netlify Functions with serverless-wsgi
pip install flask serverless-wsgi && npm init -y && npm install --save-dev netlify-cli# flask_app.py
from flask import Flask, jsonify
app = Flask(__name__)
@app.route('/api/hello', methods=['GET'])
def hello():
return jsonify({'message': 'Hello from Flask on Netlify!'})
@app.route('/api/items', methods=['POST'])
def create_item():
return jsonify({'id': 1, 'status': 'created'}), 201
if __name__ == '__main__':
app.run(debug=True)
# netlify/functions/api.py
from serverless_wsgi import handle
from flask_app import app
def handler(event, context):
return handle(app, event, context)Known Issues & Gotchas
Function cold starts add 1-3 second latency on first request after idle period
Fix: Use Netlify's scheduled functions to keep instances warm, or implement client-side retry logic with exponential backoff
Flask session middleware and server-side storage don't work across function invocations
Fix: Switch to stateless authentication (JWT tokens) or use external session stores like Redis/DynamoDB instead of Flask's default session
Request/response cycle is limited to function timeout (10-26 seconds)
Fix: Offload long operations to background jobs via webhooks, queues, or async services; keep Flask endpoints under 5 seconds
File uploads and large payloads hit 6MB payload size limit
Fix: Use presigned URLs to upload directly to Netlify Blobs or external storage (S3, Cloudinary) instead of routing through Flask
Alternatives
- •Next.js with Python serverless backend (Vercel) - better DX for full-stack JavaScript teams
- •FastAPI with Vercel/Railway - modern async Python framework with superior serverless support
- •Django on Heroku/Railway - more batteries-included, better for monolithic apps needing database ORM
Resources
Related Compatibility Guides
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