How to deploy a Flask app for free

You built a Flask app that works on localhost:5000. This guide gets it onto the internet with a real HTTPS link you can share, in about ten minutes, without paying anything.

What you need

• A Flask app that runs on your computer
• A free GitHub account
• A free Shipzo account (no credit card)

Step 1: Make your app ready for a server

On your laptop, Flask's development server listens on 127.0.0.1:5000. A hosting server tells your app which port to use through an environment variable called PORT, and it must listen on all network interfaces (0.0.0.0), not just localhost. Change the bottom of your main file like this:

app.py

import os
from flask import Flask, render_template

app = Flask(__name__)

@app.route("/")
def home():
    return render_template("index.html")

@app.route("/health")
def health():
    return {"status": "ok"}

if __name__ == "__main__":
    port = int(os.environ.get("PORT", 5000))
    app.run(host="0.0.0.0", port=port)

Keep the Flask object named app and the file named app.py (or main.py). Most hosts, Shipzo included, look for exactly that.

Write requirements.txt

The server installs only what is listed here. If you installed something with pip install and forgot to list it, the deploy fails with ModuleNotFoundError.

requirements.txt

Flask>=3.0,<4
gunicorn>=22

To capture everything your project uses, run pip freeze > requirements.txt inside your virtual environment, then delete lines you don't need.

Add a .gitignore

.gitignore

venv/
.venv/
__pycache__/
*.pyc
.env

Never commit .env files, passwords or API keys. You'll add secrets as environment variables on the server instead.

Step 2: Push your code to GitHub

Create an empty repository on GitHub, then run these commands in your project folder:

git init
git add .
git commit -m "First version"
git branch -M main
git remote add origin https://github.com/YOUR-USERNAME/YOUR-REPO.git
git push -u origin main

Step 3: Deploy it

1. Create a free Shipzo account and open New deployment.
2. Paste your repository link, for example https://github.com/you/flask-app.
3. Pick the Starter plan (enough for most Flask apps) and press Deploy.

Here's what happens automatically, in order:

Step 4: Updating your app

Just push again. Shipzo checks your branch every minute and redeploys new commits with zero downtime. If the new version fails its tests or health check, the old one keeps running.

git add .
git commit -m "Add contact page"
git push

Databases and secrets

Don't rely on a SQLite file for real data: every deploy starts from a clean container, so the file resets. Use a free hosted database such as Neon or Supabase (PostgreSQL) or MongoDB Atlas, and pass the connection string as an environment variable:

import os
DATABASE_URL = os.environ["DATABASE_URL"]

In Shipzo, open your project → Settings → Environment variables and add DATABASE_URL=.... Values are injected at runtime and masked in every log.

Common errors and fixes

Frequently asked questions