Why this app does not open like a normal static page
The Flask Authentication App is a backend project. It needs a Flask server running locally, because the browser alone cannot create users, hash passwords, store sessions in cookies, or read the SQLite database.
What Flask is
Flask is a lightweight Python web framework. It lets Python handle routes like /signup, /login, and /protected.
What a Flask server does
The server runs the Python code, talks to SQLite, checks JWT cookies, and returns HTML pages to the browser.
Why GitHub is not the demo
A GitHub repo only shows the code. It does not run the app, so people who are new to Flask may think the project is broken.
To actually use the app, the project must be started with python app.py inside the Flask folder after installing the Python packages.