What is Flask's g object?

The g object in Flask is a global namespace object available during the lifetime of a request for storing data that multiple functions in the same request might need. It is created fresh for every new request and discarded at the end. Common uses: storing the current authenticated user after JWT verification in a before_request function, caching a database connection for the request, or sharing a traced request ID. Access it: from flask import g; g.current_user = user. Read it later: user = g.get('current_user', None). The g object is thread/context safe — each request has its own g even in multi-threaded servers. Do not confuse it with the Flask application config (app.config) which persists across requests, or the session which persists across user browser sessions.