Client-side Sessions in Flask

Sessions in Flask can be considered "client-side", as sessions are stored client-side in browser cookies.


  1. Validating and creating sessions is fast (no data storage)
  2. Easy to scale (no need to replicate session data across web servers)


  1. Sensitive data cannot be stored in session data, as it’s stored on the web browser
  2. Session data is limited by the size of the cookie (usually 4 KB)
  3. Sessions cannot be immediately revoked by the Flask app

For more, review Sessions in Flask.