The primary difference between sessions and cookies lies in where the data is stored and how it’s managed. A session is server-side storage, meaning all the user’s data is stored on the web server, with a unique session ID sent to the user’s browser. This ID is used to retrieve session data for that specific user. In contrast, cookies are client-side storage, saved directly in the user’s browser. They can persist data across multiple sessions or websites if configured that way.
Sessions are generally more secure since the sensitive data remains on the server, while cookies are susceptible to tampering or interception. However, cookies are more efficient for storing small, non-sensitive information like user preferences or site behavior tracking.