When should I use session variables instead of cookies?

Question

Session variables and cookies seem very similar to me. I understand the technical differences, but how do you decide when to use one vs. the other?

Answer 1

Sessions and cookies are not the same at all. Cookies are client side. Sessions are server side. Sessions often (but not necessarily) use cookies to correlate one request with another from the same user to identify that they belong to the same session.

A session is an artificial concept, and HTTP doesn't have that notion. It is created by web servers to help web developers carry information across requests, like user account information, shopping carts, form data, etc. A cookie is carried by standard HTTP headers.

The information you store in a session vs. a cookie is up to you. Typically you put stuff in cookies that you want to persist across sessions after the user closes his/her browser. Maybe remembering authentication tokens to implement "remember me" functionality, or past user activity to personalise his/her experience. Keep this information small and "referential", i.e. it could be just IDs that refer to richer information you store sever side. Remember that what is client side is more vulnerable to malware, so don't store passwords or sensitive information.

Finally, there is also local storage, which you did not mention. This is also client side, but arguably a bit less susceptible to cross-site scripting hacks since, unlike cookies data, it is not automatically sent in the headers.

Answer 2

Cookies can persist longer than a single session. However, cookies may also be deleted by the user, or you may have a user whose browser does not accept cookies (in which case only a server-side session will work).

Answer 3

• Always use sessions
• Use cookies only if you need longer logged-in sessions - Then add a cookie with an encrypted user ID.

Answer 4

Your definite Guide

N.B - A cookie is stored on users' browsers, and a session is stored on your hosting server machine.

When to Use

1. Use a cookie when you want your application to remember user's data always, even when they have closed their browsers. E.g whenever you type www.facebook.com it takes you to your account, even when your browser has been closed and re-opened.

   Because any data kept in a session is cleared off once you close your browser.

2. Use a cookie when the user information to be stored is much larger than normal. ... With a session, if you have a larger user base, like Facebook, think of how it will look storing all user sessions on the hosting machine.

3. Use a session when the user information to be stored is not larger than normal, and you don't want the public to have access to your user variables...

Answer 5

Most of the time, session state is persisted using cookies. So it's not really a question of one or the other, but how to use them together.

Using your framework's session infrastructure may make things easier, but tracking state manually with cookies usually gives you finer grained control. The correct solution depends on what you're trying to accomplish.

Answer 6

Cookies are sent to the server on every request, so if you plan to store a fair amount of data, store it in a session.

Otherwise, if you are storing small amounts of data, a cookie will be fine.

Any sensitive data should be stored in a session, as cookies are not 100% secure. An advantage of cookies is that you can save memory on your server that would normally be storing session data.