HTTP is a so called stateless protocol. Wikipedia says:

“In computing, a stateless protocol is a communications protocol that treats each request as an independent transaction that is unrelated to any previous request so that the communication consists of independent pairs of request and response.”

Imagine talking to a person with a very shortlived memory:

That’s what’s meant by HTTP being stateless: The web application just responds to the request at hand, but has no way to identify how these requests relate to each other.

Imagine thousands of users clicking around and using your web application. The application would just respond to each of these requests individually, but does not know from the protocol where these requests are coming from, or how many people (browsers) it is talking to: There is no concept of a conversation, or “session” in HTTP.


However, of course there are ways to identify your users. We all know that we can sign in to a web application, and it would recognize who we are. Right?

When you sign into Gmail it will display your emails, not anyone else’s emails. Obviously it needs to know who you are, so it can find your emails. The same happens for basically every useful, modern web application.

In order to identfy who is making a request web applications often use cookies for this. There are other techniques, but using cookies is by far the most common one.

So let’s check that out.