By using Cookies we can exchange information between the server and the browser to provide a way to customize a user session, and for servers to recognize the user between requests.

HTTP is stateless, which means all request origins to a server are exactly the same and a server cannot determine if a request comes from a client that already did a request before, or it’s a new one.

Cookies are sent by the browser to the server when an HTTP request starts, and they are sent back from the server, which can edit their content.

Cookies are essentially used to store a session id.

Cookies have a very low limit in the data they can hold, since they are sent back-and-forth for every HTTP request to our server - including requests for assets like images or CSS / JavaScript files.

Cookies have a long history, they had their first version in 1994, and over time they were standardized in multiple RFC revisions.

RFC stands for Request for Comments, the way standards are defined by the Internet Engineering Task Force (IETF), the entity responsible for setting standards for the Internet

The latest specification for Cookies is defined in the RFC 6265, which is dated 2011.

It’s important to know those limitations:

  • Cookies can only store 4KB of data
  • Cookies are private to the domain. A site can only read the cookies it set, not other domains cookies
  • You can have up to 20 limits of cookies per domain (but the exact number depends on the specific browser implementation)
  • Cookies are limited in their total number (but the exact number depends on the specific browser implementation). If this number is exceeded, new cookies replace the older ones.

Cookies can be set or read server side, or client side.

In the client side, cookies are exposed by the Document object as document.cookie

Lessons in this unit:

0: ▶︎ Introduction
1: Setting cookies
2: Setting a cookie expiration date
3: Setting a cookie path
4: Setting a cookie domain
5: Cookies security
6: Updating a cookie
7: Deleting a cookie
8: Accessing the value of a cookie
9: Checking if a cookie exists
10: Inspecting cookies