What are cookies? how to work?

Many websites use small strings of characters called cookies to store persistent client-side state between connections. The following article will introduce you to cookies and briefly understand how they work. I hope it will be helpful to you.

What are cookies?

Cookies are small files that are stored on the user's computer. They are used to hold a modest amount of data specific to a particular client and website, and can be accessed via the web server or client computer.

Cookies are basically small documents that contain information about the website we browse (settings, records, etc.). For example, when we select the language in which we want to view a website, the website saves the information in a file called a cookie on our computer. The next time we visit the website, it will be able to read the previously saved cookie file (which contains The language of the set website). This way we can view the website in the preferred language without having to select the language again.

The information contained by cookies can be of any type, such as the time the website was visited, items added to the shopping basket, all links clicked on the website, etc.

If a cookie is created in a specific website and you later visit another website, the latter will not be able to read the content from the first website, in other words, only the same website where the information was saved will be accessible.

How do cookies work?

Cookies are passed from the server to the client and back in the HTTP headers of requests and responses. Servers can use cookies to indicate session IDs, shopping cart contents, login credentials, user preferences, etc. Let's take a look at how Cookies work.

As you can see from the above figure, when the user requests a page for the first time, the server sends the cookie object together with the resource to be stored on the client. This object may contain details of the request. Now later, if the user requests the same resource again, it sends the request along with the stored cookie which can be used by the server to further enhance the user's experience.

Two types of Cookies

Session Cookie:

Session cookie means no The state of a defined life cycle, which only persists while the user is using the website, and the session cookie is usually deleted when the web browser is exited. If the user does not visit the website for a while on the server (idle timeout), the session cookie will expire. If someone comes to use our computer, they won't be able to see anything on a website that uses a session cookie because they will need to enter their username and password again.

Persistent Cookie:

Persistent cookie is the state when its life cycle is set. Persistent Cookie is more persistent than the user session. If you set the maximum age of a persistent cookie to 1 year, then within a year, every time the user visits the server, the initial value set in the cookie will be sent back to the server. This can be used to record important information, such as how a user originally arrived at the website. Therefore, persistent cookies are also called tracking cookies.

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