Difference Between Cookies and Sessions

Are you confused about the difference between cookies and sessions?

In today’s digital age, these terms are commonly used in web development and online user experience, but understanding their distinct functionalities is crucial.

Cookies and sessions are both used to store information, but they serve different purposes.

While both cookies and sessions serve similar purposes, they have some key differences that make them more suitable for certain types of applications.

Cookies and sessions are two common mechanisms used by web developers to store user data and maintain user state between requests.

In this article, we’ll explore the difference between cookies and sessions, their advantages and disadvantages, and their use cases, helping you better understand these essential web development concepts.

Storage of cookies and Sessions

One of the main difference between cookies and sessions is where the data is stored.

Cookies are stored on the client side, while sessions are stored on the server side. This means that cookies are typically easier to implement and require less server-side storage, but can also be less secure since they can be modified or deleted by the client.

Sessions, on the other hand, are typically more secure since the session data is stored on the server side, but can require more server-side storage and management.

How long does the data persist?

Another major difference between cookies and sessions is the time data persist.

Cookies can have an expiration date, after which they are no longer valid, but can also be set to last indefinitely.

Sessions, on the other hand, typically expire after a set period of time or when the user logs out. This means that sessions can be used to store more sensitive data that needs to be cleared after a certain amount of time, while cookies are better suited for storing data that needs to persist across multiple visits.

Learn about Cookie and Session in the below sections.

What is a Cookie?

In JavaScript, a cookie is a small piece of data that a website can store on a user’s computer through the user’s web browser. Cookies are commonly used to store user preferences, login information, and other data that the website can use to personalize the user experience.

Cookies are sent from the server to the client in the form of HTTP headers and are stored on the client’s computer in a text file. When the user visits the website again, the browser sends the cookies back to the server along with any requests, allowing the server to access the information stored in the cookies.

Here’s an example of how to create a cookie in JavaScript:

// Set a cookie with a name, value, and expiration date
document.cookie = 'username=john_doe; expires=Thu, 17 Mar 2024 12:00:00 UTC; path=/';

In this example, we set a cookie named username with the value john_doe and an expiration date of March 17, 2024. The path attribute specifies the URL path for which the cookie is valid. If no path is specified, the cookie will be valid for the current page only.

Here’s an example of how to retrieve the value of a cookie in JavaScript

// Get the value of a cookie
const cookies = document.cookie.split('; ');
for (let i = 0; i < cookies.length; i++) {
  const parts = cookies[i].split('=');
  if (parts[0] === 'username') {
    const username = parts[1];
    console.log(`Hello, ${username}!`);
    break;
  }
}

In this example, we split the document.cookie string into individual cookie key-value pairs using split('; '). We then loop through the pairs and split each one into a key and value using split('='). Finally, we check if the key matches username and, if it does, extract the value and log a greeting to the console.

It’s worth noting that cookies can have security implications, as they can be used to track a user’s browsing behavior across multiple websites. As a result, many browsers provide controls to limit or block the use of cookies, and web developers should be careful to use cookies only when necessary and to handle sensitive data appropriately.

What is a Session?

In JavaScript, a session is a way to store user data on the server side between HTTP requests. Sessions are commonly used to maintain user authentication status, track user activity, and store temporary data that needs to be accessed across multiple pages or requests.

When a user logs in to a website, for example, the server may create a new session for that user and associate it with a unique session ID. The session ID is typically stored in a cookie on the user’s computer, and is used to retrieve the session data from the server on subsequent requests.

Here’s an example of how to create a new session in JavaScript:

// Start a new session and set a session variable
req.session.username = 'john_doe';

In this example, we use the req.session object to set a new session variable named username to the value john_doe.

The req object represents the HTTP request being made to the server, and the session object is a property of the req object that provides access to the current user’s session data.

Here’s an example of how to retrieve the value of a session variable in JavaScript:

// Get the value of a session variable
const username = req.session.username;
console.log(`Hello, ${username}!`);

In this example, we use the req.session object to retrieve the value of the username session variable and log a greeting to the console.

It’s worth noting that sessions typically require some form of server-side storage, such as a database or file system, to persist session data between requests.

As a result, implementing sessions can be more complex than using cookies alone, and may require additional server-side code and configuration.