How can cookies be used in a web application?

Cookies are small pieces of data that are stored by a web browser on a user's device. They are often used to remember user preferences, track user activity, and provide personalized content. In this article, you will learn how cookies can be used in a web application for different purposes and how to manage them securely and efficiently.

1 What are cookies?

Cookies are text files that contain key-value pairs of information. They are created by a web server and sent to a web browser when a user visits a website. The browser then stores the cookies on the user's device and sends them back to the server with every subsequent request. This way, the server can identify the user and customize the response accordingly. For example, a cookie can store the user's name, language, shopping cart, or login status.

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Chi-Chi Ross

Business Development | Enterprise Account Executive
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Internet cookies are used to identify specific users and customize their web browsing experience. The data that is stored in a cookie is created as soon as a connection established with the server. The data in the cookie is labeled with an ID unique to you and your computer. The network server reads this unique ID and is able to customize information served to you.

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Dineth Siriwardana

BICT @ UOR | Flutter | Postman Student Leader | β MLSA
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Cookies like a tiny pocket that we can fill with small items.Web developers must have a solid understanding of cookies, including their uses and limitations.

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2 Why use cookies?

Cookies can be used for various reasons in a web application, such as authentication, personalization, analytics, and marketing. For authentication, cookies can store a token or session ID that verifies the user's identity and grants access to restricted resources. Personalization can be achieved by storing user preferences, such as theme, font size, or location, and displaying content that matches those preferences. Analytics can be provided by storing user behavior, such as pages visited, time spent, or actions performed. Lastly, cookies can store user profiles to deliver targeted ads or offers that are relevant to the user.

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Dineth Siriwardana

BICT @ UOR | Flutter | Postman Student Leader | β MLSA
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One time for a University project we develop a website with HTML , CSS and JS. So we have to save everything on cookies like ( History , Most used items , cart details, Dark or Light Theme ) And most of the time I store user details using an encryption, I encrypt and store all details in a cookie as an array then I can get that details whatever I want

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3 How to create cookies?

Cookies can be created by using the Set-Cookie header in the HTTP response. This header specifies the name and value of the cookie, as well as optional attributes such as Expires, Max-Age, Domain, Path, Secure, and HttpOnly. For example, a cookie named username with the value john can be created with a one hour expiration and HttpOnly flag to restrict access to the server with this header: Set-Cookie: username=john; Expires=Wed, 21 Oct 2020 07:28:00 GMT; HttpOnly . This will ensure that the cookie is deleted by the browser when it expires and can only be accessed by the server.

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Dineth Siriwardana

BICT @ UOR | Flutter | Postman Student Leader | β MLSA
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In JS this is the code document.cookie = "username=DinethSiriwardana; expires=Wed, 09 Nov 2023 12:00:00 UTC; path=/"; I get this example because you have to consider the path. The "path" attribute in a web cookie is used to specify the URL path for which the cookie is valid.

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4 How to read cookies?

Cookies can be read by using the Cookie header in the HTTP request. The header contains a list of all the cookies that are stored by the browser and match the domain and path of the request. For example, the following header sends two cookies named username and language to the server: Cookie: username=john; language=en The server can then parse the header and extract the name and value of each cookie. Alternatively, some web frameworks provide built-in methods or libraries to read and manipulate cookies more easily.

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5 How to delete cookies?

Cookies can be deleted by setting their expiration date to a past date or by setting their max-age attribute to zero. This will instruct the browser to remove the cookies from the device. For example, the following header deletes a cookie named username: Set-Cookie: username=; Expires=Thu, 01 Jan 1970 00:00:00 GMT Alternatively, some web frameworks provide built-in methods or libraries to delete cookies more easily.

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6 How to secure cookies?

Cookies can contain sensitive or personal information that should be protected from unauthorized access or modification. To ensure their security, it's important to use HTTPS for encryption, as well as the Secure and HttpOnly attributes to prevent the cookies from being sent over insecure connections or accessed by client-side scripts. Additionally, the SameSite attribute helps prevent cross-site request forgery (CSRF) attacks. Lastly, encryption or hashing can obscure the content of the cookies to prevent unauthorized reading or writing.

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Christos Soulaki

Head of Development @ Creative Mules | Creative Developer | Mentor
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Although cookies are mostly used for marketing purposes or web apps, they can also be used on websites to show a longer loader the first time, show a modal once every x days, or even show/hide elements based on certain conditions. Although local storage is a great option for storing some state, cookies are great for when you need to add an expiration date for an event

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How can cookies be used in a web application?

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1 What are cookies?

2 Why use cookies?

3 How to create cookies?

4 How to read cookies?

5 How to delete cookies?

6 How to secure cookies?

7 Here’s what else to consider

Web Development

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How can cookies be used in a web application?

1

2

3

4

5

6

7

1 What are cookies?

2 Why use cookies?

3 How to create cookies?

4 How to read cookies?

5 How to delete cookies?

6 How to secure cookies?

7 Here’s what else to consider

Web Development

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