HTTP Cookie

An HTTP cookie, often simply referred to as a cookie, is a small text file created by a website that is stored on the user’s computer. It contains information, including settings or data, that enables the website to recognize the user on subsequent visits.  

What is an HTTP cookie used for?

HTTP cookies are small text files that websites store on users’ terminal equipment to perform various functions and optimize the browsing experience. One of the main uses of cookies is session management. They enable websites to keep track of a user’s login status so that the user does not have to re-enter their credentials each time they visit a new page.  

Another important use is personalization. Cookies store user settings, such as preferred language or layout preferences, to improve the user experience. In addition, cookies are used for tracking and analysis. They enable website operators to analyze user behavior in order to optimize content and provide personalized advertising.  

In online shops, cookies play a central role in the shopping cart function. They store the items that a user has placed in the shopping cart, even if they leave the page and return later. Finally, certain cookies also serve security purposes. They help to implement security features by, for example, detecting unauthorized login attempts.  

What types of HTTP cookies are there?

• Session cookies only exist during a browser session and are deleted as soon as the browser is closed. They store temporary information, such as the contents of a shopping cart in an online store. 
• Persistent cookies remain stored on the end device for a specified period of time, even after the browser has been closed. They enable websites to remember login information or language settings in order to provide users with a consistent experience on future visits. 
• First-party cookies are set directly by the visited website and are mostly used to improve the user experience; for example, by saving preferences or login information. 
• Third-party cookies come from external services or advertising networks that are integrated into the visited website. They are often used for tracking and marketing purposes to analyze surfing behavior across different websites. 
• Necessary cookies are essential for the basic functions of a website, such as navigation or access to protected areas. Without these cookies, the website cannot function properly. 
• Functional cookies enable the website to provide advanced features and personalization, such as storing language settings or preferred layouts. 
• Performance cookies collect information about how visitors use the website in order to improve its performance. They help to optimize page loading times and identify navigation problems. 
• Tracking and advertising cookies are used to analyze users’ surfing behavior and provide personalized advertising. They may collect information about pages visited and links clicked. 

Who stores cookies?

Cookies are created by websites and stored on the user’s device.  

Websites (server-side): When a user visits a website, the web server sends an HTTP header with the command to set a cookie. This cookie contains information that the server needs for future interactions, such as session data or user settings.  

Web browser (client-side): The user’s web browser receives the command from the server and stores the cookie on the local device. When future requests are made to the same website, the browser automatically sends the stored HTTP cookie back to the server, allowing the server to identify the user or provide personalized content.  

In addition, third-party providers that are integrated into a website can also set cookies. These so-called third-party cookies come from external services, such as advertising networks or analysis tools, and are also stored by the user’s browser. 

What data is collected?

HTTP cookies collect different types of data, depending on their purpose and origin.  

• Session information: Cookies store data about the current browser session, such as the contents of a shopping cart in an online store or the login status on a website. 

• Personalization data: To improve the user experience, cookies store preferences such as language settings, preferred layouts, or recently visited pages. 

• Authentication data: Cookies can store login information so that users are automatically logged in on future visits without having to re-enter their access data. 

• Tracking and analysis information: Third-party cookies collect data about surfing behavior, including websites visited, time spent and interactions. This information is often used for marketing purposes and to create user profiles. 

What are the pros and cons of an HTTP cookie?

Cookies provide numerous benefits that make them an essential part of website functionality. They enable a simple and effective method of maintaining session state across the HTTP protocol, which allows for the efficient management of user sessions and the delivery of personalized content. Persistent cookies have the added benefit of being stored on the user’s hard drive, so information such as login details or shopping cart contents are retained even after the browser is closed. This is particularly useful for features such as “Remember Me” or for online stores that allow users to resume their purchases later. 

Another advantage is cross-domain use. Cookies can be shared between different pages and subdomains of the same website, which facilitates the consistent management of user data. For website operators, cookies are also cost-efficient because they enable data storage on the client side, thus reducing the need for server-side storage. This saves hosting costs and improves server performance. In addition, cookies support the execution of A/B tests by presenting users with different versions of a website, which makes it much easier to optimize content and user experiences. 

However, there are also disadvantages. The size and number of cookies per domain are limited by most browsers. A single HTTP cookie usually cannot be larger than 4 KB and no more than 150 http cookies are usually allowed per domain, which limits the amount of storable information. In addition, users can delete cookies at any time via their browser settings. This can be problematic if websites rely heavily on cookies, as important information such as session data or shopping cart contents may be lost. 

Furthermore, cookies pose security and privacy risks. They can contain sensitive information and be a potential target for attacks if they are not properly secured. They can also be used to track user behavior across multiple websites, which can raise privacy concerns. Users can directly cause compatibility issues by disabling cookies or using browser extensions that block them. While users often do this for privacy reasons, it can affect the functionality of websites. Last but not least, website operators face legal challenges because the use of cookies must comply with data protection laws, such as the GDPR.  

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