What are computer cookies?

A computer cookie, also known as an “HTTP cookie”, is a small text file containing a unique ID tag, placed on a user’s computer by a website. In this file, various information can be stored, from pages visited on the website, to information voluntarily provided to the website. These tiny files provide practical benefits to website users and operators and often make browsing the Internet a smoother experience than it would otherwise be. However, privacy advocates tend to be wary of them, as many users don’t know exactly what information is collected and how the information might be used or shared.

Permanent computer cookies are stored for a long time on the user’s hard drive.

Types of Cookies

There are two types of computer cookies: temporary and permanent. Temporary cookies, also called session cookies, are stored for a short period and removed as soon as the browser is closed. Permanent cookies, also called persistent cookies, are stored for a long time on the user’s hard drive and, if deleted, will be replaced the next time the respective website is visited.

The temporary cookie is very simple. It works by reserving some of the browser’s cache memory to retain information about the user’s activities during their visit. After placing a selected purchase in a shopping cart, for example, the user can continue to search the site for additional products without having to go through a separate checkout for each item. Once the browser is closed, however, all temporary cookies are lost. Return surfers are not recognized, shopping carts are empty and any other forms or information will have to be re-entered.

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On the other hand, permanent cookies make it possible for a website to recognize a surfer on an ongoing basis. This is done by transferring a text file with a unique identification tag to the visitor’s hard drive, while maintaining a corresponding file on the server. On subsequent visits, the browser automatically delivers this cookie, allowing the website to instantly retrieve the corresponding file. Persistent cookies can last for years unless deleted, or until the cookie’s internally defined lifetime has passed. Today, permanent cookies are the most common type of cookie used.

How cookies are used

At its most basic level, a website uses computer cookies to record when an individual visits, which pages are viewed and how long the visitor stays. If it returns at a later date, the visitor’s cookie triggers the record of previous visits and corrects it to include what happened during the new visit. If any personal information is made available in any of these visits, it will be instantly associated with the “anonymous” identifier and, consequently, with the entire profile. That way, a website can more easily monitor changing trends and other statistics among its visitors. Over time, persistent cookies have also resulted in some initially unexpected uses, such as web profiling.

Marketers have developed a substantially broader application for cookie profiling. Having advertising rights on many of the most popular websites, merchants are now able to pass third-party cookies to Internet users. This allows them to recognize individuals as they travel between different sites, recording comprehensive profiles of people’s browsing habits over a period of months or even years. Sophisticated profiling programs quickly classify the information provided by computer cookies, categorizing targets into several different areas based on statistical data. Age, income level and even sexual orientation can often be determined with varying degrees of accuracy through cookie profiles, along with many other characteristics. Much depends on how much a person surfs and where they choose to go online.

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As a result of public outcry in response to hidden profiling, cookie controls are now included in web browsers to allow users to turn cookies off — options that were not available in 1995 when permanent cookie technology was first introduced. Cookie controls also allow user-created lists for exceptions, so that a user can turn most cookies off, for example, but allow them from sites where computer cookies are put to a desired purpose. Third-party cookies often have their own controls, as they are normally placed by marketers.


As a concept, the computer cookie dates back to 1994. In that year, it was adapted as a tool for the World Wide Web by Leo Montulli from a similar technique, called “magic cookie,” which was used in UNIX® systems. This is also the origin of the term itself. It was not for another couple of years, however, that the cookies became widely known to the general public. In 1996, articles about them began appearing in the mainstream press, many of which raised concerns about privacy, and in turn inspired the changes in web browsers that ultimately gave users more control over how cookies were implemented on their individual machines.

Are Cookies Dangerous?

In and of themselves, computer cookies are not malicious; they generally make surfing more seamless, and help websites operate more profitably and with greater efficiency. There are legitimate concerns, however, about the ways that cookies can be used to follow users from one site to another, forming comprehensive profiles. Some consider this to be a violation of privacy, and in the wrong hands the information can potentially be exploited for questionable purposes. Much akin to managing the privacy settings on social networking sites, however, each user has the power to decide for himself whether to accept cookies, whether to block certain types, and how often to purge them. Most modern browsers, as well as many Internet security products, give users easy and flexible control over all of these decisions. Many websites detail their cookie process, if any, in their privacy policy.

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