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The Facts About Web Cookies and How to Control Them

Cookies track how users browse the Internet, and they can be limited on your machine

By Federal Trade Commission
February 15, 2012

Have you ever wondered why some online ads you see are targeted to your tastes and interests, or how websites remember your preferences from visit to visit? The answer may be in the “cookies.”

A cookie is information saved by your Web browser, the software program you use to visit the Web. Cookies can be used by companies that collect, store and share bits of information about your online activities to track your behavior across sites. Cookies also can be used to customize your browsing experience or to deliver ads targeted to you.

Here are answers to some commonly asked questions about cookies, what they are, what they do and how you can control them.

Understanding Cookies

What is a cookie?

A cookie is information that a site saves to your computer using your Web browser. A cookie allows sites to record your browsing activities, like what pages and content you've looked at, when you visited, what you searched for, and whether you clicked on an ad. Data collected by cookies can be combined to create a profile of your online activities.

Who places c­ookies on the Web?

First-party cookies are placed by a site when you visit it. They can make your experience on the Web more efficient. For example, they help sites remember:

  • Items in your shopping cart.
  • Your log-in name.
  • Your preferences, like always showing the weather in your home town.
  • Your high game scores.

Third-party cookies are placed by someone other than the site you are on. These may include an advertising network or a company that helps deliver the ads you see. They may be used to deliver ads tailored to your interests. For example, if you read an article online about running, a cookie may be used to note your interest in running, and add that to a profile. And you may see coupons to save money on running shoes.

Controlling Cookies

How can I control cookies?

Various browsers have different ways to let you delete cookies or limit the kinds of cookies that can be placed on your computer. When you choose your browser, you may want to consider which suits your privacy preferences best.

To check out the settings in a browser, use the "Help" tab or look under "Tools" for settings like "Options" or "Privacy." From there, you may be able to delete cookies, or control when they can be placed. Some browsers allow add-on software tools to block, delete or control cookies. And security software often includes options to make cookie control easier.

If you disable cookies entirely, you may limit your browsing experience. For example, you may need to enter information repeatedly or you might not get personalized content or ads that are meaningful to you. However, most browsers’ settings will allow you to block third-party cookies without also disabling first-party cookies.

What are “opt-out” cookies?

Some websites and advertising networks have cookies that tell them not to use information about what sites you visit to target ads to you.

There are a couple of ways to opt out of certain types of data collection or certain kinds of targeted advertising:

  • You can download software an “add-on” to your browser that controls whether and how cookies including opt-out cookies are stored or deleted. You can find add-ons on sites sponsored by the browser. Look through the settings or “Help” function. Browser companies review most add-ons for security and functionality before making them available for download, but as with any software, don’t download an add-on unless you have checked it out and trust the source.
  • Programs from the online advertising industry, including The Network Advertising Initiative and the Digital Advertising Alliance, offer tools for opting out of targeted advertising often by placing opt-out cookies offered by their members. You also can opt out by visiting advertising networks and advertiser websites one by one.

Deleting all your cookies will erase any opt-out cookies you’ve downloaded. To restore opt-out cookies, you will have to go through the opt-out procedure again.

Cookies are used for many purposes for example, to limit the number of times you’re shown a particular ad. So even if you opt out of targeted advertising, a company may still use cookies for other purposes.

Private Browsing


What's private browsing?

Many browsers offer private browsing settings that are meant to let you keep your Web activities hidden from other people who use the same computer. With private browsing turned on, your browser won't retain cookies, your browsing history, search records or the files you downloaded. Privacy modes aren't uniform, though; it's a good idea to check your browser to see what types of data it stores. Although it won't keep cookies after the private browsing session ends, cookies used during the private browsing session can communicate information about your browsing behavior to third parties.

Flash Cookies

What are Flash cookies?

A Flash cookie is a small file stored on your computer by a website that uses Adobe's Flash player technology. Flash cookies use Adobe's Flash player to store information about your online browsing activities. Flash cookies can be used to replace cookies used for tracking and advertising, because they also can store your settings and preferences. When you delete or clear cookies from your browser, you won't necessarily delete the Flash cookies stored on your computer.

Can I control Flash cookies?

The latest versions of Google Chrome, Mozilla Firefox and Microsoft Internet Explorer let you control or delete Flash cookies through the browser's settings. If you use an older version of one of these browsers, upgrade to the most recent version and set it to update automatically.

Like regular cookies, deleting Flash cookies gets rid of the ones on your computer at that moment. Flash cookies can be placed on your computer the next time you visit a website or view an ad unless you block Flash cookies altogether.

New Technologies

Are there other tracking technologies I should know about?

New technologies are constantly emerging, and some can be used to track your online activities even if you control regular cookies. These are generally referred to as "supercookies." If companies offer you an opt out, they need to respect your preference, whether they use supercookies or regular cookies.

What is "Do Not Track"?

Do Not Track is a tool that allows you to express your preference not to be tracked across the Web. Turning on Do Not Track through your Web browser sends a signal to every website you visit that you don't want to be tracked. Companies then know your preference. If they have committed to respect your preference, they are legally required to do so.

Some browsers already support Do Not Track. If you want to use Do Not Track, check to see if the browser you use offers it or use a browser that does.

By Federal Trade Commission
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