Cookies are small files that websites store on your device to remember information about you
A cookie is a text file — usually just a few kilobytes — that a website saves to your computer or phone. It contains data the website wants to remember: your login information, items in your shopping cart, your language preference, or a record that you visited. When you return to that website, your browser reads the cookie and sends it back, so the site knows who you are and what you were doing.
Cookies are not programs. They cannot run code, steal files, or damage your device on their own. They are just stored text, like a note a restaurant writes down about your usual order. The website that created the cookie is the only one that can read it — your browser keeps them separated by website.
Without cookies, every time you visited a website you would be a stranger. You would have to log in again, your shopping cart would be empty, and the site would have no memory of your preferences. Cookies make the web feel continuous instead of starting over each time.
Key Takeaways
- Cookies are small text files stored on your device that let websites remember information about you between visits.
- First-party cookies come from the website you are visiting; third-party cookies come from advertisers or analytics companies and track you across multiple sites.
- Your browser stores cookies in a folder on your device, and you can view, delete, or block them in your browser settings.
- Cookies cannot run programs or steal files, but third-party cookies do allow companies to build a profile of your browsing habits.
- Clearing cookies will log you out of websites and reset your preferences, but it does not prevent new cookies from being created when you visit sites again.
First-party cookies versus third-party cookies
A first-party cookie is created by the website you are actually visiting. When you log into your email, the email site creates a cookie that stores your session information. When you add items to a shopping cart, the store creates a cookie that remembers what you picked. These cookies only work on that one website — Amazon cannot read a cookie that Netflix created.
A third-party cookie is created by a different company than the one running the website you are on. An advertising network like Google or Meta might place a cookie on your device when you visit a news site, even though you did not go to Google or Meta directly. That cookie tracks which sites you visit, what you click on, and what you search for. The advertiser uses this profile to show you targeted ads across many different websites.
Third-party cookies are why you see ads for something you looked at once, weeks later, on a completely different site. The advertiser's cookie followed you there. First-party cookies are why you stay logged into your email — they are necessary for the site to work. Third-party cookies are optional and exist mainly to track your behavior for profit.
How your browser stores and manages cookies
Your browser — Chrome, Firefox, Safari, or Edge — stores cookies in a folder on your device. On Windows, this folder is usually buried in your user profile. On Mac, it is in the Library folder. You do not need to find it manually; your browser has a settings menu that shows you all your cookies.
In Chrome, go to Settings, then Privacy and Security, then Cookies and Other Site Data. You will see a list of every website that has stored a cookie on your device. You can delete all of them at once, delete cookies from a single site, or set rules for which sites are allowed to store cookies. Firefox, Safari, and Edge have similar menus with slightly different names.
When you clear your cookies, you are deleting the stored files. This will log you out of websites, reset your preferences, and remove the tracking data that advertisers have collected. However, clearing cookies does not prevent websites from creating new ones the next time you visit. The cookie is created fresh each time unless you have set your browser to block them.
Session cookies versus persistent cookies
A session cookie exists only while you are using a website. It is stored in your browser's memory, not on your hard drive. When you close the browser tab or shut down your computer, the session cookie disappears. Most login cookies are session cookies — they keep you logged in while you are actively using the site, then vanish when you leave.
A persistent cookie stays on your device even after you close the browser. It has an expiration date set by the website — it might last a few days, a few months, or a year. Persistent cookies are what remember your preferences the next time you visit: your language choice, your theme setting, or the fact that you do not want to see a welcome banner again. Advertisers also use persistent cookies to track you across visits and across different websites.
You cannot always tell which type of cookie a website is creating just by using it. Your browser settings let you see the expiration date of each cookie, which tells you whether it is session or persistent. Cookies that expire "at end of session" are session cookies; cookies with a future date are persistent.
Why websites use cookies and what they track
Websites use cookies for practical reasons: to keep you logged in, to remember your settings, to store items in your cart, and to track how many people visit and what they do there. A news site uses cookies to count unique visitors and see which articles get read most. A store uses cookies to remember what you looked at so it can suggest similar items next time.
Advertisers use cookies to build a detailed profile of your interests and behavior. They track which sites you visit, how long you stay, what you search for, what you click on, and what you buy. This data is valuable because it lets them show you ads that are more likely to work. A cookie from an ad network might know that you visited three car websites, read articles about electric vehicles, and clicked on a Tesla ad — so the next time you see an ad, it will be for electric cars.
Some websites also use cookies to track you for security reasons: to detect fraud, to notice if someone else is trying to log into your account, or to enforce rate limits on automated requests. These cookies are usually necessary for the site to function safely.
How to control cookies in your browser
Most browsers let you choose one of three approaches to cookies. The first is to accept all cookies — this is the default on most browsers, and it means websites and advertisers can track you freely. The second is to block all cookies — this will break many websites because they cannot function without at least first-party cookies. The third is to block third-party cookies only, which is a middle ground: you stay logged in and your preferences are saved, but advertisers cannot track you across sites.
To change your cookie settings in Chrome, go to Settings, then Privacy and Security, then Cookies and Other Site Data. You will see options to block all cookies, block third-party cookies, or allow all. You can also add specific websites to an allow list or block list — for example, you might block third-party cookies everywhere but allow them on a site you trust.
Firefox and Safari have similar controls. In Firefox, go to Settings, then Privacy and Security, and look for the Cookies and Site Data section. In Safari on Mac, go to Preferences, then Privacy, and choose which cookies to accept. On iPhone and iPad, Safari's cookie settings are in Settings, then Safari.
You can also use browser extensions that block cookies or trackers. Popular options include uBlock Origin, Privacy Badger, and Ghostery. These extensions go further than built-in browser settings — they block known tracking scripts and cookies from thousands of advertisers and data brokers. However, they can sometimes break websites that rely on those scripts to function.
The difference between cookies and other tracking methods
Cookies are not the only way websites track you. Local storage and session storage are similar to cookies but can hold much more data — up to several megabytes instead of a few kilobytes. Pixels and beacons are tiny invisible images that websites embed in pages or emails; when you load the page or open the email, your browser requests the image, and the server records that you viewed it. Fingerprinting is a technique that identifies you by collecting information about your device: your browser type, screen resolution, installed fonts, and other details that together are usually unique.
Advertisers and data brokers use all of these methods together. Even if you block cookies, a website might use local storage or fingerprinting to recognize you. Even if you use a private browsing mode, which does not store cookies, a pixel in an email can still track whether you opened it. Blocking cookies is useful, but it is only one part of protecting your privacy online.
Frequently Asked Questions
Can cookies give a website access to my files or passwords?
No. A cookie is just a text file that the website created and stored. It cannot read your files, access your passwords, or run programs. However, if a cookie contains your login token — the temporary code that keeps you logged in — and someone steals that cookie, they could use it to log in as you. This is why using HTTPS (the find version of websites) is important: it encrypts cookies so they cannot be intercepted.
What happens if I block all cookies?
Many websites will not work properly. You will be logged out constantly, your shopping cart will empty, and sites will not remember your preferences. Some sites will refuse to load at all. Blocking third-party cookies only is usually a better choice — it keeps sites functional while stopping most advertising tracking.
Do private browsing or incognito mode prevent cookies?
Private browsing mode does not prevent websites from creating cookies — it just deletes them when you close the window. While you are browsing, websites and advertisers can still track you with cookies. The difference is that the cookies are not saved to your device afterward. Advertisers can still use other methods like pixels and fingerprinting to track you even in private mode.
If I clear my cookies, will websites stop tracking me?
Clearing cookies removes the tracking data that was stored, but it does not prevent new cookies from being created. The next time you visit a website, it will create a new cookie and start tracking again. To actually stop tracking, you need to block third-party cookies in your browser settings or use a tracking blocker extension.
Why do some websites ask for permission to use cookies?
In Europe, the General Data Protection Regulation (GDPR) requires websites to ask for permission before storing cookies that are not strictly necessary. In other regions, websites often ask as well because it builds trust. The cookie banner you see is usually asking permission for third-party cookies and analytics — first-party cookies that make the site work are usually allowed without asking.