What cookies are and what they do
A cookie is a small file that a website stores on your computer or phone. It contains information the website wants to remember about you — your login details, what you put in your shopping cart, your language preference, or what you clicked on last time you visited. When you go back to that website, your browser automatically sends the cookie back, and the website reads it to remember who you are and what you were doing.
Cookies are not programs that run on your device. They cannot install software, steal passwords, or access files outside the website that created them. They are just text files, usually a few kilobytes in size. A website can only read cookies it created itself — a cookie from Amazon cannot be read by Netflix or by any other site.
Your browser stores cookies in a dedicated folder. You can see them, delete them, or block new ones from being created. Different browsers handle cookies differently, and you have control over what happens to them.
Key Takeaways
- Cookies are small text files websites store on your device to remember information about you, like your login or shopping cart contents.
- 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.
- You can delete cookies anytime, block them entirely, or allow only certain types — the setting is in your browser preferences.
- Cookies expire on a date set by the website, ranging from when you close your browser to years in the future.
- Websites must tell you they use cookies and get your permission in most countries, usually through a banner at the top of the page.
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 login session. When you add something to your cart on a shopping site, that site creates a cookie to remember what you picked. These cookies make the website work better for you and are generally considered less invasive because only that one website can read them.
A third-party cookie is created by a different company — usually an advertiser or analytics service — and placed on the website you are visiting without you directly interacting with that company. For example, a clothing retailer might use Google Analytics to track how many people visit their site and what they click on. Google creates a cookie on your device that follows you across many different websites. This is how you see an ad for shoes on one website, then see the same shoe ad on a completely different website later. The advertiser is using the cookie to track your browsing across the internet.
Third-party cookies are what most people mean when they talk about websites "tracking" them. Because they follow you from site to site, they build a profile of your interests and browsing habits. Many browsers now block third-party cookies by default, and some countries have restricted how they can be used.
How cookies get created and sent back
When you visit a website, the site's server sends you a message that says "store this cookie on your device." Your browser reads that message and creates a small file in its cookies folder. The message includes the cookie's name, its contents, and when it should expire.
Every time you visit that website again, your browser automatically includes that cookie in the request it sends to the server. The server reads the cookie and knows it is you — or at least, it knows it is the same device that visited before. If the cookie contains your login information, you stay logged in. If it contains your language preference, the site shows you pages in that language without asking again.
The whole process happens in the background. You do not see the cookie being created or sent. Your browser handles it automatically, which is why cookies work so smoothly — you do not have to do anything to make them function.
When cookies expire and how to delete them
Cookies have an expiration date set by the website that created them. Some cookies expire when you close your browser — these are called session cookies and are typically used for login information. Other cookies stay on your device for months or years — these are called persistent cookies and are used to remember preferences or track behavior over time.
You can delete cookies manually anytime. In most browsers, you can go to Settings or Preferences, find the Privacy or History section, and choose to clear cookies. You can delete all cookies at once, or delete cookies from specific websites. When you delete a cookie, the website no longer has that information about you — the next time you visit, it will not remember you unless you log in again.
You can also set your browser to delete cookies automatically when you close it, or to block certain types of cookies entirely. Most browsers let you allow cookies from the website you are visiting but block third-party cookies from advertisers. Some browsers have a "Do Not Track" setting that sends a signal to websites asking them not to track you, though not all websites honor this request.
Why websites use cookies and what they track
Websites use cookies for practical reasons: to keep you logged in, to remember what you put in your shopping cart, to store your preferences like dark mode or language, and to remember what you have already read so they do not show you the same article twice. These uses make websites faster and more convenient for you.
Websites also use cookies to track your behavior — what pages you visit, how long you stay, what you click on, and what you search for. They do this to understand how people use their site, to improve the design, and to show you ads based on your interests. A news site might use cookies to see which articles are most popular. An online store might use cookies to see which products people look at but do not buy.
Advertisers use third-party cookies to build a profile of your interests across many websites. This profile is valuable because it lets them show you ads for things you are actually interested in, rather than random ads. But it also means your browsing habits are being tracked and sold to companies you have never heard of.
Cookie consent and privacy laws
In the European Union, the United Kingdom, and many other countries, websites must tell you they use cookies and get your permission before storing them. This is why you see a banner at the top or bottom of many websites asking you to accept cookies. The banner usually has buttons for "Accept All," "Reject All," or "Customize" — the customize option lets you choose which types of cookies you allow.
These laws require websites to be transparent about what cookies do and who can access the information they collect. In the United States, there is no single federal cookie law, but some states like California have privacy laws that give you the right to know what data is collected and to ask companies to delete it.
If a website does not show you a cookie consent banner, it may not be required to by law in that country, or it may be ignoring the law. You can still control cookies yourself through your browser settings regardless of what the website says.
How to manage cookies in your browser
Every major browser — Chrome, Firefox, Safari, and Edge — lets you control cookies through settings. In Chrome, go to Settings, then Privacy and Security, then Cookies and Other Site Data. You can choose to allow all cookies, block all cookies, or block only third-party cookies. You can also see a list of all cookies stored on your device and delete specific ones.
Firefox has similar controls under Settings, Privacy and Security, Cookies and Site Data. Safari on Mac and iPhone lets you manage cookies under Settings, Privacy. Edge uses the same controls as Chrome because it is built on the same engine.
You can also use browser extensions that block cookies or trackers. Popular options include uBlock Origin, Privacy Badger, and Ghostery. These extensions block many third-party cookies and trackers automatically, though they may break some websites that rely on them to function.
If you want maximum privacy, you can set your browser to delete all cookies when you close it. The downside is that you will have to log in to websites every time you visit, and sites will not remember your preferences. A middle ground is to allow cookies from websites you trust but block third-party cookies from advertisers.
Frequently Asked Questions
Can a cookie steal my password or credit card number?
No. A cookie cannot access information you have not given to that specific website. If you enter your credit card number on a shopping site, that site might store it in a cookie, but a cookie from that site cannot reach into your email or bank account. A cookie from one website cannot be read by another website. However, if a hacker breaks into a website's server, they could steal the cookies stored there, which is why websites encrypt sensitive information.
What is the difference between cookies and tracking pixels?
A tracking pixel is a tiny invisible image that websites embed in pages or emails. When you view the page or open the email, your browser downloads the pixel, and the company that owns it learns you viewed that page or email. Pixels do not store information on your device the way cookies do — they just send information back to the company's server. Advertisers use pixels alongside cookies to track you across the internet.
If I delete my cookies, will websites know I deleted them?
No. When you delete a cookie, it is gone from your device, and the website has no way to know you deleted it. The next time you visit, the website will not see the old cookie — it will just create a new one. Websites cannot detect what you do with your browser or files on your device.
Why do some websites stop working when I block cookies?
Some websites rely on cookies to function. If you block all cookies, you may not be able to log in, stay logged in, or use shopping carts. This is usually because the website uses session cookies to keep track of who you are. You can usually fix this by allowing cookies from that specific website while still blocking third-party cookies from advertisers.
Do I need to delete cookies regularly?
Not necessarily. Cookies take up very little space on your device. Deleting them regularly does not speed up your browser or free up meaningful storage. You might delete cookies if you want to clear your browsing history, if you are using a shared computer, or if you want to reset your relationship with a website. Otherwise, letting them accumulate does not cause problems.