What cookies do
A cookie is a small file that a website stores on your computer or phone. When you visit that website again, your browser sends the cookie back to it automatically. The website reads what's in the cookie and remembers things about you — what you looked at, what you put in your shopping cart, whether you logged in, what language you prefer.
Cookies exist because the internet was built without memory. Each time your browser asks a server for a page, the server has no idea who you are or what you did five minutes ago. Cookies bridge that gap. Without them, you would have to log in to your email every single time you clicked a link, or a store would forget what you put in your cart the moment you went to another page.
The cookie itself is just text — usually a string of letters and numbers, sometimes a few hundred characters long. It is not a program and cannot run code or infect your device. It is data, stored in a plain text file, that the website created and that only the website can read.
Key Takeaways
- Cookies are small text files that websites store on your device so they can remember information about you when you return.
- First-party cookies come from the website you are visiting; third-party cookies come from other companies and track you across multiple sites.
- You can see what cookies are stored on your device and delete them through your browser settings, usually under Privacy or History.
- Blocking all cookies will break some websites, but you can usually allow cookies from the site you are visiting while blocking third-party trackers.
- Cookies expire on a date set by the website — some last a few hours, some last years, and some last only until you close your browser.
First-party cookies versus third-party cookies
A first-party cookie comes from the website you are actually visiting. When you log into your bank, the bank sets a cookie on your device that says "this person is logged in." When you add something to a shopping cart, the store sets a cookie that lists what is in your cart. These cookies are useful to you because they make the website work the way you expect.
A third-party cookie comes from a different company than the one running the website you are on. An advertising company might place a cookie on your device while you are reading a news site, then place another cookie on your device while you are on a different news site. Because the same company owns both cookies, it can see that you visited both sites and build a profile of your interests. This is how you see an ad for shoes on one website, then see the same shoe ad follow you to a completely different website.
Most browsers now block third-party cookies by default, though the rules vary. Apple's Safari blocks them automatically. Google Chrome is phasing them out but still allows them in many cases. Firefox blocks them by default but lets you turn that off. The reason browsers are moving this direction is that third-party cookies track you across the internet in ways you did not consent to and may not even know about.
How long cookies stay on your device
A cookie has an expiration date set by the website that created it. Some cookies expire after a few hours. Some expire after 30 days. Some expire after a year or more. A few are set to expire so far in the future that they might as well be permanent.
There is also a category called session cookies that expire the moment you close your browser. A session cookie might keep you logged into your email while you are using it, then delete itself when you shut down. This is useful for security — if you use a shared computer, the next person who opens the browser will not be logged in as you.
When a cookie expires, your browser automatically deletes it. You do not have to do anything. But you can also manually delete cookies at any time through your browser settings, which we explain in the next section.
Where to find and delete cookies on your device
Every major browser lets you see what cookies are stored and delete them. The exact steps vary slightly, but the idea is the same everywhere.
On Chrome, click the three vertical dots in the top right corner, then go to Settings. Click Privacy and Security on the left, then Cookies and Other Site Data. You will see a list of websites and how many cookies each one has stored. You can delete all of them at once, or click on a specific website to delete only its cookies.
On Firefox, click the three horizontal lines in the top right corner, then Settings. Click Privacy and Security on the left. Under Cookies and Site Data, you will see a button that says Manage Data. This shows you every website that has stored cookies on your device. You can delete all of them or select specific ones.
On Safari (Mac or iPhone), the process is different. On a Mac, click Safari in the menu bar, then Preferences, then Privacy. Click Manage Website Data to see all stored cookies. On an iPhone, go to Settings, then Safari, then scroll down and tap Clear History and Website Data.
On Edge, click the three dots in the top right, then Settings. Click Privacy, Search, and Services on the left. Under Clear Browsing Data, click Choose What to Clear. Make sure Cookies and Saved Website Data is checked, then click Clear Now.
What happens if you block all cookies
If you set your browser to block all cookies, many websites will stop working properly. You will not be able to stay logged in. Shopping carts will empty. Websites will not remember your preferences. Some sites will not load at all because they depend on cookies to function.
A better approach is to allow first-party cookies — cookies from the website you are visiting — while blocking third-party cookies. This way, the sites you use will work normally, but advertisers and trackers will have a much harder time following you across the internet. Most browsers let you set this up in Privacy settings without touching anything else.
You can also get more granular. Some browsers let you block cookies from specific websites while allowing them from others. If a particular site is not working, you can add it to an allow list. This gives you control without breaking everything.
Why websites ask for permission to use cookies
You have probably seen a banner at the bottom or top of a website asking whether you accept cookies. This is not because the website is being polite — it is because the law requires it in many places. The European Union's General Data Protection Regulation (GDPR) and similar laws in other countries require websites to tell you that they use cookies and get your permission before storing them.
In practice, most websites make it straightforward to accept all cookies and hard to refuse them. The Accept button is usually large and obvious, while the Reject button is small or hidden behind another click. This is legal but annoying, and it is why many people just click Accept without thinking about it.
The cookie banner itself is not a cookie — it is just a message. But the website will usually set a cookie that remembers that you clicked Accept, so it does not show you the banner every time you visit.
Cookies versus other tracking methods
Cookies are one way websites track you, but they are not the only way. Websites can also use pixels — tiny invisible images that report back to a server when you view them. They can use local storage, which works like cookies but stores more data and is harder to delete. They can use your IP address, your device fingerprint, or login information to identify you.
Cookies are actually one of the more transparent tracking methods because they are visible and you can delete them. Other methods are often invisible and harder to control. This is why privacy advocates sometimes say that cookies, while not perfect, are at least honest about what they are doing.
Frequently Asked Questions
Can cookies give me a virus or hack my computer?
No. A cookie is just text — it cannot run programs or execute code. It cannot install malware or access files on your device. The worst a cookie can do is store information about you that you did not want stored. If you are worried about security, deleting cookies is not the solution — using strong passwords, keeping your software updated, and not clicking suspicious links are much more important.
Why do I see ads for things I just looked at?
Third-party cookies and pixels let advertisers track what you view across many websites. When you look at a product on one site, an advertising company records that in a cookie. Later, when you visit a different site, that same advertising company sees the cookie and shows you an ad for the product you looked at. Blocking third-party cookies in your browser settings will reduce this, though it will not stop it completely.
If I delete my cookies, will websites still work?
Most websites will still work, but you will lose some convenience. You will have to log in again. Shopping carts will empty. Websites will not remember your preferences. The next time you visit, the site will treat you like a new visitor. Some sites that depend heavily on cookies might not load at all, but this is rare. You can always delete cookies from specific sites while keeping others.
Do I need to delete cookies regularly?
Not unless you want to. Cookies take up very little space on your device. The main reason to delete them is privacy — if you do not want websites to remember you, or if you do not want third-party trackers building a profile of your interests. Deleting cookies will not speed up your computer or fix performance problems.
What is the difference between cookies and cache?
Cookies are data that websites ask your browser to store so they can remember information about you. Cache is data that your browser stores automatically to make websites load faster — images, scripts, and other files that do not change often. You can delete both, but they serve different purposes. Clearing cache might make websites load slightly slower the first time you visit, while clearing cookies will log you out and reset your preferences.