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 hundred bytes — that a website saves to your computer or phone. When you visit that website again, your browser sends the cookie back to it. The website reads what's in the cookie and uses it to remember something about you: what you had in your shopping cart, that you logged in, what language you prefer, or what ads you've seen.
Cookies are not programs. They cannot run code, install software, or damage your device. They are just data — like a note a store clerk writes down about you and hands back to you each time you walk in. The website reads the note, not the other way around.
Your browser stores cookies in a folder on your device. Different browsers keep them in different places, but you can view, delete, or block them through your browser's settings. Cookies expire on their own after a set time — anywhere from a few minutes to several years — unless the website or you delete them first.
Key Takeaways
- Cookies are text files websites store on your device to remember information about your visit or account.
- Your browser automatically sends cookies back to the website that created them, so the site can recognize you.
- Cookies cannot run programs or harm your device — they are just stored data that websites read.
- You can delete cookies, block new ones, or set your browser to clear them automatically when you close it.
- Some cookies track your activity across multiple websites for advertising purposes, while others only work on a single site.
First-party cookies versus third-party cookies
A first-party cookie is created by the website you are visiting. If you log into your email, the email site creates a cookie that tells it you are logged in. If 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.
A third-party cookie is created by a different company — usually an advertising network or analytics service — while you are on a website. For example, an ad company might place a cookie on your device while you are reading a news site. Later, when you visit a completely different website, that same ad company recognizes you through the cookie and shows you ads based on what you looked at before. This is how ads seem to follow you around the internet.
Most browsers now block third-party cookies by default, or let you turn off tracking across websites. First-party cookies still work because websites need them to function — you would have to log in every single time you refreshed the page without them.
Why websites use cookies
Websites use cookies for several practical reasons. A login cookie keeps you signed in so you do not have to enter your password on every page. A shopping cart cookie remembers what you picked so it is still there when you check out. A preference cookie remembers that you chose dark mode or English instead of Spanish.
Websites also use cookies to count how many people visit, which pages they look at, and how long they stay. This helps the website owner understand what is working and what is not. These analytics cookies do not identify you by name — they just track patterns of behavior.
Advertising networks use cookies to build a profile of your interests based on what you look at online. They then sell this information to advertisers or use it to show you targeted ads. This is why you might see ads for something you searched for on one site while you are on a completely different site.
How to see and delete cookies
In most browsers, you can view and delete cookies through the Settings menu. In Chrome, go to Settings, then Privacy and Security, then Cookies and other site data. You will see a list of websites that have stored cookies on your device. You can delete all cookies at once or delete cookies from specific websites.
In Firefox, go to Settings, then Privacy and Security, scroll down to Cookies and Site Data, and click Manage Data. In Safari on a Mac, go to Safari menu, then Settings, then Privacy, and click Manage Website Data. On an iPhone or iPad, go to Settings, then Safari, then Clear History and Website Data.
You can also set your browser to delete cookies automatically every time you close it. In Chrome, go to Settings, Privacy and Security, Cookies and other site data, and turn on Delete cookies and site data when you quit Chrome. This means you will have to log back in to websites each time you open your browser, but no cookies will be stored between sessions.
Blocking cookies and tracking
Most modern browsers let you block third-party cookies without affecting how websites work. In Chrome, go to Settings, Privacy and Security, Cookies and other site data, and select Block third-party cookies. In Firefox, go to Settings, Privacy and Security, Enhanced Tracking Protection, and select Strict. Safari blocks third-party cookies by default.
You can also block cookies from specific websites. In Chrome, visit a website, click the lock icon next to the web address, click Cookies, and toggle off the cookies you do not want. Some websites will not work properly if you block all cookies — you may not be able to log in or your shopping cart may not save — but most sites function fine with third-party cookies blocked.
Some people use browser extensions that block tracking cookies or hide your browsing activity. These tools work, but they can sometimes break website features. The simplest approach is to use your browser's built-in privacy settings, which are designed to block tracking while keeping websites functional.
The difference between cookies and other tracking methods
Cookies are not the only way websites track you. Pixels are tiny invisible images that websites embed in pages or emails to record when you view them. Local storage is similar to cookies but holds more data and does not expire automatically. Fingerprinting is a technique that identifies you based on your device settings, browser version, and other details — it does not require cookies at all.
Some of these methods are harder to block than cookies because they do not show up in your browser's cookie settings. However, blocking third-party cookies and enabling Enhanced Tracking Protection in your browser blocks most of these techniques as well. If you want stronger privacy, you can use a VPN, which hides your internet activity from websites and your internet provider.
Frequently Asked Questions
Are cookies dangerous or a security risk?
Cookies themselves are not dangerous — they are just text files. However, if a hacker steals a cookie that contains your login information, they could use it to access your account. This is why you should always use strong passwords, enable two-factor authentication on important accounts, and use HTTPS websites (look for the lock icon in your address bar).
Can cookies give me a virus or malware?
No. Cookies are data only — they cannot run programs or install software. A virus or malware comes from downloading an infected file or visiting a malicious website, not from a cookie. You can safely delete cookies without worrying about damaging your device.
Why do I still see ads for something I looked at weeks ago?
Advertising cookies can last for months or even years. An ad company might have stored a cookie on your device weeks ago when you looked at a product, and it is still using that cookie to show you related ads. Deleting your cookies will stop this, but new cookies will be created the next time you browse.
Do I need to delete cookies regularly?
You do not have to, but many people delete them monthly or quarterly for privacy. Deleting cookies will log you out of websites and remove your saved preferences, so you will have to log back in. If you want privacy without the inconvenience, block third-party cookies in your browser settings instead.
What happens if I block all cookies?
Many websites will not work properly. You will not be able to stay logged in, shopping carts will not save, and your preferences will not be remembered. Most people block only third-party cookies, which stops tracking ads while keeping websites functional.