What Is a Cookie on a Website? Everything You Need to Know

Last Updated: May 2026 · Written by DigiMetrics Hub Team · 6 min read · Category: Privacy & Web

Every website you visit sets cookies — and almost no one really understands what they are. This guide explains what website cookies actually do, the different types, the privacy implications, and how to manage them across every major browser.

What Are Website Cookies?

Cookies are small text files that websites store on your device through your browser. The name comes from 'magic cookies' — an old programming term for tokens of data passed between systems. A cookie typically holds a few hundred bytes of plain text: a session ID, a preference, an A/B test bucket.

Cookies are NOT programs. They cannot run code, install software, or directly infect your computer. They are simply small text records that the browser sends back to the website on each subsequent visit, allowing the site to recognize you and restore state.

How Do Website Cookies Work?

1. You visit a website for the first time
2. The server sends a small cookie file to your browser as part of the response
3. Your browser stores the cookie locally, tied to that website's domain
4. Next time you request anything from that domain, the browser attaches the cookie
5. The server reads the cookie and recognizes you (logged-in session, language, cart)
6. Your preferences and session state are restored automatically

Types of Website Cookies

• Session cookies — keep you logged in, deleted when the browser closes. Low risk.
• Persistent cookies — remember preferences across sessions, can last days or years. Medium.
• First-party cookies — set by the site you are visiting. Generally low risk.
• Third-party cookies — set by external advertisers and trackers. High privacy risk.
• Secure cookies — only transmitted over HTTPS. Lower risk.
• HttpOnly cookies — cannot be read by JavaScript, mitigating XSS theft. Lower risk.

What Information Do Cookies Store?

Cookies typically store login session tokens, shopping cart contents, language and region preferences, A/B test assignments, which ads you have already seen, and — in the case of third-party tracking cookies — fingerprints used to follow you across many different websites.

Are Cookies a Privacy Risk?

First-party cookies set by the site you are intentionally visiting are generally low risk and are usually necessary for the site to function. Third-party tracking cookies are a different story: they can quietly build a detailed profile of your behaviour across hundreds of sites and tie it to an advertising ID.

Most modern browsers now block third-party cookies by default, but trackers have moved to other techniques such as browser fingerprinting. Use our Browser Fingerprint tool to see how unique your browser actually is.

How to Manage and Delete Cookies

Chrome

Settings → Privacy and security → Clear browsing data → tick 'Cookies and other site data'.

Firefox

Settings → Privacy & Security → Cookies and Site Data → Clear Data.

Safari

Settings → Privacy → Manage Website Data → Remove or Remove All.

Edge

Settings → Privacy, search, and services → Clear browsing data → tick cookies.

Cookie Consent Laws You Should Know

In Europe, GDPR and the ePrivacy Directive require informed, opt-in consent for non-essential cookies. In California, CCPA gives residents the right to opt out of personal data being sold or shared. The UK's PECR mirrors GDPR in spirit. This is why almost every site now shows a cookie banner the first time you visit.

Frequently Asked Questions

Are website cookies dangerous?

Cookies themselves are not dangerous — they are plain text files and cannot execute code or install malware. However, third-party tracking cookies can be a privacy concern as they track your browsing behavior across multiple websites to build advertising profiles.

Should I accept all cookies?

For most websites, accepting only necessary cookies (session, preference) and rejecting third-party tracking cookies is the best approach. Many browsers now block third-party cookies by default.

What happens if I delete all cookies?

You will be logged out of all websites, lose saved preferences, and shopping carts will be emptied. Tracking data associated with your browser will also be cleared. You will remain anonymous to websites until new cookies are set.

Do cookies expire?

Session cookies expire when you close your browser. Persistent cookies have an expiry date set by the website, ranging from days to several years. You can always manually delete cookies before they expire.

Can websites work without cookies?

Basic websites can function without cookies, but many features rely on them. Login sessions, shopping carts, and personalization all typically require cookies to work. Without cookies, you would need to log in every single page you visit.