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How does a browser cookie work?

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Quick answer

A browser cookie works as a small text file a website stores on your device to remember information between visits. It lets sites keep you logged in, save your preferences, and track items in a cart — by sending the saved data back each time you return.

Step by step

  1. A website saves a small text file in your browser.
  2. Your browser sends it back to that site on each visit.
  3. It remembers logins, settings, and shopping carts.
  4. 'Third-party' cookies can track you across different sites.
  5. You can view, block, or delete cookies in your browser.

People also ask

What does a browser cookie do?
It stores small bits of data so a website can remember you — keeping you logged in, saving preferences, or holding your cart between visits.
Are cookies dangerous?
Most are harmless and useful, but third-party tracking cookies can follow your activity across sites, a privacy concern you can block.
What's the difference between first- and third-party cookies?
First-party cookies are set by the site you're on; third-party ones come from other domains (often advertisers) and can track you across sites.

Part of the guide: How the Internet Works →