Cookies and online tracking, explained

The helpful kind

First-party cookies come from the site you’re visiting. They remember that you’re logged in, your language, and what’s in your shopping cart. Without them, you’d have to sign in on every page.

The tracking kind

Third-party cookies come from other companies, often advertisers, whose code is built into many different websites. When the same ad company sees you on a recipe site, a shoe shop and a news site, it can guess what you’re interested in. That’s why the boots you looked at once follow you everywhere.

Those cookie pop-ups

Many sites ask you to accept cookies. Look for Reject all, Necessary only or Manage settings. Choosing them usually keeps the site working while turning off most advertising cookies.

It isn’t only cookies

Sites and apps can also recognize you when you sign in, through apps on your phone, and through details about your device. So blocking cookies cuts tracking down but doesn’t stop it entirely.

What it means for you

Cookies aren’t viruses and they can’t read your files. The trade-off is privacy: how much of your browsing advertisers can connect together. A few settings make a real difference.

Quick tips

• Choose “Reject all” or “Necessary only” on cookie pop-ups when you see it.
• Check your browser’s privacy settings. Some browsers, like Safari and Firefox, block many cross-site trackers by default; others let you turn it on.
• On iPhone, you can tell apps not to track you under Settings > Privacy & Security > Tracking.
• Private browsing clears cookies when you close the window, but it doesn’t hide you from websites or your internet provider.
• Clearing cookies signs you out of sites, so have your password manager ready.