What cookies are and why you might want to delete them

Cookies are small files that websites store on your computer to remember things about you — your login information, what you put in a shopping cart, or which articles you've read. Most cookies are harmless and make websites work better. But some cookies track your browsing across many different websites to build a profile of your interests, which advertisers then buy and use to target you with ads.

Deleting cookies removes that stored information. After you delete them, websites won't remember you the next time you visit, so you may need to log back in. But you'll also erase the tracking data that follows you around the internet. Firefox lets you delete all your cookies at once, or just the ones from specific websites.

Key Takeaways

  • Open Firefox, press Ctrl+Shift+Delete (or Cmd+Shift+Delete on Mac), and select "Cookies and Site Data" to delete all cookies at once.
  • You can also go to Settings > Privacy & Security > Cookies and Site Data and click "Manage Data" to delete cookies from individual websites.
  • If you want Firefox to delete cookies automatically every time you close the browser, turn on "Delete cookies and site data when Firefox is closed" in the same Privacy & Security menu.
  • Deleting cookies will log you out of most websites, so you'll need to sign back in the next time you visit.
  • Blocking third-party cookies in Firefox settings stops advertisers from tracking you across websites without deleting the cookies you already have.

Delete all cookies at once using the keyboard shortcut

The fastest way to clear all your cookies is to use Firefox's keyboard shortcut. Press Ctrl+Shift+Delete on Windows or Linux, or Cmd+Shift+Delete on Mac. A window titled "Clear Recent History" will open.

At the top, you'll see a dropdown menu that says "Time range to clear." Leave it set to "Everything" unless you only want to delete cookies from the last hour or day. Below that, make sure the checkbox next to "Cookies and Site Data" is checked. Uncheck anything else you don't want to delete — for example, if you want to keep your browsing history but only remove cookies, leave "Browsing & read History" unchecked. Then click the blue "Clear Now" button.

Firefox will delete the cookies when ready. You'll be logged out of most websites you were signed into, and the next time you visit those sites, they won't remember your preferences or activity.

Delete cookies from specific websites only

If you want to keep cookies from websites you trust but remove cookies from others, you can delete them one site at a time. Open Firefox and click the menu button (three horizontal lines) in the top right corner. Go to Settings, then click Privacy & Security in the left sidebar.

Scroll down to the section labeled "Cookies and Site Data." Click the button that says "Manage Data." A window will open showing all the websites that have stored cookies on your computer. Type the name of a website in the search box at the top — for example, type "facebook" to find Facebook's cookies. Click on the website name to select it, then click the "Remove Selected" button. Repeat for any other sites you want to remove.

This method is slower than clearing everything at once, but it lets you keep cookies from sites you use regularly while removing tracking cookies from sites you rarely visit.

Set Firefox to delete cookies automatically when you close the browser

You can tell Firefox to delete all cookies every time you close it, so you don't have to do it manually. Open Firefox, click the menu button, and go to Settings > Privacy & Security. Under "Cookies and Site Data," check the box next to "Delete cookies and site data when Firefox is closed."

Once you turn this on, Firefox will erase all cookies the moment you close the browser window. The next time you open Firefox, you'll be logged out of websites, and sites won't remember your preferences. This is the most private option, but it also means you'll have to log back in to your accounts every time you start Firefox.

If you want some websites to remember you even with this setting on, you can add them to an exception list. In the same "Cookies and Site Data" section, click "Manage Exceptions." Type the website address (for example, gmail.com) and click "Allow." Cookies from that site will be kept even when Firefox closes.

Block third-party cookies to stop cross-site tracking

Third-party cookies are placed by advertisers and data brokers, not by the website you're visiting. They follow you from site to site to track what you're interested in. Firefox blocks most third-party cookies by default, but you can make the blocking stricter.

Go to Settings > Privacy & Security and look for the section labeled "Enhanced Tracking Protection." You'll see three options: "Standard," "Strict," and "Custom." "Standard" is the default and blocks many trackers. "Strict" blocks even more, though it may break some websites. Click whichever level you prefer.

Blocking third-party cookies is different from deleting the cookies you already have — it stops new tracking cookies from being created, but doesn't remove old ones. For the most privacy, combine this setting with deleting your existing cookies using one of the methods above.

What happens after you delete cookies

After you delete cookies, websites will no longer recognize you. If you were logged into Gmail, Facebook, or your bank, you'll be logged out. The next time you visit those sites, you'll need to enter your username and password again. Websites also won't remember your language preference, font size, or other settings you customized.

Shopping sites won't remember items you added to your cart, and news sites won't remember which articles you've already read. This is the trade-off: you gain privacy, but you lose convenience. If you delete cookies regularly, you'll spend more time logging back in and resetting preferences.

Deleting cookies does not delete your browsing history, your saved passwords, or your bookmarks — only the small files websites stored on your computer. If you want to delete your browsing history too, use the same Ctrl+Shift+Delete shortcut and check "Browsing & read History" instead of (or in addition to) "Cookies and Site Data."

Frequently Asked Questions

Will deleting cookies delete my saved passwords?

No. Cookies and passwords are stored separately. Deleting cookies will not affect your saved passwords. If you want to delete passwords too, you can do that in Settings > Privacy & Security > Logins and Passwords, but it's a separate action.

Can I delete cookies from just one website without deleting all of them?

Yes. Use the "Manage Data" method described above: go to Settings > Privacy & Security > Cookies and Site Data > Manage Data, search for the website, and click "Remove Selected." This deletes only that site's cookies while keeping cookies from other websites.

If I delete cookies, will websites know I deleted them?

No. Websites cannot tell whether you deleted cookies or if they straightforward expired. Deleting cookies is invisible to the websites you visit. However, if you were logged in and suddenly aren't, a website might assume you logged out intentionally.

Does deleting cookies protect me from hackers?

Deleting cookies reduces tracking by advertisers, but it doesn't protect you from hackers. Hackers steal data through malware, phishing emails, or weak passwords — not through cookies. For security against hackers, use a strong unique password for each account and enable two-factor authentication when available.

What's the difference between deleting cookies and using private browsing mode?

Private browsing mode (Firefox calls it "Private Window") doesn't store cookies, history, or site data at all while you're browsing. When you close the private window, everything is erased. Deleting cookies removes data you've already accumulated. Private mode is more private for a single browsing session, but deleting cookies is useful if you want to clean up data from past browsing.