You've probably heard of website cookies – most websites will prompt you to accept them once you land on one of their pages – but what exactly are they? Find out more about how website cookies can make your Internet experience faster and more convenient below.

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What are website cookies?

Website cookies are text files containing small amounts of data that are created when you arrive on a web page and are stored in your Internet browser automatically. Cookies are used to tailor the experience of using a specific website to a certain user. This information is encrypted, so only the website and your web browser can access it.

When you land on a web page, the law requires websites that use cookies to ask your permission to collect them. These are usually written when a new web page is opened after you've submitted information. They allow the website to 'remember' what information you've entered on a previous page – most websites require the use of cookies, as many basic functions won't work if you decide not to accept them.

Cookies can track which pages you visited while on a site, the IP address and general location of your device, and sometimes login information. This is why some websites will reference where you live, remember your login details from your previous visit, or may suggest returning to a page you've viewed in the past.

There are two main types of Internet cookie:

Session cookie

Session (or 'transient') cookies are only stored for the duration of a web browsing session and are deleted once it's over. These are stored in your browser's temporary memory folder and do not collect personal data.

Session cookies are commonly used by e-commerce websites to pass information from one page to another. For example, session cookies are the reason that the items you place into a shopping bag are retained until you hit checkout – and why they often disappear if you end the session and return later. If you only want to accept session cookies, this can be changed in your browser settings.

Stored cookie

A stored or 'persistent' cookie is kept on your hard drive until it expires (this expiration date is set when the cookie is created). Stored cookies collect important information about your activity on a website that makes future visits easier. For example, if accepted, stored cookies can remember your username and password so these details are automatically filled in when you return to a website.

Why are cookies useful?

Session cookies are vital to many basic website functions we're now used to, such as online shopping baskets. They act as short-term memory for a website, reminding the site what actions a user has performed on a previous page. Without session cookies, websites would treat every page you access while on a website as a brand-new visitor, causing issues that would impact everything from online shopping to social media.

Stored cookies can make your Internet browsing experience faster and more personalised by remembering personal data you have previously submitted. This means that some websites can tailor your experience based on your previous behaviour, such as offering you the chance to browse products you've already viewed.

Without the use of cookies, website servers would struggle to capture and retain the useful information website cookies gather, which would have an impact on speed and website performance.

What are third-party cookies?

A third-party cookie is a stored cookie that is created by a domain other than the website a user is visiting. Third-party cookies are typically used for advertising purposes, making a note of the pages, domains, or products a user has viewed to influence advertising.

This is the reason some products or pages seem to 'follow' you around. You may see them cropping up on your social media feeds or as banners promoting products, pages, or websites you've previously looked at.

Third-party cookies can be disabled in your browser's settings, preventing third party advertisers accessing things like your search history and browsing habits in order to serve personalised advertisements to you.

What is a cookie policy?

It's likely that you have encountered a cookie policy before – you'll often be prompted by a pop-up window to agree or disagree with a cookie policy upon your first visit to a website – but what exactly are they?

All websites that use cookies must disclose a cookie policy due to a piece of EU legislation that came into force in 2011 to help users better protect their online data. It's illegal for websites to not create or disclose a cookie policy. The law applies to any website that is used by people in the EU, so even if a website is hosted outside of the EU (in the US, for example), if it could potentially serve customers in the EU, it must adhere to cookie legislation.

How to clear cookies

There are plenty of reasons you may want to clear your browser's cookies – perhaps you've been shopping for a birthday present for your partner on a shared computer and don't want advertisements to give the game away, for example. Clearing your cookies will remove all the stored cookies currently sat in your browser, which could mean you'll have to resubmit some login details when revisiting sites, and features like "recently visited" products may be reset.

Clearing your cookies on Chrome

  • Click on the drop-down menu from the top right corner of your browser (indicated by three dots).
  • Select "History" from the dropdown menu, then click "Clear browsing history" from the options on the left-hand side.
  • Ensure that that the "Cookies and other site plug in data" box is selected, then click "Clear browsing history" to complete.

Clearing your cookies on Microsoft Edge

  • Open the drop-down menu in the right side of your browser, then select "Settings"
  • Halfway down the drop-down, you'll see a "Clear browser data" heading.
  • Click on the "Choose what to clear" button below, then ensure that the "Cookies and saved website data" box is ticked.
  • Click "Clear" to finish.

Clearing your cookies on Opera

  • To clear your cookies on Opera, select "Settings", then "Preferences" and "Advanced".
  • Here, click on "Cookies" and tick the "Delete new cookies when exiting Opera" box.
  • Once you've finished and closed Opera, your cookies will have been deleted.

Clearing your cookies on Firefox

  • First, click the burger menu and select "History", then select "Clear recent history".
  • Next, select the time range to "Everything".
  • Select "Clear now" to complete.

Clearing your cookies on Safari

  • Open "Preferences" from the Safari drop down menu, then click "Privacy".
  • To clear all cookies, click "Remove all website data", then confirm by selecting "Remove now".
  • It's also possible to clear cookies on a site by site basis by clicking "Details", then selecting the website information you'd like to erase.

Find out more on how cookies are used on plus.net and how to manage them read our guide.