What's a cookie?
Browser cookies are little bits of information stored on your computer. They can be used to identify your computer and record the websites you visit, collecting data on who you are, what you like, and what you might be interested in – which is very valuable to advertisers.
A cookie is a piece of code passed between your browser and a website's server, when your browser connects to a website using the hypertext transfer protocol (HTTP) process. The cookie is stored on your computer the first time you visit the site, and it passes the identity of your computer from your browser to the website's server every time you revisit that site.
The good, the bad and the really nasty
Not all cookies are created equal. In itself, a cookie is just an application, but how they're set to work can determine if they have a positive purpose, or are being used to undermine the privacy and online security of the user.
- Short-term cookies or session cookies last for as long as someone is logged into a site. These are the kind used for banking transactions, and can store details for making payments, items in an online shopping basket and viewing balances. When a user logs out of the site, the session is finished and the information is no longer held by the website.
- Long-term or persistent cookies last longer than a single browsing session. They have many uses and can make returning to websites a better experience because they retain a user's settings. A persistent cookie, for example, can retain a language preference for a website or recognise that you've already registered, and will automatically prompt you to log in when you get to the website.
- Tracking cookies are persistent cookies that have a long timeline, and can be used to keep track of where else a user goes on the internet. Privacy advocates have raised concerns about the information that can be gathered about internet-browsing habits, because these kinds of cookies belong to third-party companies like advertisers, and they collect data on what sites you visit beyond the original website.
How do cookies work?
Cookies recognise if a user is new to the site, or is registered and has recorded preferences for certain content or settings.
A news site, for example:
- uses short-term cookies on its site to verify you when you log on
- may also have third-party cookies from marketers and advertisers that will also be installed on your computer when you visit the site.
Let's say you go from that news site to a technology review site. On the next site you visit after that you might see ads for online technology sellers, because the cookies have linked these sites together, targeting ads for online technology retailers at you in the hope that you're looking to buy a new gadget.
In this way, advertising companies build a picture of you and target advertising to you that has been closely aligned with your country, gender, interests and other attributes gleaned from your online habits.
How to control your cookie settings
Customise > Settings > Show advanced settings then under Privacy and Security > Content Settings > Cookies to adjust cookie settings.
Tools > Options > Privacy tab and check the 'Use tracking protection in Private Windows' and click 'Manage your Do Not Track settings.
Safari > Preferences > Privacy tab > Cookies and website data > choose Always block or Allow depending on your preferences.
Gear icon > Internet options > Privacy > Advanced
and then click Override automatic cookie handling to alter the settings. It's possible to allow first-party cookies so that cookies are allowed directly from a website but block third-party cookies that can be used for tracking.
How to delete your cookies
Customise > Settings > Show advanced settings then under Privacy and Security > Clear browsing data.
Tools > Options > Privacy tab and click Remove
individual cookies to see a list of all the cookies on your computer. Select one or all and delete.
Safari > Preferences > Privacy tab > Cookies and website data > Details > select one > remove, or Remove all > Done.
icon > Internet Options > Browsing History > Delete and check Cookies and website data box.