When you visit a website that uses cookies, a cookie will be downloaded to your computer or mobile device.    Most websites use cookies in order to improve your website experience and make your interaction faster and easier.  Cookies store your preferences and enables the website to 'remember' you, either for the duration of your time spent on the website (session cookie) or for repeat visits (persistent cookie).

Cookies do lots of different jobs.  Examples include:

  • A websites will 'know' if you have visited before and some websites will use this information to tailor what you see on the web page.  For example, a website may use a cookie to store your preferences such as page layout and colour scheme preference.
  • Some cookies will be used to identify if you are logged in to the website.  If a website doesn't use such a cookie, it will think you are a new visitor every time you move to a new page on the website.  For example, when you enter your login details and move to another page it won't recognise you and won't be able to keep you logged in.  Each page you visit will ask you to to enter your login details. 

So what is a cookie and how do they work?

A cookie is a very small text file which is placed on your computer or mobile device by a web server (the computer that operates the website you've visited).  A cookie contains some anonymous information such as a unique identifier, the website web address and some digits and numbers (which will only make sense to the website/server that placed the cookie).

If a website uses a cookie, every time you visit that website, the website server will read the cookie on your computer/mobile device and act accordingly.

Are cookies good for me and my website experience?

Can you imagine how frustrating it would be if you had to log in every time you visited a new web page having just logged in on the previous page?  Or the difficulty in adding items to your shopping cart?

The possibilities of cookies are endless, and generally the role of cookies is beneficial to your website experience.  They make your interaction with websites smoother - for no extra effort on your part.

Some cookies are very sophisticated.  They might record how long you spend on each page on a website, what links you have clicked, your preference to page layouts and colour schemes.  And for online shops, cookies are often used to store data on what items are in your 'shopping cart'.

Analytical cookies are used to measure how people interact with a website, what kind of browser or device they're using, how long spent on a website, etc.  This can help Webmasters improve the way a website works thus ensuring you can find the information you're looking for easily.

Can cookies be bad?

It depends on how you feel about businesses storing information about your browsing habits on your computer/mobile device.  There is nothing especially secret or exceptional about the information gathered by cookies, but you may dislike the idea of your browsing habits being used to display marketing advertisement (for example, when logged in to Facebook or Google), or your information being used to target you with special offers and promotions.  For example, if you you're browsing online for a car loan, you may see more advertisements for car loans - simply because the cookie has detected what you're looking for.

Cookie data is anonymous.  They do not contain personal information (i.e. name, address, sex, age, etc.) and you cannot be uniquely identified by a cookie.


You cannot catch a virus from a cookie, so don't worry.  Cookies are a simple text file and they don't have the ability to install a virus on your computer/mobile device.  For a virus to install on your system you must click a rogue hyperlink on a dodgy website or email or run a programme for the virus to install.

Steal information

A cookie cannot be used to steal information from your hard drive.  As previously mentioned, cookies are simple text files and they cannot be run as a programme.

Delete hard drive

A cookie cannot delete or corrupt your hard drive. 

Can another website read other cookies?

No, only the server which set the cookie will be able to retrieve or read the contents of the cookie it placed on your computer/mobile device.  As previously mentioned, a cookie contains the web address of the website as well as the path to the programme that created it.  The web address and path have to match exactly as they were set in the cookie for the server to read the cookie content.  There is no way for a different website or server to read the content of the cookie from another site.

How long do cookies stay around for?

Session cookies are placed on your computer/mobile device for the time you spend on the website and will clear when you close your browser.  

Persistent cookies remain on you computer/mobile device for a longer period until they are set to expire or the browser function to clear cookies is used.