Buzzfeed tracks a lot of sensitive personal information about users every time they visit the site. Reuters

Buzzfeed has built its reputation and success on figuring out exactly what people want to share online and it has done so brilliantly, with more than 130 million monthly unique visitors.

However what is less well known about the site whose headlines range from "27 Sexts That Are Better Than The Real Thing" to "26 Words That Have A Totally Different Meaning In Manchester" is the amount of data it collects about its visitors - especially those who take part in some of their hugely popular quizzes.

Web developer Dan Barker has written a blog post entitled Buzzfeed is Watching You about his investigation into the amount of data collected by the website every time you click on a link.

Initially Barker found that Buzzfeed was pretty much like every other website of its kind, sending data to Google Analytics which includes how many time you had visited; the date of your first visit; your location; whether you have connected Facebook with BuzzFeed; do you have email updates enabled; does Buzzfeed know your gender and age and how many times have you shared its content directly to Facebook, Twitter or email - and 25 other piece of information which Barker classifies as "mundane".

Barker notes that this data is attached to a "username" value which is the same across multiple browsers which he believes is recording his "user status, and an encoded version of my username" but could not say for certain if this username was personally identifying each user to an email address.

Sexuality, rape, mental health

Barker goes on to give an example of one of Buzzfeed's quizzes called How Privileged are You? which has been taken more than two million times.

The questions asked in the quiz ask you to reveal some very intimidate information about yourself, including questions about your race, eating disorders, rape, sexuality and mental health.

According to Barker, all of your choices are recorded meaning that anyone with access to Google Analytics could run a query along the following lines:

"Show me all the data for anyone who answered the Check Your Privilege quiz but did not check 'I have never taken medication for my mental health'."

The company's own privacy policy is relatively open about what it does with this data which is essentially to create more targeted advertising for users.

Responding to the blog post, Buzzfeed's Dao Nguyen who runs Growth and Data at the company, tried to reassure readers that while the data being collected is sensitive, it is not tied to any details that could identify you:

"We do not in fact record that it is 'you' browsing the site. The string sent to GA is not your username but an anonymised string that is not linked in any way to your account, email address or other personally identifiable information. Also, about 99% our readers are not even logged in."