big data

In the past, it was easy for people to keep track of their personal information. Like their possessions, people's information existed mostly in physical form: on paper, kept in a folder, locked in a cupboard or an office. Today, our personal information can be collected and stored online, and it's accessible to more people than ever before. Many of us share our physical location, our travel plans, our political opinions, our shopping interests and our family photos online – as key services like ordering a takeaway meal, booking a plane, taking part in a poll or buying new clothes now take place online and require us to give out our data.

Every search you make, service you use, message you send and item you buy is part of your 'digital footprint'. Companies and online platforms use this 'footprint' to track exactly what we are doing, from what links we click on to how much time we spend on a website. Based on your online activity, they can guess what you are interested in and what things you might want to buy. Knowing so much about you gives online platforms and companies a lot of power and a lot of money. By selling your data or providing targeted content, companies can turn your online activity into profit. This is the foundation of the growing industry of digital marketing.