Information about your device

When you browse the web, websites can collect information about your browser and your device. This information is either sent by your browser when you request a page or by the scripts executed by your browser on the page you visit.

Information about your device and your browser is used in a wide range of situations:

• The list of languages supported by your browser helps websites to show you a page in a language you can read when the page is available in multiple languages.
• Your operating system (Windows, Mac, iOS) and its version are useful when you want to download software. The website can send you the right software depending on your operating system (an application if you are on a smartphone or a Windows app if you use recent versions of Windows)
• The screen resolution can be used by websites to adapt the layout of a web page to make it more readable.

However, the most 2 common use cases of information related to your device and your browser are analytics and bot detection.

Analytics

Analytics scripts are everywhere on the web. The most popular, Google analytics, is present on around 50% of the 100,000 most popular websites. Analytics scripts help websites to understand the behavior of their users. For example, websites can analyze how long users spend time on a given page, how they interact with a page (mouse movements, scroll) and how these factors are impacted by the kind of device (smartphone, computer) or the browser (Chrome, Safari, Firefox).

Bot detection

Most websites aim to be used by human users. However, several studies show that almost half of the web traffic is not human: it comes from bots. Bots are computer programs that aim to automate tasks on the web. These tasks are diverse, ranging from indexing web content to make it easily searchable (what Google does), to malicious tasks, such as stealing accounts or conducting ad fraud.

To fight against bad bots, i.e. the bots that conduct malicious activities such as stealing accounts, websites leverage information from the user browser and device. They collect hundreds of attributes related to the device (GPU, number of CPU cores), the browser (its version, the list of plugins), the user behavior (mouse movements, typing speed), as well as information about the IP address (its location, the ISP) to distinguish between legitimate human users or computer programs mimicking humans.