Anyone who has ever used a computer has probably interacted with Google, which means the search giant has data about you. The question is, what exactly does Google know? The answer to this can be a bit complex because it really depends on which Google services you use. I, for instance, use Google search, Google Chrome, Google Drive, Google Maps, Gmail, Snapseed, Youtube, and Mailbox. In exchange for using these services, I, and everyone else must agree to share information about my online activities. Google then uses this information to better target its advertising services.
So what does Google know about you? Well you can find out but it takes a bit of sleuthing. First you need to sign in to your Google account and visit your web and app activity page. You can find this at https://history.google.com/history. Your web and app history page tells you what Google thinks it knows about you.
On this page you can find all the web pages you have visited. You can also delete pages if there is something you do not want Google to know. However, there are years of data saved and deleting it will not stop Google from advertising to you, it just means they are more likely to present untargeted advertising.
The next step in finding what Google knows about you is to click the menu button in the upper left of the screen. From here you can navigate to the Youtube, voice, location and device information Google keeps on you. Youtube has your viewing history, Voice has calling data, Location has your travel history for where you went using Google maps and device information has… well it has device information on the devices you use.
You can delete this information as well, but just like above, it will not stop Google advertising. However, before you start clawing the delete key, you might want to download the information Google has collected from your account settings page.
It may take a few days for Google to compile the information but you will most likely get a huge file with vast amounts of information about you. If you have ever owned an android phone, Google will have every photo you have ever taken. There will also be lots of location and search info. It is rather like getting a file compiled by a private investigator that has been following you for years.
While this level of data might seem a little frightening to some people, it is important to remember that you can adjust your settings to control the information Google can see. It is also good to understand that Google is not always great at understanding what you like. Most people search for all sorts of things and this can actually confuse the search giant. For instance, I bought a set of kitchen knives over a year ago for a friend. I am still seeing Google advertising for kitchen knives to this day. Keep that in mind before you worry too much about Google and what they know.