In order for Google to identify you, you have to have a Google account. Without one Google may well have anonymous data about you as a cookie on on a phone or computer, but it is impossible to know what data that is (just as it is impossible for Google to know who you actually are). So all of the information below relies on you being logged in to your Google Account, which I'm sure you have. Ever logged in to an Android phone or tablet, used Gmail, or used YouTube as a registered user?
The email and password you use for those things (or Google Calendar, Docs, Drive etc) is your Google Account. You may - as I do - have several. In which case you will need to repeat all of what follows for each account. Amuse yourself by spotting the differences between each account.
First, let's check the Basics.
How well does Google know me?
Google used to be only a search engine. Remember that? Almost certainly you still use Google Search, a lot. And Google collects a lot of data about the searches you make, as it says a lot about you. Sign in and head over to Google and view the search history that Google holds about you. It's actually quite freaky to see what Google knows you searched for. You can also see your YouTube search history here.
More prosaic but also critical basic information can be found in your account details. Sign in and head to https://myaccount.google.com/ to see the basic data you gave to Google. Head to Dashboard and you can see records of an array of Google tools, and your activity with them. We'll click into a couple of these further along, but suffice to say that this is an important dashboard for finding out what Google knows about you.
This is the basic data Google is likely to hold about you:
Your name, gender and date of birth
Your email addresses
Your phone numbers
Where you live
Where you work
Website you've visited
Searches you made on Google Search
Your ad preferences (more below)
Places you've visited around the world
Your YouTube search history and recently watched videos
What you've said to the Google Assistant
How can I see my Google activity?
With ease, thanks to a relatively new tool that gives you a timeline of events and the ability to delete those events individually, should you want to.
Log into your account and head to the My Activity page. You'll see something like this:
This is what's called the Bundle view. You can drill down to the real details if you click Item view at the top left.
You can see more activity by clicking Other Google Activity from the left pane. This gives you links to many other Google services such as Sound searches, when you've left YouTube feedback or clicked on 'Not interested' on video suggestions, Google Play library information, Interests, News preferences, Call & Message information and even more.
How do I remove items?
Click the three vertical dots on any item in your activity to see a Delete option. However, bear in mind that only you can see this activity log: it isn't visible to others.
What does Google think you're interested in?
The principle reason Google tracks all this data about you is so that it can more successfully target you with advertising, in order to pay for the free services you access. Depending on your viewpoint (or demographic) this is either a sinister menace or a cool way of getting free stuff.
But it is interesting to find out just what Google thinks it knows about you, and how it uses that to target ads your way. Sign in and head to Settings. You will see what Google considers to be your gender and age, as well as your interests.
If you haven't told the truth when entering basic information - or you've never entered it - you might find it amusing that Google has your age or gender completely wrong.
When I do this test with my work email account Google thinks I am some sort of tech maniac. Which makes sense. But on my personal account my interests are naturally more broad. This matters because within this page you have the option to opt out of interest-based advertising.
These are adverts targeted at you because Google thinks you will be interested in their content. Personally I am happy to remain in - in part because I earn my living from advertising on this website, but mainly because it amuses me that all the adverts I see at work are for tech.
How to stop Google collecting your interests
You can opt out of interest-targeted ads by simply toggling off 'Ad personalization' using the button shown above.
You can also opt out of allowing website owners to track you via Google Analytics. Simply head over to the Google Analytics opt out page.
Where does Google think you've been?
One of the options available from the Google Settings Dashboard outlined above, is the ability to find out where Google thinks you have been. You can head there directly at Location History. This is typically tracked using the GPS in your phone: chances are even if you don't use an Android phone you'll still be signed into your Google account on an iPhone.
How to stop Google collecting location information
Click on Manage Location History at the bottom of the page and toggle off Location History.
What devices, apps and services have access to your Google data?
In many ways this is the most important test of all. One of the benefits of Android is that it lets you know what permissions are required by each app you install on Android.
But you encounter myriad Google apps and services on multiple devices. This page lists the devices and services, and what access they have. Click on a listed device and you can see further details and the opportunity to revoke, on the righthand side.
How can I change which Google information is visible to others?
With Google's About Me tool. This shows what's publicly visible, and you can click the pen icon to edit anything to remove it or change it.
It is well worth using Google's Privacy Checkup tool as well. Head to the Dashboard and click on the Get Started link. Now just go through the list and pick the options you're happy with.