"Want to freak yourself out?"

That was the beginning of a viral Twitter thread by Waterford, Ireland-based data consultant and web developer Dylan Curran explaining, step by step, how anyone can check what information Google has on them — from where they've travelled to their political views and even which stickers they've used online.

It's no secret that Facebook and Google collect data from people who use their services. But Curran was shocked by just how much he found about himself on Google.

He talks with Day 6 host Brent Bambury about why companies like Google store so much personal data, and what it could mean for the future.

Brent Bambury: What prompted you to look into how much data Google has collected about you?

Dylan Curran: I was on Twitter one Saturday, a little bit hungover — I have a life — and this person had essentially posted a thread, which was very similar to mine, but all they were going through was the Facebook data rather than the Google data as well. They showed that Facebook was storing your phone text messages or phone call records, and these collections are external to Facebook so they were storing things that they didn't need to store. And then after seeing that, and seeing the shock that so many people were experiencing, I decided to go in and do a little bit of investigation myself and compile it into something that people could easily read.

Want to freak yourself out? I'm gonna show just how much of your information the likes of Facebook and Google store about you without you even realising it —@iamdylancurran

So what other types of information were you able to find out had been collected about you online?

Oh God, so much. Number one was that they were storing Google incognito history. So if you were using private browsing, where they don't track your data, they did actually store it. So, say your wife wouldn't be able to see what you are doing in Google incognito, but Google will. And number two, they were mapping out your location every time you turned on your phone. So if your location setting is turned on, Google will log your location every time you turn on your phone. They store that and then they'll basically put it into a big database and you can go onto maps.google.com/timeline and see where you've been for the last four or five years.

2. This is every place I have been in the last twelve months in Ireland, going in so far as the time of day I was in the location and how long it took me to get to that location from my previous one <a href="https://t.co/I1kB1vwntT">pic.twitter.com/I1kB1vwntT</a> —@iamdylancurran

At the end of six hours how many gigs of information did you have that Google had on you?

Facebook has 600 megabytes and Google had 5.5 gigabytes — which, for context, is about three million more documents.

Now, if Google is storing that amount of data for every person who uses a Google product or a Google app, that's a lot of raw data. How is it all stored?

I did an estimation where around 2.2 billion people — 70 per cent of the internet— use Google, and this is conjecture, but I would say [they are storing] on average maybe one gigabyte per person. So if they have 2.2 billion gigabytes, that's 2.2 exabytes. That's three per cent of the world's online storage.

Just try and keep in mind that everything you do online does leave a footprint and it will be kept forever. - Dylan Curran, data consultant and web developer

How much does it cost to store three per cent of the world's online information?

Because of economies of scale, it's quite easy for them to store. Google makes on average $12 per person for their information, and the cost of storing it, I would say, is less than a fraction of a cent.

You said that Google's making $12 per person through our data. How did they monetize it into a profit?

What they essentially do is they take your information and then they build an advertising profile based on you. Advertisers pay to use that advertising profile to target you with the products and services that they want to sell you.

11. This includes every message you've ever sent or been sent, every file you've ever sent or been sent, all the contacts in your phone, and all the audio messages you've ever sent or been sent <a href="https://t.co/H8ng7bcyod">pic.twitter.com/H8ng7bcyod</a> —@iamdylancurran

People were shocked by the amount of information that you uncovered that Google had on you. What are the implications of all of this, of these private companies having so much data about so many people?

My problem really is that we don't know the implications. So I have no doubt that Google, Facebook, Snapchat, Instagram and Twitter, etc., aren't doing anything too nefarious with the data. I don't think that's what's happening. It's just that they are cataloguing all of this information. So if Google has information on a third of the population on the planet, down to everything they've done for the last 10 years, that does have a lot of negative connotations for the future. Especially in an ever-changing world. I do strongly believe that it's safer just to not have that kind of potential bomb available. I think it can be a little less extensive.

13. Somewhat pointlessly, they also store all the stickers you've ever sent on Facebook (I have no idea why they do this, it's just a joke at this stage) <a href="https://t.co/4F5sExbynf">pic.twitter.com/4F5sExbynf</a> —@iamdylancurran

But there doesn't seem to be a clear way of opting out. I mean, even if people change their privacy settings, is there any way of escaping having your data collected by Facebook or Google?

No, that's the thing. These are free services, and I don't have any problem morally or ethically with them collecting information in return for using the service. They're companies and they're trying to make money. What the issue is, really, is that they're just collecting too much. They're going too far.

What people can do is just be a little bit careful online. I'm not suggesting to delete Facebook or delete Google or anything like that. Just try and keep in mind that everything you do online does leave a footprint and it will be kept forever.

This interview has been edited for length and clarity. To hear more from Dylan Curran, download our podcast or click the Listen button at the top of this page.