No, Google Isn’t Eavesdropping on You for Those Crazy Ads and Predictions

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«My phone was in my pocket as I was talking to my friend about XYZ. I had never heard of XYZ before (my friend brought it up), and I didn’t google it or anything. Yet when I opened an app a day later, I saw ads related to XYZ! Is Google listening in on my conversations to serve me ads?»

You might have seen a variation of this subject popping up on Android or technology forums (it seems pretty popular on Reddit, where I see it every few months in /r/Android, /r/technology or a device-specific subreddit). Is it true, then? The short answer is no.

The longer answer is: Google doesn’t need to, because it gathers a lot more information about you and your surroundings to deliver targeted ads or tailored search suggestions. Want an even longer answer? Then keep reading!

Why Google Isn’t Constantly Listening

First of all, let’s start off by explaining why Google isn’t constantly listening to your conversations (regardless of privacy and ethical implications). The explanation is rather simple: it would require your phone to be constantly awake, and would use up all your battery in a matter of hours (even if you’re not using your phone).

«But OK Google detection does exactly that and barely affects the battery!», you might say. However, that’s a bit different. Before going into more details, a very quick reminder on how Android power management works:

Battery drain is maximal when the device is fully awake (that’s when you’re normally using your phone), noticeable but less-so when partially awake, and negligible when asleep. To give a rough idea, my Nexus 6P would use up around 25% of battery per hour if kept constantly in the first state, around 5% per hour in the second with normal CPU usage, and a negligible amount (around 0% per hour, theoretically) in the last state. If the CPU is actively being used while partially awake (as opposed to simply holding a CPU wakelock), then power usage can shoot up by quite a bit and drain the battery in a matter of hours. As you might have figured out by now, the CPU requires a lot of battery when it’s actively being used.

That brings us to voice recognition, which is a CPU intensive task. Doing it constantly would ensure your phone’s battery doesn’t last you a full day even if you don’t touch it. Doing it accurately is even more of a challenge, which is why Android (and other platforms, such as iOS) usually compress voice recordings and send it to the cloud for processing on more powerful computers.

How does “OK Google” detection work, then? It actually uses a special feature in your phone’s processor, designed to be extremely light on power as it doesn’t require the CPU to be fully awake. The feature is quite limited, though, and will only detect specific sound bites set by the OEM. This is a much simpler problem than voice recognition (listening to what the user is saying and understanding it to translate it into words). Instead, it only detects “hotwords” (checking if heard noise is similar to the noise saved by the OEM). Only once a hotword is detected, the phone is woken up and Google Assistant launched.

In summary: is Google constantly listening in? No. Can Google constantly listen in? Yes (but that would nuke your battery and/or data usage and would be noticed rather quickly). More importantly, though: does Google even need to listen in to every word you say to give you scarily-accurate advertisements or search suggestions?

How Google Shows You Advertisements

Developers reserve spots in their apps and lets Google know about them, Google handles the rest. It doesn’t just deliver random advertisements, though: it will do its best to deliver targeted advertisements that you’re most likely to be interested in. Several factors are taken into consideration, including:

The collected information isn’t device specific. If you use a computer and an Android device, all this data will be linked to your account. In some cases, Google may also link searches done on your network (e.g. by a family member connected to the same router) to you.

It’s clear that Google knows quite a lot about you, unless you’ve taken measures against that (if you are, make sure to visit the privacy and security hub Google launched a while back; you may also want to check out Pulser_G2’s “Say Sayonara” series). And even if you did, Google can still figure out quite a bit about you, even as an anonymous user.

With all this in mind, it’s not too difficult to see how Google can deliver accurate advertisements. Never googled a topic before, but started getting advertisements about it after having discussing it with a friend? There are several explanations for that:

You were getting advertisements about it before, but you’ve never noticed it till now.

You’re discussing a recent topic, which is why advertisements are popping up now.

Someone else googled the topic, but you were on the same network so Google thought it might be you.

How Google Shows You Search Suggestions

A variation of the tale we imagined at the beginning of this article involves seeing spooky search suggestions, not advertisements. While you might not be aware of it, search suggestions are actually different from user to user, and are based on several factors other than what you’ve typed so far:

If you’re signed in, searches you’ve done in the past: if you’re a programmer and often search for programming-related queries, you’re more likely to get results about the programming language than the island if you search for “Java”.

Trending stories (popular topics in your area right now). This includes searches other users around you are performing, allowing Google to give you suggestions about popular nearby events, for example.

New and diverse results are prioritized, so that you don’t get several results that are too similar or too old to be relevant.

Again, it’s easy to see how you might get suggestions that would seem impossible, but actually make a lot of sense if you know how it works. Visited some shop and heard a new song, then asked your friend its name and Google later suggested the full name after typing three letters? It’s probably just a popular new song, and other people around you are probably just googling it as well.

Can You Opt-Out?

If you’d rather opt-out of as much tracking and targeted data as possible, follow these steps — but keep in mind that a lot can be traced back to your online identity, even if anonymously:

Wrapping Up

To wrap-up, is it possible that Google is listening to your conversations? Absolutely (from a purely technological point of view)! In practice, however, it’s extremely unlikely for the following reasons:

The battery drain required to do so would be extremely noticeable. (Certainly more than the random Play Services fits.)

It would be easy to detect by monitoring network usage and sent packets, CPU usage/wakelocks or even microphone awake state logging. (We would have caught on by now.)

The alternative explanations listed in this article are very compelling, and people really underestimate how accurate predictions can be just from contextual data. (And it only gets creepier!)

In other words: is eavesdropping possible? Yes. It is needed? Not really, not for the targeted advertising or auto-completion that we’re seeing. Is it happening on your Android device, to net you better predictions? No.

Have you had “spooky” Google experiences? Share your story below!