Google's two buying platforms, Google Ads and DV360, hold two big advantages in programmatic:
Exclusive access to YouTube inventory
The ability to activate Google's own audience segments (affinity and in-market)
This piece is about the second one.
Google's audience segments are one of the most fascinating mysteries in programmatic. They are mysterious for three reasons:
The ingredients are secret.
So is where they come from.
The way the segments behave is strange, to say the least.
The mystery of Google's audience segments: what's actually inside?
Where Google collects user data
Google feeds its audience segments from two kinds of sources:
Its own ecosystem: Search, YouTube, Maps, Play Store and Discover
External data it picks up… from everyone else
We wanted to know more about that second source, so we ran a small study. We found two open-source tools that check what Google does inside apps:
Exodus Privacy runs from a computer. It scans an app's code for embedded Google tools, including AdMob, DoubleClick, Firebase and Analytics tags.
PCSA, short for the French name of App Tracking Protection, runs inside the DuckDuckGo Android app. It detects and blocks Google tracking tags as they try to fire from each app.
We went with the second, because it tracks activity in real time.
We downloaded many of the most-used apps in France. Then we checked whether they fire tags that could let Google collect information on their users.
The tool has technical limits:
It only works on Android.
It doesn't catch server-side tracking.
It misses tracking that fires in sections of an app we didn't browse.
Here is what our tests found:
PCSA detects and blocks user data sharing with Google | No sharing with Google detected | |
|---|---|---|
AUDIO | France Info CastBox Deezer Podcast Addict Spotify TuneIn Radio | |
BANKING | BoursoBank Caisse d'Epargne Qonto Macif | Crédit Mutuel |
La Poste Mail Orange Yahoo | ||
NEWS | 20 Minutes Le Figaro Le Monde Le Parisien Les Echos Ouest France ProgrammeTV SudOuest | |
FOOD | Deliveroo Uber Eats TheFork | |
RETAIL | Auchan Carrefour LeBonCoin Magasin U Temu Vinted | Amazon Action Leclerc Lidl Plus |
SPORTS | Foot Mercato L'Equipe | |
VIDEO | HBO M6+ myCanal | Arte FranceTV Netflix TF1+ |
TRAVEL | AirFrance Citymapper EasyJet Getaround Kayak Pages jaunes Ryanair Skyscanner SNCF Trainline Transavia TripAdvisor | Airbnb eDreams Flixbus |
OTHER | La chaîne météo Se Loger | Doctolib |
Google trackers are deployed at scale across the biggest apps. Many of these apps likely use Google tools that give Google access to the device's advertising ID.
A caveat. That doesn't necessarily mean all these apps feed Google's audience segments. But the technical bridge that would let Google do it does exist.
The takeaway: Google's segments are processed products, built from a huge collection footprint. Still, plenty of "organic" ingredients go into them.
🎶"Old McGoogle had a farm, Ee-i-ee-i-o. And on his farm he had some data, Ee-i-ee-i-o."🎶
What information flows back to Google
PCSA has a second useful feature. It shows which user signals Google generally collects.
According to the tool, there are a lot of them. Thirty-two, to be exact:
Type of information | Information Google generally collects in apps, according to PCSA |
|---|---|
Identity and identifiers | First name Last name Gender Email address Unique ID Android advertising ID Cookies |
Location | Local IP address GPS coordinates City Postal code Country State Time zone |
Device | Device name Phone brand Phone model System volume Screen definition CPU data Phone orientation Available internal storage Screen resolution Battery level Charging status Headphone status Device boot time Total device memory OS version OS build number Language |
App | App name App install date App version |
Telco | Network connection type Network carrier |
None of this means Google uses every one of these signals for advertising, so the magic formula stays secret. But it gives a sense of the ingredients Google could use.
The magic of Google segments: elasticity?
Google has a huge, high-quality footprint for collecting audiences. It also picks up a long list of signals on how users browse.
But something is odd about the Google segments available in DV360 and Google Ads. They are big. Very big. Really, really big.
We compared several DV360 Inventory Availability Reports to measure the size of Google's segments:
A first report filtered on France, the Google Ad Manager SSP and web/mobile web showed about 40.8 million available cookies.
A second, identical report added Google's segments as a dimension.
That gave us the share of the cookied population on Google's exchange that belongs to each Google segment.
Here are the results. Google has 37 top-level category audience segments, such as "In-Market Categories > Consumer Electronics." They average 35 million cookies each. By Google's count, each segment holds 88% of the cookied population on average. The figure reaches 94% for "Home & Garden" and "Financial Services," and 83% for "Business & Industrial Products."
That is strange. In theory, segments that target everyone make no sense, since every targeting option would then deliver the same performance.
Yet despite their gargantuan size, a "Travel interest" segment activated for a travel advertiser outperforms the other audiences in most cases.
It's as if Google had found the magic formula for combining insane reach with performance.
We have a theory that could explain it.
Each segment may actually be made up of several subgroups. Each subgroup has a different degree of affinity with a very high-quality seed audience.
That would let Google play on the elasticity of its segments:
Concentrate delivery on the highest-quality subsegments when daily pacing is low or the ROAS target is aggressive
Extend delivery to less closely matched subgroups when daily pacing is very high or the reach target is aggressive
That would give Google a huge advantage over every competitor on audiences.
The magic of Google segments: elasticity?
Why Google's segments are breaking the programmatic audience market
Open web ad spend keeps falling. It dropped 10% in 2025, according to French digital marketing trade body Alliance Digitale. In that market, publishers and advertisers will struggle to sell their first-party audiences to advertisers and media traders... if they also let Google tap those same audiences to enrich its own segments.
And Google's segments make a very tempting offer to advertisers and media traders:
A huge, "organic" collection footprint: every Google environment plus many external sources, including very high-quality providers.
Elasticity: the segments seem to adapt to traders' reach and performance needs through a modular design.
Buying mode: they can be activated in the open auction, media traders' preferred buying mode, which takes 80% of programmatic spend according to Alliance Digitale.
Cookieless: they deliver normally on browsers that block cookies. About 30% of impressions ran on Safari in our internal tests.
Available on Google inventory: they enrich targeting across Google's own ad ecosystem, starting with YouTube.
Interoperable: if Google can link user data captured in an app to the user's Google account, the segments can support cross-device and cross-environment targeting.
Price: last and best of all, they are free to activate. Media traders can potentially save 50% of the CPM on a standard display campaign.
How Google data devalues publishers' first-party segments
In 2026, publishers could strengthen the audience side of their offer in two ways.
On offense:
Publishers could make their own audiences work on Safari and in the open auction by pushing their audience segments into DSP data marketplaces. Traders would get easy access to the segments with strong reach, and alternative IDs would be easier to activate.
They could also adopt a login wall. Collecting users' email addresses makes their segments more interoperable and could even bridge them to CTV and audio. Some publishers have already made the move, such as French sports daily L'Équipe in its mobile app.
On defense: the choice of tech stack is becoming central in programmatic to protecting a company's assets, its audiences above all. Some programmatic players, broadcasters and retailers in particular, chose not to rely on Google's highly advanced tech stacks. That keeps their audiences from being siphoned off.
