One thread ties it together
Three different companies hold three harmless-looking pieces of one person. On their own, each piece is thin. The trick is not one all-seeing eye — it is that the same identifier lets the pieces be matched to the same person, and combined into a profile sharp enough to guess what will move them.
This is a safe sandbox. The person below — Sam — is invented, and so is every figure shown. Nothing here reads your own accounts, nothing is stored, and a Reset button sits beside the controls throughout. If JavaScript is off, the explanation under the demo still describes exactly what the combination does.
How to read this page. The demo below is interactive, but the explanation carries the whole argument on its own — it reads fully with JavaScript off. Expand the "Deeper" box for what is and isn't shared, and where the law has stepped in.
What it holds about Sam
- Phone number
- Who Sam messages, and how often
- Times of day Sam is active
- Phone model + operating system
- The contacts in Sam's address book
🔒 Message content is end-to-end encrypted — not collected, and not needed.
What it holds about Sam
- Hashed phone / email
- Approximate location of Sam's phone
- Device identifiers
- Broker attributes (life stage, income band)
- A resolved, person-level ID
🔗 marks the same detail — a phone number or email — that turns up in all three cards. That shared detail is what lets the separate slices be joined into one.
All three hold the same detail — a phone number or email. Even when it is scrambled into a “hash” (a fixed jumble of characters), it is the same jumble everywhere, so it still works as the link:
+31 6 1234 5678 → 9f2a1c7b… (same every time) A hash is not anonymous. It hides what the detail says, but it is a stable label — the same person always gets the same hash — which is exactly what makes it a reliable key for joining the slices. Sam's profile inferred · fictional
Each company's slice on its own is thin. Press “Connect the data” to combine them.
What just happened
No company set out to build that profile. Each was optimising its own business: the messaging app wants to run a service, the social platform wants to sell attention, the auction wants to place a bid worth more than the next bidder's. The profile is what falls out when they share a key. That is the whole argument of this site: no conspiracy, only incentives.
The most important line is the locked one. The messaging app cannot read what Sam says — that part really is encrypted. It does not need to. Metadata — who, when, how often, on what device, from which contacts — is enough to place Sam in the combined picture. The encryption protects the content; it does not protect the pattern.
The key is the mechanism
Once a phone number or email is turned into a hash, it can be passed between companies without ever sharing the raw number — and still act as the same join key every time. A platform matches its own users to an advertiser's customer list this way; a data broker resolves a dozen scattered records to one person-level ID and feeds it into the ad auction. "Hashed" sounds like "anonymised." It is not: it is pseudonymous, which is precisely what makes it useful for joining records.
It builds up over time
The profile is not a single snapshot. Every message, visit and location is added to the same record, tied to the same key — and it does not expire. So something from weeks ago can still shape what reaches you now: that you were in contact with someone, that they follow a certain topic, that your phone was in a certain place. Gathered over time, that history is enough to predict what you will respond to next. You talk to a friend who has just moved house; days later the ads turn to sofas and paint — not because anyone heard you, but because the pattern around you now matches thousands of others who were moving.
This is why it can feel as though your phone is listening. When researchers examined more than 17,000 phone apps they found no secret microphone recording — and the machine does not need one. The record of who you contacted, when, and what is already known about them and you predicts the rest. In one well-documented case a retailer worked out that a customer was pregnant from her buying pattern alone, and began sending baby offers, before her family knew. No conversation was overheard; the accumulated pattern was enough.
What you can do
Make it harder to be profiled and tracked. None of these is a full fix — each one weakens the key that ties your slices together.
- Keep your accounts separate. In your Facebook, Instagram and WhatsApp settings you can stop them being linked to each other.
- Use a different email or phone number for different services. That removes the single key that joins your slices into one profile.
- Install a free tracker blocker such as uBlock Origin — it cuts how much the auction side can follow you around the web.
More, ordered by how much they actually change: What to Do →
Deeper — what is and isn't shared, and where the law has stepped in
Content vs metadata. WhatsApp messages and calls are protected by end-to-end encryption (the Signal protocol), so their content is not readable by the service. What flows to the wider company is metadata and account information — the distinction the demo's locked line makes.
Combining across services is the contested act. In the ad-tech industry this combining has its own names — identity stitching or identity resolution — but the plain idea is the same: link the pieces to one person. Germany's competition authority, the Bundeskartellamt, prohibited Meta in 2019 from combining a user's data across Facebook, Instagram, WhatsApp and third-party sites without genuine consent. The Court of Justice of the EU backed that approach in Meta v Bundeskartellamt (2023), and the case closed in 2024 only after Meta introduced an "Accounts Centre" letting EU users keep services separate. The "Apply EU rules" toggle reflects this: the architecture is the same everywhere, but in the EU the linking requires consent and can be switched off.
Transparency was found wanting (and is being litigated). Ireland's Data Protection Commission fined WhatsApp €225m in 2021 for not telling users clearly how their data was shared with other Meta companies. That penalty is not the end of the story — in February 2026 the EU Court of Justice ruled that WhatsApp may challenge the EU-level decision behind it, sending that case back to a lower EU court — so treat it as a live dispute, not a closed verdict.
Why this is a simulation. Sam is invented and every number is illustrative. We do not — and could not honestly — pull a visitor's own WhatsApp, social or broker data; the point is to show the mechanism, not to perform it on you.
Sources
- WhatsApp, Does WhatsApp collect or sell your data? — end-to-end encryption of content; metadata and account data sharing.
- Bundeskartellamt, Meta/Facebook — combining data from different sources (proceedings 2019; concluded 2024).
- Court of Justice of the EU (4 July 2023), Meta Platforms v Bundeskartellamt, Case C-252/21.
- Data Protection Commission (Ireland), Decision in WhatsApp transparency inquiry (2 Sept 2021; €225m). Under appeal, 2026.
- Meta for Developers, Advanced Matching — Meta Pixel — hashed email and phone as the match key for off-site activity.
- Cracked Labs / Wolfie Christl (2023), Pervasive identity surveillance for marketing purposes — resolving identifiers to a person-level ID and into real-time bidding.
- Irish Council for Civil Liberties, The scale of Real-Time Bidding data broadcasts in the U.S. and Europe — the profile is broadcast 376×/day (EU), 747×/day (US).
- Pan, E., Ren, J., Lindorfer, M., Wilson, C. & Choffnes, D. (2018), Panoptispy: Characterizing Audio and Video Exfiltration from Android Applications, Proceedings on Privacy Enhancing Technologies — a study of 17,260 apps found no evidence of secret microphone recording.
- Duhigg, C. (2012), How Companies Learn Your Secrets, The New York Times Magazine — Target's prediction of a customer's pregnancy from purchase patterns; predictive profiling over time.