When Apps Watch You Without Wi-Fi
Apps track you offline using Bluetooth beacons, device IDs, and data brokers that merge online and offline behavior. Learn how this works, why it matters, and the steps you can take to minimize it.
Apps can track you offline through Bluetooth beacons, location metadata, and offline data brokers that match your device to real-world behaviors. You can reduce this tracking by adjusting device permissions and cutting off the identifiers companies rely on.
How do apps really track you when you’re not online?
Offline tracking blends physical sensors, wireless identifiers, and third-party data brokers. Retailers place Bluetooth beacons in stores, advertisers map device IDs to real-world locations, and data brokers merge everything into detailed profiles. A strong overview of how this ecosystem works is covered in the Electronic Frontier Foundation’s guide to device tracking: https://www.eff.org/wp/locational-privacy.
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What information do companies collect from you in the physical world?
Companies typically gather:
- Bluetooth and Wi-Fi probe requests
- Device advertising IDs
- Geolocation or motion sensor data
- Purchase history and loyalty card information
- Data from partner apps and third-party SDKs
To see how pervasive this ecosystem is, Mozilla’s Privacy Not Included project offers investigations into hidden tracking across everyday products: https://foundation.mozilla.org/en/privacynotincluded.
How can you tell if an app is using offline tracking technologies?
One practical method is to examine how an app uses your permissions. Follow these steps:
- Open your device’s privacy settings.
- Review each app’s access to Bluetooth, location, Wi-Fi, and motion sensors.
- Disable any permission that isn’t essential to the app’s core function.
- Check whether the app includes third-party advertising SDKs by reviewing its privacy policy.
- Monitor battery and Bluetooth activity for suspicious background use.
What are the main risks of offline app tracking?
Offline tracking enables companies to link what you do online and offline, creating highly detailed behavioral profiles. This can lead to targeted advertising in physical stores, discriminatory pricing, or data being shared with brokers you’ve never heard of. A New York Times interactive investigation into smartphone location tracking shows how billions of GPS points can be used to follow people’s movements in the real world: https://www.nytimes.com/interactive/2019/12/19/opinion/location-tracking-cell-phone.html.
What are the key facts I should know?
| Issue | Why It Matters |
|---|---|
| Bluetooth beacons | Track physical movement in stores and public spaces |
| Device IDs | Link your offline behavior to your online history |
| Data brokers | Sell combined profiles to advertisers or analytics firms |
| Permission creep | Apps ask for more access than needed |
How can I reduce offline tracking from apps?
- Turn off Bluetooth and Wi-Fi when not in use.
- Reset or limit your device advertising ID regularly.
- Use privacy-focused operating system features like Apple’s App Tracking Transparency or Android’s permission auto-reset.
- Use a firewall or tracker-blocking app to restrict background connections.
- Favor paid apps over ad-supported ones, which rely more heavily on data sharing.
FAQs
What is a Bluetooth beacon and why does it matter?
A beacon is a small radio transmitter used in stores; apps can listen for these signals to pinpoint your location indoors.
Can turning off location services stop offline tracking?
It helps, but it doesn’t eliminate tracking because Bluetooth and Wi-Fi signals can still reveal movement patterns.
Do data brokers buy offline data from apps?
Yes. Many brokers combine app-collected device identifiers with offline purchase and geolocation data.
Is offline tracking legal?
In most regions, yes, as long as notice is provided, though disclosure is often buried in privacy policies.
Does airplane mode block offline tracking?
It stops most network-based tracking, but stored sensor data can still be collected and uploaded later.
What to do next
Run a privacy permission audit on your phone using a trusted permission-manager tool to see which apps are tracking you the most.
*This article was written or edited with the assistance of AI tools and reviewed by a human editor before publication.
