ENDevice ID tracking links activity to an identifier that represents a device, a browser context or an app installation. Services use it to group events for analytics, advertising and security. What the identifier can track depends on where it comes from, who can access it and how long it remains available.
A phone can have several identifiers at once. An advertising SDK and an app analytics tool may use different values on that same phone. Neither value necessarily represents one person. A shared tablet may have several users, while one person may browse from several devices.
Types of Device Identifiers and Their Scope
A browser ID stored in a cookie and an identifier supplied to a mobile app can produce different records for the same phone. Before interpreting either record, check what the value represents and which software can access it.
| Identifier | Where It Comes From | What Its Scope Means |
|---|---|---|
| Android Advertising ID, Also Called AAID or GAID | Google Play Services | Available to Apps under Applicable Settings and Usage Rules. Users Can Reset or Delete It |
| IDFA | Apple Advertising Identifier API | On iOS 14.5 and Later, Access Requires Permission through App Tracking Transparency |
| Android ID | Android System | On Android 8 and Later, It Is Scoped to the Combination of App Signing Key, User and Device |
| App Instance ID | An App Analytics System | Represents an App Installation Within That System |
| Browser Client ID | An Analytics System, Often Stored in a Cookie | Recognizes a Browser Context While the Relevant Identifier Remains Available |
| IMEI or MAC Address | Cellular Hardware or a Network Interface | Serves a Different Purpose. Ordinary Webpages Cannot Directly Read These Values through Standard Browser APIs |
Android ID is separate from the Android Advertising ID. Resetting the advertising ID leaves Android ID unchanged. Apps signed with different keys can also receive different Android ID values on the same phone.
In Google Analytics 4, Device ID comes from the client ID on websites and the app instance ID in apps. Two browser profiles on one computer can therefore appear as separate users when a report relies on their different client IDs.
An IP address adds network context. Several devices can share one public address, and a single device can change addresses. It is therefore a weak basis for counting individual devices on its own.
How Does Device ID Tracking Work?
A typical analytics flow has three steps:
- An app obtains or creates an identifier suitable for its purpose.
- It sends that identifier with events such as an app launch, a product view or a purchase.
- The analytics service groups events carrying the same identifier.
Suppose an app uses ID X for one installation. A launch on Monday and a purchase on Tuesday both carry X. The service can connect those events and measure the time between them.
The purchase details live in the service database, with X attached to the record. The ID is a reference value. It carries no purchase history of its own and gives the app no access to activity in unrelated apps.
Connecting activity across devices requires another association. For example, a service may assign an account ID when someone signs in on a phone and a laptop. It can then associate both sets of events with that account where permitted. The device identifiers remain separate.
An installation that starts using a new ID may also appear new to the analytics service. If no other association connects the records, one returning person can be counted again. That can affect retention figures and audience estimates.
What Is Device ID Tracking Used For?
Teams use these records for three common tasks:
- App analytics: Group visits and feature use to measure whether installations return after their first session.
- Advertising measurement: Associate eligible ad interactions with later conversions under the relevant platform rules.
- Account security: Review repeated attempts or changes in activity associated with a familiar identifier.
Each purpose needs an appropriate identifier and access rules. An ID chosen for app analytics is not automatically suitable for advertising.
Security decisions need more than a matching value. Several accounts on one device may belong to a family or an authorized team. A changed identifier may follow a reset or a new app installation. It does not by itself establish device spoofing or account abuse.
Device ID Tracking vs Cookies, Fingerprinting and User IDs
A cookie can hold the identifier a website uses for analytics. Cookies and device ID tracking therefore overlap. One is a browser storage and request mechanism. The other is the use of an identifier to connect events.
A service can also assign an ID after matching a browser fingerprint. It compares observable features such as browser settings and rendering results. Recognition then depends on those features and the matching method, rather than on the continued availability of one saved cookie.
Account IDs connect records in a different way. Signing into the same account on a phone and laptop gives the service an explicit association between the two environments. If two people share that account, their activity may be combined in the report.
An analytics identifier also needs to stay separate from login credentials. Session management validates the state that keeps someone signed in. Recognizing a familiar analytics ID is not enough to authorize access to the account.
How to Limit Device ID Tracking
Start with the identifier you want to affect. Clearing browser data, changing mobile advertising settings and changing an IP address affect different parts of tracking.
Even without a name, a long event history can reveal interests and routines. Access to those records and their retention matter alongside whether the identifier can be reset.
Mobile App Controls
On Android devices with Google Play services, resetting an advertising ID replaces it with a new value. Deleting it removes the available identifier, and attempts to read it receive zeros.
On iPhone, users can manage app tracking permissions under Settings, Privacy & Security, Tracking. Apple's App Tracking Transparency rules cover access to IDFA and specified tracking across other companies' apps and websites. Denying permission does not stop every form of activity recording within an app.
App providers must respect advertising ID resets. Under Google's guidance, linking the new ID back to the old one through another identifier or fingerprint requires explicit user consent. A reset should not be silently undone by rebuilding the association.
Browser, Network and Account Controls
| Control | What It Affects | What It Does Not Automatically Do |
|---|---|---|
| Clear Relevant Cookies and Site Data | Identifiers Held in That Browser Data | Reset a Native App Advertising ID or Delete Server Records |
| Separate Browser Profiles | Cookies and Storage Shared between Supported Browser Contexts | Remove Associations Created by Signing into the Same Account |
| Use a VPN or Proxy | Network Routing and the Visible Exit IP | Remove Identifiers Stored by an App or Browser |
| Change Account Data Settings or Request Deletion | Data Retained by the Service, Within Its Supported Processes | Clear Every Identifier Held Elsewhere |
For browser work, cookie isolation helps keep stored identifiers separate between supported contexts. Signing into the same account in both contexts still gives that service a way to associate their activity.
Account history needs separate attention when reducing a digital footprint. For example, clearing a shopping site's cookies may remove its local analytics ID. Signing back in can restore access to the order history held by the site. The retained history is not evidence that cookie deletion failed.
FAQ
Is a device ID the same as an IMEI?
IMEI is a specific cellular equipment identifier. Device ID is a broader label whose meaning depends on the system. In an analytics report, it may represent a browser context or an app installation instead of cellular hardware.
Does clearing cookies stop device ID tracking?
It can remove a browser identifier stored in the deleted cookies. It does not automatically affect identifiers used by native apps. A service may also retain account associations or other state, so the result depends on its recognition method.
Does a VPN hide a device ID?
A VPN changes the network path and usually the public IP visible to a destination. An app or website can still receive an identifier included in its own requests. Changing the exit address does not remove that value.
What is the difference between resetting and deleting an advertising ID?
For Google's advertising ID, resetting provides a replacement value. Deleting removes the available ID without assigning a replacement. Neither action automatically erases historical events already held by a service. These controls should not be confused with resetting every identifier on the device.
Can a device ID track someone across devices?
One device identifier does not automatically follow a person to another phone or computer. A service needs an additional association, such as an account mapping, to connect the records. The accuracy depends on that association.
Can a device ID reveal a name or exact location?
The identifier itself does not contain those details. A service may hold separately collected data associated with it. Access to that data matters. Knowing an ID alone does not provide live location access or control of the device.
