Advertising ID vs. IP Address: How Mobile Tracking Uses Each

What Advertising IDs Mean in Simple Terms

An Advertising ID is a resettable identifier for your mobile device. It identifies your device to apps and advertisers so they can maintain preferences and attribute actions (such as downloading an application) to a specific campaign. Unlike a permanent serial number or an IMEI, users can manually reset or delete this identifier at any time.

On Apple devices, this is known as the IDFA (Identifier for Advertisers). On Android, it is the GAID (Google Advertising ID). These identifiers were developed as an alternative to permanent hardware identifiers, allowing the industry to measure performance without creating a permanent link to a specific physical device. Resetting the identifier makes long-term tracking more difficult by breaking the continuity of the profile.

However, an Advertising ID is only one factor in device identification. While it is an accurate method for an app to identify a persistent user, it is frequently combined with network signals to improve profile stability. Learn how more advanced fingerprinting techniques differ from simple IDs here.

TL;DR: Quick Summary

• Advertising ID: Device-level, used for app tracking, manually resettable by the user.
• IP Address: Network-level. Reflects the network connection currently in use. Changes with Wi-Fi or cellular switches.
• Persistence: Ad IDs remain stable across networks; IP addresses typically change between different access points.
• Privacy Control: Advertising IDs are managed in system settings; IP addresses can be masked with a VPN or Proxy.
• Use Case: Ad IDs help identify user sessions across apps; IPs provide network and geographic context.

What an IP Address Represents in Tracking

While the Advertising ID identifies the device profile, the IP address reflects the network connection currently in use. It serves as the routing address for data transmission. Because an IP address is tied to the network infrastructure, it reveals approximate physical location and the associated Internet Service Provider (ISP).

In mobile tracking, IP addresses are often considered transient signals. If a device moves from home Wi-Fi to a public hotspot or 5G cellular connection, the IP address typically changes. Furthermore, because many users on a mobile network share the same public IP via Carrier-Grade NAT (CGNAT), relying on IP alone for advertising is often less precise than using a device ID. See why CGNAT complicates mobile IP tracking here.

IDFA (iOS) vs. GAID (Android) vs. IP

While both major mobile ecosystems use Advertising IDs, their privacy frameworks have diverged. Apple's App Tracking Transparency (ATT) requires apps to request explicit permission before accessing the IDFA. If a user denies the request, the app is prohibited from accessing the identifier, forcing developers to rely on alternative, less precise attribution methods.

Google is developing the Privacy Sandbox, which aims to move toward interest-based targeting APIs that process data on the device rather than sharing a persistent identifier with external servers. Throughout these transitions, the IP address remains a primary fallback signal because it is a functional requirement for network communication. Check your own IP and see what ad networks can currently see about your location.

How Mobile Tracking Uses Each Identifier

Ad systems typically utilize both signals to answer different questions during the attribution process:

• The Click: When a user interacts with an ad, the system records the Advertising ID and the IP address.
• The Install: After the browser or app store processes the download, the app is opened. The ad network compares the ID and knows which click most likely led to the install. This is referred to as deterministic attribution.
• The Fallback: If the app generally no longer has access to the IDFA, the system attempts a high-probability match by correlating the IP address, device model, and timestamp of the install. This is referred to as probabilistic attribution.

Technical Deep Dive: How These Identifiers Are Built

An Advertising ID is a 128-bit UUID (Universally Unique Identifier). For example, an IDFA might be represented as AEBE52E7-03EE-455A-B3C4-E57283966239. This string is not hard-coded into the hardware; it is a software-defined value managed by the OS. It is stored in a secure system directory that apps can query only with active permission.

An IP Address is a fundamental part of the network layer. In IPv4, it is a 32-bit number. In IPv6, it is a 128-bit number. Use our CIDR guide to understand how these address blocks are organized here. Because the IP is necessary for the network handshake, it is more difficult to suppress than a voluntary software identifier.

How Ad Systems Combine Multiple Signals (Identity Stitching)

Ad tech platforms often use Identity Stitching to build comprehensive profiles. If a user interacts with a retailer's app and then later visits the same retailer's website via a mobile browser, the browser cannot access the Advertising ID. However, the server can see the IP address and the User Agent string.

By correlating the IP address and specific device metadata (such as OS version and screen resolution) between the app and the browser, a tracking provider can estimate with high confidence that the two sessions belong to the same user. This cross-platform linking helps explain how tracking can persist across different environments. This persistence is a key area of focus for modern privacy regulations.

The Role of First-Party Data vs. Third-Party Trackers

There is a significant distinction between first-party and third-party tracking. If a user is logged into a unified account system (such as Google or Meta) across multiple apps, the provider does not require an Advertising ID to identify the user; they use an internal Account ID. This is First-Party Data.

Advertising IDs were primarily intended for Third-Party Trackers—independent entities that aggregate data across many unrelated apps. These companies collect identifiers from various sources to build a cross-app profile. The primary goal of frameworks like Apple's ATT is to restrict third-party access to these persistent identifiers.

Attribution and Fraud Detection

IP addresses are commonly used in fraud detection. If an ad network receives thousands of conversion signals from the same Advertising ID, it often indicates automated activity. Conversely, if numerous installs appear with unique Ad IDs but originate from the same data center IP address, it may indicate a click farm. Learn more about how click farms rotate IPs to obscure these patterns here.

What Changes When You Reset an Advertising ID?

When a user resets the Advertising Identifier in their device settings, the old ID is replaced with a new identifier. For an ad network, the user may appear as a new device unless other identifiers are available to link the new ID to the previous profile.

If the user immediately logs into a persistent account after resetting the ID, the platform can link the new identifier to the existing account history. Resetting the ID is most effective when the user remains unauthenticated across different apps.

iCloud Private Relay and the Future of IP Privacy

The IP address has historically been a stable tracking signal. Apple's iCloud Private Relay attempts to mitigate this by routing traffic through two separate relays. The first relay knows the user's IP but not the destination; the second relay knows the destination but sees only a generic regional IP address.

This architecture is designed to limit the utility of IP-based tracking and fingerprinting within Safari. As these privacy-focused network architectures become more common, the ad tech industry is increasingly shifting toward Differential Privacy and Contextual Advertising, where ad delivery is based on current content rather than historical user behavior. Check if your connection is currently using a relay or VPN here.

Common Mistakes in Managing Your Identifiers

• Relying solely on tracking restrictions: Toggling a single privacy switch does not make a device invisible. Permissions for Location Services or Bluetooth can also serve as secondary identification signals.
• Resetting the ID on a static network: If a user resets their Ad ID while connected to a static home IP and immediately resumes activity in a tracking-heavy app, the system can use the IP address to re-associate the new ID with the old profile.
• Overlooking the User Agent: A device's User Agent (hardware model, OS version, and language settings) can be highly distinctive. If these traits remain unchanged, resetting the software ID may only offer temporary privacy.

Comparison Table: Mobile Identifiers

How Privacy Settings Affect Both

Identifiers are increasingly restricted by default. Frameworks like Apple's ATT allow users to refuse tracking, at which point the app no longer has access to the IDFA. This has led to an increase in probabilistic attribution, where networks attempt to identify users through IP addresses and other metadata.

Combining IP masking with tracking restrictions offers stronger privacy. For example, using iCloud Private Relay alongside ATT significantly reduces the data points available to third-party ad networks. Understanding these distinct layers is essential for maintaining control over your digital footprint. Run a full privacy audit on your current IP here.

Common Myths

• Myth: Incognito mode hides my IP address. No. Incognito mode only restricts local history and cookies. The ISP, destination servers, and ad trackers can still see the IP address.
• Myth: Deleting an app deletes the associated ad profile. No. The Advertising ID is held at the OS level. If the user installs a different app from the same developer, they may still be able to associate activity with the same device.
• Myth: A VPN makes a user anonymous to all apps. Only partially. While the IP is hidden, if the app has permission to access the Advertising ID or if the user is authenticated with an account, they are still potentially identifiable.

Conclusion

Advertising IDs and IP addresses serve distinct, complementary roles in the mobile ecosystem—one functions as a persistent identity tool for marketers, while the other acts as a necessary routing mechanism for network communication. While both are leveraged for tracking, they require different management strategies. For most users, the most robust privacy approach involves a layered defense: restricting app-level tracking permissions while simultaneously using IP-masking tools like a VPN or Private Relay. Recognizing that these identifiers operate on separate layers is the essential first step toward reclaiming control over your digital footprint.