highlights

Advertising companies provide software development kits (SDKs) for mobile app monetization, which often automatically transmit users' location data to ad systems and location data brokers, raising privacy concerns. Many developers and users may be unaware of this data sharing. When developers allow SDKs to collect location data, it poses risks beyond targeted ads, including potential misuse by agencies like ICE and global surveillance. Location data brokers harvest precise movements of individuals, often without their consent, through mobile applications. Some apps directly collaborate with data brokers, while others leak data through advertising SDKs during real-time bidding (RTB) auctions. An incident in 2025 revealed that many apps unknowingly contributed to a location data broker's database. Developers must understand their SDKs' location-sharing practices to mitigate risks. Advertising SDKs can collect location data automatically once users grant permission, without specific permissions for the SDKs themselves. Precise location data can be collected when apps have location permissions, leading to potential privacy violations. Several SDKs have been identified as collecting location data by default, increasing the risk of unintentional data leaks. The Electronic Frontier Foundation (EFF) found that four advertising SDKs collect users' location data by default when location permissions are granted. InMobi encourages location sharing for higher revenue, while BidMachine updated its documentation after EFF's inquiry, confirming precise location data collection. Verve's SDK also collects location data by default but presents a cautious narrative in its Play Store guidance. Huawei's SDK recommends obtaining location permissions to enhance revenue, with default location sharing occurring if permissions are granted. Location data can be shared without users' knowledge or meaningful consent, complicating informed consent issues. The focus on four SDKs does not imply that others adequately protect location data, as many have faced criticism for similar practices. Studies indicate that SDKs often encourage increased data collection through design and documentation, leading to minimal control for developers over data transmission. The EFF's analysis highlights that advertising SDKs incentivize location data sharing through default settings and unclear documentation. Developers should assess third-party SDKs and disable unnecessary data collection. Regulators must hold developers accountable for unlawful data sharing, while legislators should enact laws to protect location privacy and address online behavioral advertising, which drives data tracking.