The indicator “Cities with the Largest Facebook Ad Audiences” measures the estimated number of Facebook users in major global metropolitan areas who can be reached through paid Facebook advertising. It offers insight into the scale of digital engagement and market potential within these cities. The data is divided into two categories: “City Only” represents users residing strictly within the administrative boundaries of a city, while “City +40km” includes users located within a 40-kilometre radius of the city’s centre. This distinction enables a nuanced understanding of urban versus peri-urban digital audiences.

The indicator is particularly useful for advertisers and marketers seeking to tailor campaigns based on geographic concentration and digital penetration. For instance, campaigns focused on dense urban cores may rely on “City Only” data, while broader regional campaigns may benefit from the “City +40km” category. Researchers can also use the indicator to study patterns of digital connectivity, urban expansion, and tech adoption. In the context of the digital economy, this data serves as a proxy for understanding not just advertising reach but also the relative digital maturity and economic potential of global cities. Ultimately, it supports strategic planning across sectors that rely on location-based digital insights.