Jakarta, Indonesia's sprawling capital, has officially overtaken Tokyo to become the world's most populous city, with approximately 42 million residents—roughly the same as Canada's entire population. The United Nations Department of Economic and Social Affairs' "World Urbanization Prospects 2025" report, released in November, revealed this dramatic shift, moving Jakarta from 33rd place in 2018 to the top spot in 2025. Dhaka, Bangladesh's capital, claimed second place with 37 million people, while Tokyo fell to third with 33 million.​

The Methodology Behind the Numbers

The significant leap in Jakarta's ranking stems mainly from a revised UN methodology for measuring urban populations. Previously, population estimates relied on varying national statistics, creating inconsistencies in how different countries defined urbanization. The new standardized approach classifies cities based on continuous agglomerations of one-kilometer-square cells that meet minimum density thresholds and have a total population of at least 50,000 people. This uniform framework better captures Jakarta's actual metropolitan footprint, which extends far beyond its core province of DKI Jakarta—home to over 11 million people—to encompass the broader Jabodetabek region with more than 40 million residents.​

A Megacity Under Pressure

Jakarta's explosive growth reflects a broader global urbanization trend, with cities now housing 45 percent of the world's 8.2 billion people, up from just 20 percent in 1950. The number of megacities—urban areas with populations exceeding 10 million—has quadrupled from eight in 1975 to 33 in 2025, with 19 located in Asia. However, Jakarta's ascent comes with severe environmental and infrastructure challenges that threaten its long-term viability.​

The city is literally sinking, with ground levels dropping between 3 and 10 centimeters annually due to excessive groundwater extraction. Approximately 40 percent of Jakarta already sits below sea level, and projections suggest up to a quarter of the city could be submerged by 2050. North Jakarta has sunk 2.5 meters in the last decade alone—twice the global average for coastal megacities. With limited access to reliable piped water, millions of residents and businesses continue pumping from underground aquifers, accelerating land subsidence and causing saltwater intrusion into freshwater supplies.​

Traffic, Inequality, and Environmental Crisis

Jakarta's infrastructure struggles to support its massive population. The city experiences some of the world's worst traffic congestion, with drivers spending more than a quarter of travel time idling and averaging 33,000 stops and starts annually—the highest globally. Traffic jams cost Jakarta an estimated $5 billion per year in fuel consumption, vehicle operation costs, time value, and air pollution. Over 22 million registered vehicles overwhelm limited road networks that haven't kept pace with population and economic growth.​

A New Capital on the Horizon

In response to these mounting pressures, the Indonesian government is constructing Nusantara, a new capital city in East Kalimantan province on Borneo Island. The $35 billion project, expected to be completed by 2045, aims to relieve Jakarta's burden by relocating government functions to a more sustainable location less vulnerable to natural disasters. Despite this effort, the UN forecasts an additional 10 million people will still reside in Jakarta by 2050. As Dhaka is projected to surpass Jakarta as the world's largest city by mid-century, the challenges facing megacities in developing nations will only intensify, demanding innovative solutions to balance growth with sustainability and livability.