The biggest city in the world by population right now is generally considered to be Tokyo, Japan , with around 37 million people in its greater metropolitan area, though a recent UN-style estimate suggests Jakarta, Indonesia, has surged to around 42 million and may now rank first depending on how city boundaries are defined.

What “biggest city” really means

When people ask “what is the biggest city in the world” , they usually mean largest by population , not by land area.

However, even “population” can be measured in different ways, so rankings can change depending on which definition is used.

  • City proper : The population inside the official city limits (often smaller in spread‑out megacities).
  • Urban area : The continuous built‑up area, ignoring administrative borders.
  • Metropolitan area : The wider commuting region around a core city, usually producing the huge numbers used in “megacity” lists.

Most “biggest city in the world” lists use urban or metro population , which is why Tokyo and now possibly Jakarta dominate the rankings.

Today’s top contenders

The exact order shifts with new demographic reports, but recent data and analyses highlight a few mega‑giants at the top.

  • Jakarta, Indonesia – A UN‑type urbanization report in 2025 puts the Jakarta metro at about 42 million people , stating it has overtaken Tokyo as the world’s most populated city.
  • Tokyo, Japan – Many global rankings still list Tokyo around 37 million residents , calling it the most populous city in the world based on metropolitan population.
  • Delhi (New Delhi urban region), India – Often ranked second or third, with a rapidly growing metro population in the mid‑30‑million range in recent lists.
  • Shanghai, China – Another massive hub typically sitting in the top three to four by metro population, with tens of millions of residents.

Because different organizations use different boundaries and data years, you will sometimes see Tokyo still listed as number one , while newer, more aggressive urban‑area estimates now push Jakarta into first place.

Why sources disagree

Rankings are not identical across news sites, demographic portals, and UN‑linked reports.

  • Different cut‑off years : Some lists are labeled “2024” or “2025” but use data from earlier censuses and projections.
  • Different boundaries : Including or excluding surrounding satellite cities can change a city’s “population” by millions.
  • Rapid growth in the Global South : Cities like Jakarta, Dhaka, and Delhi are growing so fast that a ranking can change within just a few years or even between updates.

A recent article summarizing a UN‑style “World Urban Prospects 2025” report explicitly notes that Jakarta has now “surpassed Tokyo to become the most populated city worldwide,” with Dhaka close behind and Tokyo sliding to third , highlighting how dynamic these rankings have become.

Forum and “latest news” angle

In online discussions and forums, people still frequently answer “Tokyo” when asked which is the biggest city, and many reference lists and videos that rank Tokyo as number one with a metro population of roughly 37 million.

Newer urbanization news pieces and think‑tank summaries, though, are picking up the narrative that “the world has a new largest city” in Jakarta , reflecting updated UN‑style population estimates for megacities.

In short:

  • If you go by many classic population rankings, Tokyo is still the biggest city in the world.
  • If you follow the latest UN‑type megacity projections, Jakarta now edges into first place, with an estimated 42 million people in its wider urban region.

Note: Information gathered from public data and reports available on the internet and portrayed here.