How many online stores are there worldwide?

How to get close to this number

Count the platforms. A handful of hosted commerce services have millions of merchants each, and self-hosted shops add more on top. Summing the published merchant counts of the major platforms is how this estimate is actually built, and it lands in the tens of millions.

The distribution in the explanation is the entire point: fewer than a million generate more than a trivial amount of revenue a year. So the great majority of online stores are abandoned experiments, dormant side projects or shops that never made a sale. A count of stores measures how easy the software made it to start, not how many businesses exist.

That is the same shape as the games-on-Steam question on this site, and it is the defining pattern of every low-barrier platform: removing the cost of entry produces enormous supply with a tiny successful tail. As the explanation puts it, setting one up takes minutes and getting anyone to visit it is the entire business.