November 25, 2017 — Last week I explored the question "how many programming languages are there in the world?". My current estimate is between 5,000 and 25,000 active computer languages.

But perhaps the number is higher, if you include all active external web APIs.

What do other people say?

Programmable Web - 18,409

The site Programmable Web lists 18,409 web APIs. But figuring out which ones are used most is a work in progress.

RapidAPI - 7,500

RapidAPI lists over 500 APIs, but that should expand as it completes its acquisition of the Mashape Marketplace, which listed over 7,500 APIs.

Zapier - 750+

Zapier lists over 750 APIs.

Other Lists

On GitHub user abhishekbanthia maintains a popular list of about 300 apis. Wikipedia has a small list of about 30 APIs.

What do I say?

My estimate is: between 2,000 and 25,000 active public facing web APIs.

Reproducibility Notes:

My ad hoc estimates are based on checking the PLDB database, the datasets listed above, and additional web sources.