What is the coolest free Web-API you used?

Question

I want to build some sort of showcase/tutorial project. Therefore, I look for a free API. Would love to work with something with geospatial data (e.g. live traffic data).What is the coolest free Web-API you came across so far?

calebkaiser · Accepted Answer

Not the coolest exactly, but I've used Unsplash's API to generate random high quality images for projects a surprising amount of times:https://source.unsplash.com/

What is the coolest free Web-API you used?

I want to build some sort of showcase/tutorial project. Therefore, I look for a free API. Would love to work with something with geospatial data (e.g. live traffic data).
What is the coolest free Web-API you came across so far?

Not the coolest exactly, but I've used Unsplash's API to generate random high quality images for projects a surprising amount of times:
https://source.unsplash.com/