CaptionBot.ai is powered by machine learning technology that identifies and captions your photos. When you upload a photo, it is sent to Microsoft for image analysis to return a caption. We won’t store, publish, or let other people use your images.
I uploaded a few images. It works pretty well.
I'm unsure of this particular bot's purpose but you can likely see its cousin running in Windows 10's Photos app - that will automatically discover things like mountains, rivers, dogs, etc. in photos.
Google, Apple, Facebook all have similar technology for discovering things or people within images. I believe the only ones that do this on device, though, are Apple and Microsoft. The others rely on the image making it to cloud servers to be "scanned".
/via James Gurney.