reverse-image
SauceNAO
The de-facto reverse-image search for anime, manga and fan art, indexing billions of images from sources such as Pixiv and Danbooru. Submit an image or image URL and it identifies where the artwork came from; there is a JSON API, but it requires a free registered key. Indispensable when you need to trace an illustration back to its original artist or first posting.
Why it’s useful & how it works
Free key (6/30s, 200/day). API CF-challenged without a valid key; page works via proxy. Clean JSON inline once keyed.
What’s inside
Billions of art images.
API access
https://saucenao.com/search.php?output_type=2&api_key= <KEY>&db=999&url=<IMG>
An API key is required — usually free; see the endpoints above for where to get one.
Access
Programmatic API access (a key may be required — see the API tag).