I always consider it good practice to attach a source to an image. The internet is a public domain and almost everything on it lost it’s initial ownership right away.
However I’d like to think that with tumblr a gathering of kind, good-natured, creative souls that we make it a habit to put a source to our images whenever possible. Remember behind every cute pictures or cool drawings, there are people who put effort into it and they deserve every credit.
What is saucenao?
SauceNAO is a reverse image search engine. The name ‘SauceNAO’ is derived from a slang form of “Need to know the source of this Now!” which has found common usage on image boards and other similar sites.
How to use it is very simple
Go to saucenao.com. Upload your image and click get sauce.
It will give you the source and the link to the pixiv page.
If it’s a pretty old image, sometimes the image is already deleted or made private. You can credit the artist through the member page.
How accurate is it?
Granted this is not all-powerful and all-knowing that it’ll give you source for everything. But if it’s on pixiv, it’ll most likely find it.
If the image is heavily edited though (cropped, changed color), it will not find it.
I hope this will help all of you with difficulty finding a source for your image, photos, etc. Crediting the source with a link back is a form of respect to the creator.