Q: What is reverse image search?
A: With normal image search you enter words to find images. With reverse image search you enter an image to find others like it. Another name for this type of search is "similar image search".
Q: Why the name "Karma Decay"?
A: Firstly, I thought the name just sounded cool. I got it from this comment on Reddit.
Secondly, the name comes from the following observation:
The potential karma for any image decays with each subsequent post.
As an image is posted more and more times on Reddit, the chance that it will get up-votes is reduced; less votes means less karma. This is based on averages; exceptions occur.
Q: Why is Karma Decay different than TinEye.com or other reverse image search engines?
A: Sites like TinEye and Google attempt to index the entire Internet. Karma Decay indexes only Reddit.com. This specialization allows Karma Decay to offer speed and features that no one else does.
Q: I know this picture was posted before, why didn't Karma Decay find it?
A: This website is beta. It has not indexed 100% of Reddit.
Karma Decay is less sophisticated than sites like TinEye.com. It is only good at finding "very similar" images. Images that have been greatly modified might not be found.