TinEye.com. This search engine’s sole function is to search for exact match images, including where it came from and how it’s being used, higher resolution images and also modified versions. Meranda Watling: "I searched for an image I pinned a year ago because it made me laugh (it’s a sign bashing another signmaker for using Comic Sans). I’ve seen it around the web for awhile but the link on Pinterest takes me to a Tumblr log-in page. TinEye turned up 57 results, which I can sort by best match, most changed (for example if someone crops, photoshops, etc.) and biggest image (if I wanted a higher resolution version)."
Google Images Search. You’ve probably used Google Image Search to track down images of places, people or things. But did you know you can search by an existing image instead of a name or word? Go to the Google Images search page. Instead of typing in a search term, click on the little camera icon. It will pop up and give you the option of either searching by an image at a certain URL or uploading an image to search by.
Both the URL and uploaded file work the same, basically scanning the web for images that are similar. Unfortunately, this doesn’t always turn up the original in the top results and sometimes the results for “visually similar” images are far far far off-base, but it at least can usually give you a feeler on whether it’s unique. I find it’s useful to skip the search results, and go to the image results with it set it to “more sizes” instead of “visually similar” (the more sizes options means it’s searching for different resolutions but exact copies of your image). You can use the search tools there to sort by the date range. If you get a bunch of results to wade through, you can set the date range to a specific period, so for example you could search the Sandy images with it set to before the storm to see if there are any hits.