When you use Google Image Search, you’ve always been able to search with an image by clicking on the camera icon.
That works fine and dandy, but what if you want to search with an image you find when browsing? You could right-click on the image, save it, then use the Google Image Search, but Google has a better way.
The Search by Image (by Google) extension, when installed, adds an option when you right-click on an image to search Google with that image.
It works really well. I used it to search this image on CNN:
And Google returned other images related to this conflict in Syria.