Firefox: If you frequently find yourself scouring image search sites to match images or see if they exist elsewhere, Image Search Options puts popular image search tools right in the Firefox context menu.
After installation whenever you right click on an image you'll be able to send the image link to image search sites like SauceNAO, IQDB, TinEye, GazoPa and Ascii2D. By default not all of the image search engines are enabled but a quick trip to the extension options menu allows you to enable them all in the main context menu or turn on a sub-menu to further organise them. Image Search Options also includes tools direct file transfer to image search hosts, handy for images buried in the background, behind login prompts or on your local machine.
Image Search Options is free and works wherever Firefox does.