Contrary to popular belief, pictures found on Google Images are not free to use any way you want. Google has recognized this belief is widespread, so they have now implemented a new filter in their search results that will show you the images which are legal to use.

Using it is very simple. After entering your search term, click on the "search tools" option in the menu bar. That will drop down to reveal more options, including "Usage Rights". Then choose the license you are looking for, and the search results will update instantly. The first results are often from Wikipedia (or associated pages).

According to 9to5 Google, it is not clear how Google identifies which images are legal and which ones are not. But it's pretty safe to say that anything on Wikipedia is free to use, and with the rest, it would be good to cover yourself legally by linking to, and crediting, the image owner in your work. Eventually Google will probably clarify how it categorizes images which are free to use, and which ones are not.

Having a "Usage Rights" filter is not new. Yahoo has had this option for quite some time, with search results drawing upon their Flickr photo site. Nevertheless, it is good that the world's largest search engine has finally added the feature too. Now there is no excuse for stealing images from people, saying "...but...I didn't know!"

Source: 9to5 Google