From the About-page:
Photos for everyone
Over 3 million free high-resolution images brought to you by the world’s most generous community of photographers.
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Is it really free? Yes.
Unsplash is a platform powered by an amazing community that has gifted hundreds of thousands of their own photos to fuel creativity around the world. So sign up for free, or don’t. Either way, you’ve got access to over 3 million photos under the Unsplash license—which makes them free to do-whatever-you-want with.
So, I really like using Unsplash.
One thing I am always uneasy about is when I see just how many photos with people there are on the site. What model in their right mind would agree to give away their likeness for free and practically without being able to control the use of the resulting works at all?
Like, imagine a right-wing party uses you wearing a rainbow shirt as a motive in their campaign. And since the image is not individually licensed, there is pretty much nothing you can do.