When I am creating a 3D scene, one of the most important aspects that I take into account right from the beginning is light. There are many ways to light up a scene starting by the traditional tools such as the daylight system, dome and spotlights. To be honest I left those a long time ago and only use for specific purposes. For me no lighting setup is complete without an HDRI. That said, in this post I put together some of my favourite HDRI map sites.
When it comes to free hdri maps, HdriHaven is one of the best websites out there. All the maps are 100 percent free, licenced under the Creative Commons and can be instantly downloaded. HDRIHaven offers high quality 16k HDRI maps which gives you high quality shadows, reflections and background. They have got a variety of maps going from Outdoor, Indoor, Skies and other categories ready.
HDRI-skies is another great source of HDRI maps, used by some of the most popular VFX companies for their projects for CG projects and Architecture Visualization. HDRI maps up to 2k resolution are available to download for free. All the HDRI maps can be used for commercial and non commercial purpose.
NOEMOTIONS HDRs is an excelent source of hdri maps. All the material that the creators provide is available for both personal and commercial work, free to download and licenced under Creative Commons. They have got a lot you can choose from such as day, evening and night hdri maps.
iHDRI is also another great source I recently came around. All the HDRI Skies available on the website are free, go up to 16K resolutions and licenced under Creative Commons, both for private and commercial works.