Nik Collection

Starting March 24, 2016, the latest Nik Collection was made freely available to download: Analog Efex Pro, Color Efex Pro, Silver Efex Pro, Viveza, HDR Efex Pro, Sharpener Pro and Dfine.

However, in 2017 it was announced that the Nik collection is longer supported and will not be added to or updated.

https://www.google.com/nikcollection/