An NRW file is a raw image file produced by high-end Nikon COOLPIX and digital SLR cameras. It saves image data in an uncompressed format that can be processed on the camera or on a computer after the image is captured. NRF files are similar to .NEF files, but are designed to support Windows Imaging Component (WIC) functions.
NRW files are often rather large in size (typically around 22MB) since they store 12-bit RGB CCD-RAW camera information at a high resolution and are saved in an uncompressed format. Also, NRW files store image adjustments separately from the image data, meaning that changes to the image can be undone.