This article explains what file formats use the GRD file extension and how to open or convert your file.
Convert IMD rasterized (.GRD) binary weather data to csv/excel using Python and QGIS
A file with the grd file extension may be an Adobe Photoshop gradient file. These files are used to store presets that define how multiple colors should blend together. Use one to apply the same blending effect to multiple objects or backgrounds.
Some GRD files may instead be Surfer grid files, a format used to store map data in a text or binary format. Others may be used as encrypted disk image files in PhysTechSoft's StrongDisk software.
GRD files can be opened with Adobe Photoshop and Adobe Photoshop Elements. By default, the built-in gradients that come with Photoshop are stored in the program's installation folder under the Presets/Gradients folder. This is usually in a folder like this:
