• Internet Business, Ezine Publishing
• best app to open CU1 files
• June 2, 2026

A CU1 file is most commonly associated with PhotoLine, where it is used as a PhotoLine4 Curves Curve File. In this context, it is not a regular image file like JPG, PNG, or GIF. Instead, it is more like a saved adjustment or preset file that PhotoLine can use when editing images. The “curve” part refers to curve adjustments, which …