CMX is legacy and read-only here
CMX is an older vector format. It can usually be opened and converted from, but it's long obsolete, so there's no modern encoder to create new CMX files.
Looking for PNG to CMX? Here's why CMX isn't an output option — and the modern formats to use.
We don't create CMX files — it's a legacy format that's effectively read-only. Here's what to convert to instead.
CMX is an older vector format. It can usually be opened and converted from, but it's long obsolete, so there's no modern encoder to create new CMX files.
For a file that opens everywhere, convert your PNG to JPG, TIFF or WEBP instead.
PNG is a lossless raster format with full transparency. It keeps every pixel intact, making it ideal for logos, icons, screenshots and graphics with sharp edges.
How to open PNG opens in every browser and image viewer, plus Photoshop, GIMP, Preview and Photos.
Full PNG format guide