glyphIgo is a swiss Army Knife of fonts in ePub. It can do:
1. List all Unicode characters used in an EPUB file or a plain text UTF-8 file.
2. List all Unicode glyphs present in a TTF/OTF/WOFF font file.
3. Check whether a given font file contains all the glyphs needed to properly display the given EPUB or plain text file.
4. Minimize a given font file, that is, create a new font file containing only the subset of glyphs of a given font that are contained in a EPUB or plain text file.
5. Convert a font file from/to TTF/OTF/WOFF format.
6. Export one of the above lists of Unicode characters as an EPUB file, for quick testing on an eReader.
For more see:
https://www.mobileread.com/forums/sho...d.php?t=205979