I have a client that wants to reduce font file size. I would like to get rid of characters like ΔΩμπ£¥∏∑√∂µ. Most of these characters are included in the MacOS Roman or Windows 1252 codepages. I have some vague memory that says "that it's not allowed to remove those or the font might have issues being recognized on older systems".
Will I run into any issues if a web font doesn't include those characters? Or a otf font in Windows Office?
Thanks in advance!
I would be wary about not including £ and ¥ since those are major currency symbols, but most of the others you identify could be left out simply by not aiming to support the Mac Roman codepage but instead just targeting Windows CP1252.
What about including the glyphs but keeping them empty?
I thought about inserting a simple notdef inside those glyphs (a notdef drawing has less contours than those real glyphs, so it is less file size in the end).
For example, InDesign will normally display missing characters using a notdef—plus a bright pink highlight. Users who quite reasonably expect that highlight will be confused and might just miss the notdef if they don’t realize you have changed the rules.
Yes, SOME app or environment may expect certain characters. As you already have them, your best solution for such cases is… include those characters. But as noted, these are mostly not particularly critical or general-use, except the currency symbols.
Plus, unless your font is extremely unusual, the notdef won’t take up that much less space than the glyphs. Increment and product are definitely going to be smaller with the actual glyph!
But if it is for a client it is easy to verify. Just send them the font and let them test.
Terminological nit: Unicode doesn't have code pages. It might be more accurate to say that Unicode is a code page, though "code page" is generally not used in relation to Unicode, unless you're talking about the legacy mess it replaced.
Unicode does have blocks. But it's not necessarily good to think of blocks as chunks to be supported all or none.