 <p>It's because the font is missing hinting, as already noted. Mac OS always strips away the hinting data anyway, as its rasterizer "auto-hints" the font itself.</p> <p>However, there is a great little software which uses the automatic hinting of FreeType and embeds the data into the file, i.e. it auto-hints the font for you.</p> <p>See here: <a href="http://www.freetype.org/ttfautohint/" rel="nofollow">http://www.freetype.org/ttfautohint/</a></p>