• Applies to: TTF
• Fontspector can hotfix?: no
• Fontspector can fix sources?: no

OpenType fonts that contain TrueType outlines should use the value of 0x00010000 for the sfntVersion. OpenType fonts containing CFF data (version 1 or 2) should use 0x4F54544F ('OTTO', when re-interpreted as a Tag) for sfntVersion.

Fonts with the wrong sfntVersion value are rejected by FreeType.

https://docs.microsoft.com/en-us/typography/opentype/spec/otff#table-directory

• https://github.com/fonttools/fontbakery/issues/3388

• universal (in section 'Universal Profile Checks')

• googlefonts (in section 'Universal Profile Checks')