Font-specific metadata locations
SMuFL-compliant applications running on desktop operating systems such as Windows, OS X, or Linux need to be able to determine whether a given font installed on the system is itself SMuFL-compliant.
There is no simple way to encode this information in the font itself[^1], so instead applications should identify SMuFL-compliant fonts by the presence of the font-specific JSON metadata file in a known location.
It is recommended that, if possible, the font metadata is installed in a system-wide location that allows access by all users on the system:
- OS X:
On Windows, the
%COMMONPROGRAMFILES% environment variable expands to
C:\Program Files\Common Files, or its localised equivalent.
It is typically necessary to require administrator privileges to install files into these locations. However, it is also recommended that, if possible, fonts themselves should also be installed in system-wide locations, so if the metadata is installed by the same installer as the fonts, no additional privileges will typically be required.
If it is impossible or inappropriate to install the font metadata in a system-wide location, use a user-specific location instead:
- OS X:
%LOCALAPPDATA% expands to
On OS X and Linux,
~ is a shortcut to the current user's home folder, e.g.
/Users/<username>/ on OS X.
It is not typically necessary to require administrator privileges to install files into these locations. However, files installed in these locations will not be accessible to any other user account on the system.
If a font is not designed to be used outside of a particular, specific application, then of course it is not mandatory for it to be installed in a system-wide location, nor for its metadata to be installed in these publicly accessible locations: a private font intended for use within the confines of a single application may choose to install its metadata in any convenient private location.
Because font-specific metadata may be installed in either (or both) a user-level location or a system-level location, applications should give metadata found in the user-level location precedence over metadata found in the system-level location.
[^1]: None of the existing tables in TrueType or OpenType fonts lend themselves to storing arbitrary data that could be used to identify a SMuFL-compliant font without subverting the purpose of an existing field in a table, which could have unforeseen side effects.