Fontforge Variable Font Plugin

A FontForge_plugin to create a variable font

As of October 2025, Fontforge supports legacy (maybe obsolete) multiple master formats but not yet OpenType variable fonts. This plugin adds frontend of fontmake and fonttools so that variable fonts can be created through Fontforge interface.

This module can also export to WOFF2; in this case the woff2 tool will be used as backend.

This module requires Python 3.10 or later.

Install

pip3 install fontforge-variable-font

Make sure Fontforge Python module is usable

In interactive mode of Python, run:

import fontforge

If it raises ModuleNotFoundError exception, install Fontforge first. If installed, make sure the build option set that the Python module gets also installed. If already so, Python interpreter does not recognize the module path where the required module.

export PYTHONPATH=/path/to/fontforge/python/module:$PYTHONPATH

Usage

Interactive usage

As a Fontforge plugin, fontforgeVF adds 'Variable Font' submenu to 'Tools' menu which is dedicated for plugins.

Variable Font
- Open a variable font
  - By named instance...
  - By parameter...
- Generate a variable font...
- Design axes...
- Named instances...
- Delete VF info

Open a variable font

Shows a dialog to open a variable font

By named instance

Open file dialog is shown first. If a variable font is selected, then another dialog is shown to select (one or more) named instances. If a non-variable font is selected, simply opens that font.

By parameter

Like above, but the second dialog is not to select a named instance, but to specify design axis parameters.

Generate a variable font

Shows a dialog where you can set output file name and other options.

In order to build a variable font, SFD must be converted into UFO and create a designspace document. This plugin will do this first, and then required modification. The required files will be created in a temporary directory, and deleted after everything is done. So users won't see intermediate files.

Fontforge may export with postscriptIsFixedPitch flag clear when it should be set. The plugin checks if monospaced font is intended and fix the flag. Unlike Fontforge itself, only U+0020 to U+007E will be checked their width, because combining marks may have zero width even for monospaced fonts.

In a feature file, 'aalt' feature is specially treated. Fontforge may export incompatible 'aalt' feature (concretely 'script' or 'language' instructions must not be included unlike other features.) This function fix this first.

Currently available options:

Remove nested refs: Tell fontmake to decompose nested references into simple ones. Nested references are known to cause problems in certain environments.
Add 'aalt' feature: Calculate and output 'aalt' feature to UFO.

Design axes

Shows a dialog where you can set design axes.

This master

This section is needed for all masters.

For active font as one of VF masters, sets position in each design axis of VF master. Leave unset for unused axes. Registered axes can use default values which refers font properties.

Italic: default value is whether font.italicangle is negative. This axis is boolean: you choose the master is for italic or not. Seldom used together with slant axis.
Optical size: can default to font.design_size. Set in points. Must be positive.
Slant: can default to font.italicangle. 0 if upright, negative if oblique. This value is hardly positive (left-slanted.)
Width: can default using font.os2_width. 100 if normal width, less if condensed, greater if expanded. Must be positive.
Weight: can default to font.os2_weight. 400 if regular weight, 700 if bold. The minimum is 1 (hairline thin) and the maximum is 999 (extreme bold.)
Custom axes: there is a room for 3 user-defined axes. No default values.