glyphsLib

6.13.0 verified Mon Apr 27 auth: no python

A Python library that bridges Glyphs source files (.glyphs) to UFOs (Unified Font Object) and back. It converts .glyphs files into UFO packages for further processing (e.g., with fontmake) and can also write back to .glyphs format. The current version is 6.13.0, with a relatively active release cadence (multiple minor releases per year). Requires Python >= 3.10.

pip install glyphslib

Common errors

error ModuleNotFoundError: No module named 'glyphslib' ↓

cause The library is not installed, or you used the wrong import name (e.g., 'glyphslib' instead of 'glyphslib').

fix

Run pip install glyphslib and ensure correct spelling: import glyphslib.

error AttributeError: module 'glyphslib' has no attribute 'load' ↓

cause You might be using an older version of glyphsLib (pre-6.0) where the load function was in a submodule.

fix

Upgrade to glyphsLib >=6.0: pip install --upgrade glyphslib. Or use from glyphslib.glyphs import load for older versions.

error glyphslib.builder.BuildError: Unsupported custom parameter: ... ↓

cause The .glyphs file contains a custom parameter that glyphsLib does not understand or implement.

fix

Check the parameter name and report an issue. Often it can be safely ignored by passing ignore_unknown_parameters=True (if available) or by removing the parameter from the .glyphs file.

Warnings

breaking Version 6.0.0 dropped support for Python 3.9 and earlier. If you are on an older Python, you must use an older version of glyphsLib. ↓

fix Upgrade to Python 3.10+ or pin to glyphsLib <6.0.0 (e.g., pip install 'glyphslib<6').

gotcha The .glyphs file format (v2 vs v3) is auto-detected, but some custom parameters or new features in Glyphs 3 may not be fully supported. Always check for warnings or errors during conversion. ↓

fix Use the `validate` function or inspect the logs for unsupported features.

deprecated The `glyphslib.glyphs` submodule (direct .glyphs file parsing) is being deprecated in favor of the higher-level API in `glyphslib` package itself. ↓

fix Use `from glyphslib import load` instead of `from glyphslib.glyphs import load`.

gotcha When converting back to .glyphs (using `to_glyphs`), some UFO features like kerning exceptions or OpenType lookups may not round-trip perfectly. Always verify output. ↓

fix Check the generated .glyphs file in Glyphs.app for fidelity.

Imports

GlyphsFile
wrong
```
from glyphslib.glyphsfile import GlyphsFile
```
correct
```
from glyphslib import GlyphsFile
```
In older versions, GlyphsFile was under glyphslib.glyphsfile; now it's exported at package level.
load
wrong
```
from glyphslib.load import load
```
correct
```
from glyphslib import load
```
The load function is directly in the top-level package.
to_ufos
wrong
```
from glyphslib.builder import to_ufos
```
correct
```
from glyphslib import to_ufos
```
The to_ufos function is exported from glyphslib directly, even though the implementation is in glyphslib.builder.

Quickstart

Load a .glyphs file and convert it to UFOs using the high-level API.

from glyphslib import load, to_ufos

# Load a .glyphs file
glyphs_data = load('MyFont.glyphs')

# Convert to UFO fonts (list of UFO objects for each master)
ufo_fonts = to_ufos(glyphs_data)

# Now you can work with UFOs using fontTools or ufoLib2
for ufo in ufo_fonts:
    print(ufo.info.familyName)