# diffenator3

**Repository Path**: mirrors_googlefonts/diffenator3

## Basic Information

- **Project Name**: diffenator3
- **Description**: Diffenator2, but Rustier
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2024-07-19
- **Last Updated**: 2026-09-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Diffenator3

This is a Rust port of
[diffenator2](https://github.com/googlefonts/diffenator2), a utility for
comparing two font files. It comes in two flavours, command line and
WASM.

The _command line_ version compares two fonts and describes the differences
between them; it produces reports in text, JSON and HTML format. By default,
it compares variable fonts at their named instances, although you can also
ask for comparisons at specific points in the design space, at the
min/max/default for each axis or subdivisions in between, or at master
locations. See the `--help` documentation of `diffenator3` for more details.

You can customize the look and feel of the HTML report by editing the templates
in the `~/.diffenator3/templates` directory after running `diffenator3 --html`
for the first time. Additionally, you can supply a `--templates` directory for
per-project templates.

The _WASM_ version compares two font files over the web and displays a HTML
report of the differences. This runs the `diffenator3` code directly inside
your web browser - the fonts are *not* transferred across the Internet.
You can use the WASM version at
https://googlefonts.github.io/diffenator3

## diff3proof

As well as `diffenator3`, there is another utility called `diff3proof` used
to generate HTML proof files showing the difference between the fonts. It
also works on a single font with no "before" version to diff against, which
makes it useful when onboarding a brand-new font.

`--sample-mode` controls what the proof shows, and can be repeated
(comma-separated) to combine several sections on the same page:

- `context` (the default) shows paragraphs of sample text for each language
  supported by the font.
- `cover` shows a minimal text that covers all the shared codepoints in the
  font.
- `waterfall` shows the cover text at a ladder of point sizes, to help spot
  hinting/rasterization jumps. Sizes can be customized with
  `--waterfall-sizes` (comma-separated, in px; default
  `7,10,11,12,14,16,18,21,27,32`).
- `glyphs` shows every encoded glyph in the font, laid out in a grid.
- `spacing` shows curated strings that stress sidebearing consistency and
  kerning pairs (Latin only for now).

For example:

diff3proof --sample-mode context,waterfall,glyphs,spacing font.ttf


These can be helpful for manually checking rendering differences in
different browsers.

## Additional utilities

If you build `diffenator3` from source, there are three additional workspace
crates which build some utilities which are mainly helpful for working on
`diffenator3` itself:

- [`ttj`](ttj/) serializes a TTF file to JSON in much the same way that `ttx`
  serializes to XML. However, there is no deserialization back to TTF at
  present.
- [`kerndiffer`](kerndiffer/) is a limited version of `diffenator3` just for
  checking kerning differences. You can achieve much the same functionality
  with `diffenator3 --no-tables --no-words --no-glyphs`.
- [`rendertest`](rendertest/) is used to test the rendering and bitmap comparison
  functionality of `diffenator3`. It generates bitmap images of words in both
  fonts and then overlays them.

## Installing

Binary versions can be obtained from the latest GitHub release; development
versions can be obtained via the latest GitHub Action. The `diffenator3` and
`diff3proof` binaries are all you need - they contain all the templates and
wordlists within them - so you can copy them to anywhere in your path.

Alternatively you can install from source with
`cargo install --git https://github.com/googlefonts/diffenator3`.

## License

This software is licensed under the [Apache 2.0 License](LICENSE.md).