This is a Rust port of 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

As well as diffenator3, there is another utility called diff3proof used to generate HTML proof files showing the difference between the fonts. This can be used in two modes: --sample-mode context (the default), which shows paragraphs of sample text for each language supported by the font, and --sample-mode cover, which shows a minimal text to cover all the shared codepoints in the font. These can be helpful for manually checking rendering differences in different browsers.

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 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 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 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.

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.

This software is licensed under the Apache 2.0 License.