d2-rs: a Rust port of D2 with byte-identical output (CLI and WebAssembly)

[nelsonjchen]

Hi all! I've been working on d2-rs, a Rust port of the D2 toolchain: the compiler, the Dagre, ELK and TALA layouts, the SVG renderer, PNG/PDF/PPTX/GIF export and the d2 CLI. It also builds as a WebAssembly package.

_{Rendered by d2-rs itself with TALA and the new `--isometric` mode from D2 master (not in a D2 release yet)}

The goal is identical output, not "close enough". Upstream's own tests are the oracle:

• All 944 e2e golden boards match Go D2 master (6a7b483) byte for byte, across all three layout engines.
• The e2etests-cli suite passes, and differential runs on mutated inputs agree with Go.
• Faster than Go D2 on every e2e case, with lower peak memory on the median (about 0.2x Go's wall time for Dagre/ELK, about 0.5x for TALA).
• The WASM module is about half the size of d2js and about 3x faster, with the same compile / render API shape.
• Qualified on arm64 and x86-64; Windows passes natively.

Try it:

cargo install d2-rs
d2-rs input.d2 output.svg

npm install @d2-rs/wasm

A note on how it was made: over about two months (September to early November 2026), most of the code was written by AI coding agents: OpenAI Codex for the first six weeks, then Claude supervising Codex. They worked against D2's test suites, and a change only landed if every golden stayed byte-identical. The README has the details, plus a list of known issues found by going beyond the upstream corpus.

It's an independent, unofficial project: not part of D2 or endorsed by its maintainers. It's MPL-2.0 like D2. If you'd rather it not use the D2 name, I'm happy to rename it.

Thanks to the D2 team for the language, and for a test suite thorough enough to make this possible.