NeoSCAD

A new implementation of OpenSCAD, in Rust

OpenSCAD's language, rebuilt for speed and for agents.

NeoSCAD runs your .scad files and libraries as they are. It passes 1,773 of OpenSCAD's in-scope regression tests, and it is about 3.8× faster than the OpenSCAD nightly (Manifold) on heavy models.

macOS

Command-line tool brew install neoscad/tap/neoscad
App brew install --cask neoscad/tap/neoscad-app

The .dmg and more on the Download page

Linux

Install script curl -LsSf https://neoscad.org/install.sh | sh
Homebrew brew install neoscad/tap/neoscad

Flatpak app, .deb and .rpm on the Download page

Windows

Command-line tool scoop bucket add neoscad https://github.com/neoscad/scoop-bucket
then scoop install neoscad

The app and MSIs on the Download page

In the browser

OpenSCAD in your browser, at neoscad.org/try: NeoSCAD compiled to WebAssembly. Nothing is uploaded.

Downloads and status Connect your AI agent Try OpenSCAD in your browser

Bring your agent to the model. Claude Code, Cursor or any MCP agent can edit the model open in your browser, see the 3D view and point at what it means, while you watch.

NeoSCAD 0.2.1: a command-line tool for macOS, Linux and Windows (x86_64 and ARM), an app for macOS 15 or later (Apple silicon and Intel), and preview apps for Windows and Linux.

Built on the work of OpenSCAD, whose test suite is NeoSCAD's specification, and the Manifold geometry kernel. Credits.

A BOSL2 herringbone planetary gearbox on a gyroid plinth, rendered to STL in 1.77 s by NeoSCAD and 5.89 s by the OpenSCAD nightly 2026.09.23 with --backend=manifold: full render, best of 3, Apple M4 Pro. The model is apple/Icon/hero.scad in the NeoSCAD repository.

In numbers

  • 1,773 of OpenSCAD's in-scope regression tests pass. What's in scope?
  • ~3.8× faster than the OpenSCAD nightly (Manifold) on heavy models; 5.0× geometric mean over 14 models including startup, on an Apple M4 Pro. Method
  • ~0.25 s An edit to one part re-renders in about 0.25 s, in a warm neoscad serve (the planet carrier of the gearbox above; an edit to its gyroid plinth takes 1.55 s).
  • 3,569 BOSL2 example and test files, all giving the same echo output as the OpenSCAD nightly.

Benchmark

One chart, with its method

Bar chart of render times on a log scale for 14 models and a cold start, for NeoSCAD, the OpenSCAD nightly with Manifold, the nightly with CGAL, and OpenSCAD 2021.01. NeoSCAD is fastest on every row; on the 14 models its speedup over the nightly with Manifold ranges from 1.80× (Menger sponge) to 19.71× (BOSL2 fractal tree). Full numbers are in the table on the benchmarks page.
Wall time of -o out.stl for 14 models, including process startup; best of 3; one Apple M4 Pro (14 cores, 48 GB, macOS 27.0); the NeoSCAD 0.3.1 release binary against the OpenSCAD nightly 2026.09.23. The geometric mean is 5.0× against the nightly with Manifold. Nine of the 14 models finish in under 0.11 s, where startup counts for a lot: with startup subtracted it is 3.8×, and over the three models that take longer than 0.3 s, 6.4× (one of them, the BOSL2 fractal tree, is 20×). The nightly's times come from a cache measured with the same, SHA-pinned binary. Full table, method and caveats.

What it's for

Three things NeoSCAD is built to do

Your models, unchanged

Open your existing .scad files. NeoSCAD reads OpenSCAD's language and uses OpenSCAD's own regression tests as its specification. MCAD and OpenSCAD's default Liberation fonts are built in, and BOSL2 works from your library path, as it does in OpenSCAD.

Live editing

neoscad serve keeps a model warm and re-renders only what an edit changed: about 0.25 s for an edit to the carrier of the gearbox above. The macOS app is built on the same engine, and neoscad lsp brings diagnostics and completion to any editor that speaks the Language Server Protocol.

Built for agents

An MCP server (neoscad mcp), JSON output from every command, and tools an agent can look through: snapshot renders a dimensioned four-view sheet, measure and check report sizes and printability. Resource limits stop a runaway model with an error instead of filling the machine.

Set up the MCP server with Claude Code, Cursor or any agent.

Before you print

Check a model for printing

neoscad check renders the model and reports what would go wrong on an FDM printer, each finding with where it is and how to fix it:

  • a solid that isn't manifold, or breaks when written at STL's 32-bit precision;
  • pieces floating above the bed, and surfaces that would print fused;
  • walls thinner than the nozzle or your minimum wall;
  • overhangs steeper than your limit;
  • parts that intersect, and a model that doesn't fit your bed.
neoscad check part.scad \
  --nozzle 0.4 --min-wall 1.2 \
  --bed 256x256x256
neoscad snapshot part.scad --issues

snapshot --issues paints the findings onto the sheet: thin walls red, overhangs amber, floating pieces purple, with a numbered marker at each one. Add --format json for machine-readable output.

A NeoSCAD snapshot sheet of a yellow threaded hose-barb adapter in four views, iso, front, top and right, on a grid, with dimension lines: 34.64 by 30 by 45 mm, volume 12,123.82 cubic millimetres, 19,840 triangles.
neoscad snapshot of a threaded hose-barb adapter: four views with dimensions, one PNG an agent can read.
A NeoSCAD snapshot sheet with check findings marked on a phone stand in four views: the front lip drawn red as a wall 0.3 mm thick, a cable clip drawn purple as a piece floating above the bed, and numbered markers on the lip, the clip and an unsupported shelf. The header reads check: 2 errors, 2 warnings, with a legend for thin wall, overhang and floating.
neoscad snapshot --issues of a phone stand with three printing problems: a 0.3 mm lip (red), a floating clip (purple) and an unsupported shelf (marker 3).

Built in the open

How NeoSCAD was made, and how it's checked

NeoSCAD was written by AI coding agents. Almost all of its code was written by Anthropic's Claude, working as coding agents under the direction of one person, who set the plan, reviewed each change and committed it. The first commit is from 25 September 2026, and the full history is public, with each change and the tests it had to pass. Built by Matt Robinson with Claude, supported by The Ned Workshop.

You shouldn't have to trust it because of who, or what, wrote it, so its behaviour is checked against OpenSCAD's:

  • OpenSCAD's regression suite is the specification. 1,773 in-scope tests pass, and a change may not make a passing test fail.
  • BOSL2: all 3,569 example and test files give the same echo output as the OpenSCAD nightly, and BOSL2's own 976 tests pass.
  • Differential tests compare NeoSCAD's parse tree, echo and CSG output with the nightly's, and every benchmark model's mesh with the nightly's (volume, area and bounding box).
  • Fuzzing: the polygon tessellator was fuzzed against OpenSCAD's C libtess2, and an evaluator prototype against the tree-walking evaluator.

The source is at github.com/neoscad/neoscad, under GPL-2.0-or-later, OpenSCAD's licence.

Every recorded conformance run, from the first on 26 September 2026: the grid of OpenSCAD's tests, the commit that ran them, and the pass count over time. It is generated from the project's run log by conformance video.

Coming from OpenSCAD

What's the same, and what isn't

The language, the libraries and the command line (neoscad model.scad -o model.stl) work as you know them. The differences today:

  • Geometry uses Manifold only; there is no CGAL backend.
  • text() uses the bundled Liberation fonts; system fonts aren't found yet.
  • The macOS app has no Animate panel, and the customizer is partial.
  • We don't know of a model where it is slower than the nightly, but we have measured only so many; if you find one, please open an issue.
  • The Windows and Linux apps are still previews, though since 0.2.1 they have the macOS app's check, measure and customizer panels too.

NeoSCAD is an independent project. It is not affiliated with or endorsed by the OpenSCAD project.

Credits

Standing on OpenSCAD and Manifold

NeoSCAD exists because of OpenSCAD: its language, its examples and, above all, its regression test suite, which is NeoSCAD's specification. Thank you to its maintainers and contributors.

Geometry is Manifold, by Emmett Lalish and contributors, through Lars Brubaker's Rust port, manifold-rust. Manifold is also what makes the OpenSCAD nightly fast.

Also: Clipper2, through Lars Brubaker's clipper2-rust; libtess2 (Mikko Mononen's packaging of the SGI GLU tessellator); BOSL2 by Revar Desmera and contributors; MCAD; and the Liberation fonts.

Supported by

NeoSCAD is free and open source. If it's useful to you, you can support its development. Donations go to The Ned Workshop, a 501(c)(3) nonprofit, and are tax-deductible in the US. Donate

Questions

Why not CadQuery or build123d?

They're good tools. They are Python libraries on a B-rep kernel, so they give you fillets on real edges and STEP output, which NeoSCAD, a mesh modeller like OpenSCAD, does not. NeoSCAD is for people and agents who already have OpenSCAD models and libraries such as BOSL2, or who want OpenSCAD's small declarative language and a fast edit-and-see loop.

Is it a drop-in replacement for OpenSCAD?

Not a claim we make. OpenSCAD's suite registers 3,258 tests. In the latest run 1,773 pass and 1,485 are skipped as out of scope: duplicates that only run on the CGAL backend (NeoSCAD uses Manifold only), experimental features, and tests that OpenSCAD itself marks as known bugs or disabled. The GUI is less complete than the command line.

Is it faster on every model?

On every model we have measured, but not by the same amount. On the 14-model benchmark it is about 3.8× faster than the nightly with Manifold on the heavy models, and 5.0× as a geometric mean including startup; the smallest lead is 1.80×, on the Menger sponge. We don't know of a model where it is slower; if you find one, please open an issue. The benchmarks page has every number.

Which platforms does it run on?

The command-line tool runs on macOS, Linux (glibc 2.28 or later) and Windows, on x86_64 and ARM. The app needs macOS 15 or later, on Apple silicon or Intel. It also runs as WebAssembly, with nothing to install: OpenSCAD in your browser. See downloads.

Who wrote it?

AI coding agents, directed by one person. How it was made and how it's checked covers it.