brepjs vs OpenSCAD

OpenSCAD is how a lot of people discover code-first CAD: free, focused, and around for over fifteen years, with an enormous community behind it. brepjs is a different kind of tool — a TypeScript CAD library with an exact B-Rep kernel (OpenCascade), running in the browser and Node.

They overlap (both build parametric models from code), but they're built for different jobs. This is an honest comparison: where each fits, and where OpenSCAD is still the better choice.

In short

• Reach for brepjs if you need exact geometry and STEP export for manufacturing or professional CAD, real fillets and chamfers on arbitrary edges, a real programming language (TypeScript — types, npm, normal control flow), or you want to embed a parametric configurator in a web app.
• Stick with OpenSCAD if you're making parts to 3D-print, you value a free tool with a gentle learning curve and a massive library ecosystem, you want non-coders to tweak models with sliders, or you simply already know it and it's working.

OpenSCAD isn't outdated — with its Manifold backend it's fast, and for hobbyist printing it's hard to beat. brepjs is for when you've hit its edges: exactness, STEP, fillets, and a real language.

Side by side

	brepjs	OpenSCAD
Geometry	Exact B-Rep (OpenCascade) — NURBS, exact surfaces	Mesh / CSG (Manifold) — triangle output
Language	TypeScript — types, npm, normal control flow	Its own DSL — immutable vars, single-expression fns
Fillets / chamfers	Real, on arbitrary edges	None native; minkowski/hull or BOSL2 (faceted)
Exact export (STEP)	STEP, IGES (+ STL, glTF, DXF, 3MF, OBJ)	None — mesh only (STL, OBJ, 3MF, AMF; 2D DXF/SVG)
Form factor	A library you embed (browser + Node)	A desktop app
Render speed	Fast (OpenCascade WASM)	Fast (Manifold backend)
Cost	Free (Apache-2.0)	Free (GPL)
No-code tweaking	Build your own web UI	Built-in Customizer — sliders, no code
Maturity	Newer	15+ years, very mature
Community & ecosystem	Growing	Huge — BOSL2, Thingiverse / Printables
Learning curve	Steeper if you're new to TypeScript	Gentle; no programming background needed

The bold rows are the honest summary: OpenSCAD leads on maturity, ecosystem, the no-code Customizer, and gentleness; brepjs leads on exact geometry, STEP, real fillets, and being a TypeScript library. Speed and cost are a wash — both are fast, both are free.

Where brepjs is different

Exact geometry and STEP export

This is the clearest divide. OpenSCAD produces a triangle mesh, and every 3D export (STL, OBJ, 3MF) is that mesh. brepjs produces an exact B-Rep solid and exports STEP — so the geometry round-trips cleanly into SolidWorks, Fusion, Creo, and CAM. An STL exported from OpenSCAD into a professional CAD tool is a lossy approximation; a STEP file is the real thing.

Real fillets and chamfers

OpenSCAD has no native fillet. People round geometry with minkowski() (slow, and dimensions shift), hull(), or the BOSL2 library — but those round shapes as you build them and produce a faceted mesh; you can't select an arbitrary edge of an existing solid and fillet it. brepjs has first-class fillet, chamfer, and shell that operate on real edges, and fallible operations return a Result so a failure is something you handle rather than a silently wrong mesh. (B-Rep fillets can still fail on tricky geometry — brepjs's value is real edge selection plus explicit error reporting, not a promise that every fillet succeeds.)

A real programming language

OpenSCAD's language is a domain-specific one: variables are immutable, functions are single-expression, there are no while loops or structs. It's elegant for small parts and awkward as models grow. brepjs is TypeScript — real types (branded Edge, Wire, Face, Solid), ordinary control flow, and the whole npm ecosystem.

A library, not an app

OpenSCAD is a desktop application that compiles a script to a mesh. brepjs is a library you import into a browser or Node project, so you can ship a parametric configurator as a web app. (OpenSCAD has an experimental WebAssembly build, but it's the whole app compiled to the browser, not an API you embed.)

A quick contrast

// OpenSCAD — its own language, mesh output, no native fillet
difference() {
  cube([30, 20, 10]);
  translate([15, 10, -1]) cylinder(r = 4, h = 12);
}
// Rounding that top edge means minkowski() or a library — and a faceted result.

// brepjs — TypeScript, exact B-Rep, a real fillet, and STEP out
import { box, cylinder, shape, exportSTEP, unwrap } from 'brepjs/quick';

const part = shape(box(30, 20, 10))
  .cut(cylinder(4, 12, { axis: [0, 0, 1], at: [15, 10, -1] }))
  .fillet((e) => e.inDirection('Z'), 2).val;

unwrap(exportSTEP(part)); // exact geometry for SolidWorks / Fusion / CAM

When OpenSCAD is the better choice

A fair comparison has to say this plainly — OpenSCAD wins in real situations:

• You're 3D-printing, not manufacturing. If a mesh is the final output, B-Rep and STEP buy you nothing.
• It's free and gentle. No JavaScript toolchain, no types to learn — a great on-ramp to code CAD.
• The ecosystem is enormous. BOSL2, threads and gears libraries, and thousands of ready-made parametric models on Thingiverse and Printables.
• The Customizer. OpenSCAD generates a slider/dropdown UI from your script parameters, so non-coders can tweak and download a model. brepjs has no built-in equivalent — you'd build the UI yourself.
• It's fast. The Manifold backend made rendering quick; speed is no longer a reason to leave.

If you're printing parts, want a free tool, or need non-coders to customize models, OpenSCAD is an excellent choice and brepjs is probably the wrong tool.

Already using OpenSCAD?

brepjs can't read .scad files — it's a different language — but the concepts map closely. The Coming from OpenSCAD guide has the operation-by-operation translation (union/difference → fuse/cut, for-loops → linearPattern/circularPattern, minkowski → real fillet), plus a side-by-side parametric bracket.

Choosing among JavaScript CAD libraries specifically? See brepjs vs Replicad.

FAQ

Can brepjs import my OpenSCAD files? No — OpenSCAD's language is its own, so you reimplement the model in TypeScript. The migration guide has the operation map; for trivial models it's a quick translation.

Can it still export for 3D printing? Yes — brepjs exports STL and 3MF for slicers, alongside STEP for manufacturing.

Do I need to know JavaScript? Yes. brepjs is a TypeScript library. If you don't write JS/TS and just want to print parts, OpenSCAD or a GUI tool is likely a better fit.

Is it free? Yes. brepjs is open source under Apache-2.0; OpenSCAD is GPL. Both are free.

Is brepjs production-ready? It's newer than OpenSCAD, with a smaller ecosystem, but it's well tested and grew out of a tool people use daily (the Gridfinity Layout Tool). For exact, manufacturable parts it's solid.

Try it

• Open the Playground — write TypeScript, see the solid, export STEP. No install.
• Get started — install and initialize in your own project.
• Coming from OpenSCAD — the operation-by-operation bridge.