NassLab · Browser-Based CAD · v4.7.0 · Single HTML File · Native CSG

NASSCAD — a real CAD tool in your browser

STEP · AP203 · AP214 · AP242

Exact analytical solids in your browser. Import, edit and export native STEP B-Rep — assemblies, colors, PMI and GD&T.

Launch NASSCAD → ⬇ Offline package — Windows x64 · 58 MB See what it does
!

Since V4.7.0 there is no WebAssembly fallback: boolean operations — Union, Subtract, Intersect — require the free MEDUSA companion engine (Windows x64, 20 MB, portable). Everything else — STEP AP242 import/export, the 18 primitives, the generators, NassScript and every export format — runs in the browser with nothing installed.

Claude Sonnet 4.6 — Anthropic
AI-assisted coding Claude Sonnet 4.6 · Anthropic
Free No install No account Offline-ready STL · OBJ · 3MF · GLB · PLY Manifold C++ CSG Tree NassScript WebGL
DRAG TO ORBIT · DOUBLE-CLICK TO RESET

NASSCAD v4.7.0 · STEP AP242 B-Rep · NassLab

// What is NASSCAD

A real CAD tool.
In your browser.

01

A real CAD tool in your browser

A full 3D parametric CAD application delivered as a single HTML file. No server, no account, no installation. Runs entirely in your browser via WebGL and WebAssembly — online or offline.

02

Built for makers and engineers

Designed for people who actually build things — FDM printing, CNC, mechanical assembly. Every primitive, every export format, every workflow decision was made to get from idea to slicer fast.

03

Scriptable from the ground up

NassScript exposes every internal function via an integrated JS console. Automate complex geometries, create procedural parts, chain boolean operations — all in the same window as your model.

// STEP AP242

STEP AP242 with PMI.
In one HTML file.

OpenCASCADE Technology compiled to WebAssembly — the same kernel as FreeCAD, running in a tab. No server. No plugin. No install.

📥

STEP AP242 Import

Multi-body assemblies AP203/AP214/AP242 — names, positions, colors preserved. Supports complex industrial assemblies.

📤

STEP AP242 Export

Analytical B-Rep export with assembly hierarchy. Exact geometry — not tessellated mesh. File size ÷429 vs faceted BREP.

🔄

Validated Round-Trip

Import → edit → export cycle validated with Fusion 360 and FreeCAD. What goes in comes out — exact, clean, compatible.

⚙️

OpenCASCADE WASM

OCCT kernel compiled to WebAssembly — the same engine powering FreeCAD and Siemens NX, embedded in a single HTML file.

Fusion 360 ✓ FreeCAD ✓ Autodesk Viewer ✓ AP203 · AP214 · AP242
// Core Features

Everything you need.
Nothing you don't.

Parametric modeling, boolean operations, advanced generators, memory management — inside a single file you can save to your desktop.

F-01

Boolean CSG — Manifold C++

Union, subtraction, intersection — powered by Manifold, the open-source C++ CSG kernel developed at Google. Since V4.7.0 it runs natively through the MEDUSA companion engine, multi-threaded with Intel TBB. Every boolean is logged in a re-runnable CSG tree.

F-02

Advanced Parametric Generators

ISO involute gears & V-groove pulleys (Gear.Gen), hollow curved pipes with Bishop-frame path (Pipe.Gen), parametric screws ISO 68-1 / UNC·UNF (Screw.Gen), parametric nuts ISO 4032/4033 · ASME B18.2.2 (Nut.Gen), ultra-HD torii, chamfered/rounded cubes, solids of revolution, spherical sectors, threaded fasteners.

F-03

Geometry Pool with GC

A 2 GB ArrayBuffer with a custom mark-and-sweep garbage collector handles all geometry and scene snapshots. BVH/AABB caching on every mesh keeps raycasting fast on complex scenes.

F-04

Full Scene Management

Solid/Hole mode per object for automatic boolean detection. Box-select for bulk ops. Live XYZ transform. Dimension annotations in 3D viewport. Project save/load as JSON.

F-05

Export Quality Control

STL export uses 128 segments by default — optimized for FDM. Quality slider goes higher for SLA or CNC. Hard-dimensions approach: what you model is what you export, 1:1, no scale surprises.

F-06

Import STL · OBJ · 3MF · GLB · PLY

File picker or drag-and-drop import. Imported meshes are first-class objects — boolean-combinable with native primitives, transformable, and re-exportable into any assembly.

F-07

STEP Assembly — OpenCASCADE WASM

Full STEP assembly import/export powered by OpenCASCADE Technology (OCCT) compiled to WebAssembly. Multi-body AP203/AP214/AP242 import — names, positions and colors preserved. AP242 B-Rep export with assembly hierarchy. Validated: Fusion 360 ✓ FreeCAD ✓

// Primitives & Generators

Start fast with
what you need

Core primitives are one click. Advanced generators open a live-preview modal with sliders. 18 watertight primitives total.

Cube Sphere Cylinder Cone Half-Sphere Tube Roof Arc ⚙ Gear.Gen — ISO Involute ⚙ Gear.Gen — V-Groove Pulley ⌁ Pipe.Gen — Bishop Frame ◎ Torus Ultra-HD ✦ Chamfered / Rounded Cube ⌾ Truncated Cylinder · Double Chamfer ⌀ RevSolid.Gen — Solid of Revolution ◑ ArcSphere.Gen — Spherical Sector 🔩 Screw.Gen — ISO 68-1 / UNC·UNF ⬡ Nut.Gen — ISO 4032/4033 · ASME B18 M Threaded Fastener
NassScript — Stellate Crown demo
// Clear scene objs.forEach(o => { scene.remove(o.mesh); o.mesh.geometry.dispose(); }); objs = []; updStats(); // Place central torus showToreDialog(); _toreRebuild(); await delay(300); _toreToScene(); // Orbit 6 spheres as holes const N = 6, R = 70; for (let i = 0; i < N; i++) { const a = (2 * Math.PI * i) / N; addPrimitive('sphere'); const o = objs[objs.length - 1]; o.mesh.position.set( Math.cos(a)*R, 8, Math.sin(a)*R ); setHoleMode(true); await delay(200); } // Boolean — auto-subtract on mix selObjs = [...objs]; await doCSG('union');
// NassScript

JS console —
full internal access

NassScript exposes every NASSCAD function directly. Native async/await lets you script time-sequenced operations — create parts, apply booleans, animate the camera — all in one pass.

  • Access all internal functions from the console
  • Native async/await for time-sequenced operations
  • History of the 20 last runs
  • Ctrl+Enter to execute instantly
  • Chain booleans, animate, procedurally generate
Read the docs →
// In Action

Real parts.
Real complexity.

Real STEP AP242 assemblies, imported straight into a browser tab — thousands of solids, source colors, full assembly tree.

NASSCAD — cruise ship STEP assembly: 2,813 solids imported in 48 seconds
STEP import · Cruise ship assembly · 2,813 solids · 773,669 faces · 48 s
NASSCAD — Scania 8x4 STEP assembly imported in the browser: 1,449 solids, 2.8M faces, 1.9M vertices
STEP import · Scania 8x4 · 1,449 solids · 2,847,613 faces · 2 min 23 s
NASSCAD — Scania V8 XT Turbo STEP import: 1,295 solids, 2.8M faces, source colors preserved
STEP import · Scania V8 XT Turbo · 1,295 solids · source colors preserved · 2 min 6 s
NASSCAD — architectural STEP model: 161 solids, full assembly tree in the browser
STEP import · Architectural model · 161 solids · full assembly tree · 13 s
// Model credits

The assemblies above are third-party CAD models, shown to demonstrate STEP import — they are not NASSCAD content and remain the property of their authors:

Modern Cruise Ship Evita and Rocky House by Christian Spreafico · Scania R620 V8 8x4 and Scania V8 XT Turbo Engine by Ivo Jardim.

All four are published on the GrabCAD Community Library and redistributed as STEP test data by STEP Tools, Inc. No model file is bundled with NASSCAD or hosted on this site.

// Companion engine · Windows x64

The CSG kernel
left the browser.

Import, inspect, measure and export STEP AP242 with nothing installed — all of that runs in your browser. Boolean operations are different: since V4.7.0 they run on MEDUSA, a companion engine written in native C++ with Manifold and Intel TBB, instead of single-threaded WebAssembly. Start it once and NASSCAD detects it on its own.

⬇ Download MEDUSA 3.1 — Windows x64 · 20 MB
1

Download and unzip — anywhere you like.
Everything is included, nothing else to install.

2

Run the engine — Nasscad_Medusa_Engine_3.1.exe.
It is not code-signed: SmartScreen shows a warning,
click More info → Run anyway.

3

Open NASSCAD — from this site or your own copy.
The CSG panel then reads
ENGINE: MANIFOLD C++ · MEDUSA
and boolean operations become available.

// Export & Import

From browser to
slicer, CNC or cloud

Eight export formats. Six import formats. Dimensions guaranteed 1:1. Section cuts for laser and CNC direct from the viewport.

.STL

Binary — Cura, PrusaSlicer,
Bambu, Simplify3D

.STL

ASCII — Human-readable,
text-based format

.OBJ

Wavefront — Blender,
MeshLab, most 3D tools

.3MF

3MF — Bambu Studio,
PrusaSlicer, full metadata

.GLB

Binary GLTF 2.0 — Sketchfab,
Blender, AR/VR, web 3D

.PLY

Stanford PLY — MeshLab,
CloudCompare, scan tools

✂ Section

SVG + DXF — 2D cut at any Y plane.
Laser cutters, CNC, LibreCAD

.STEP

AP242 Exact Analytical B-Rep — FreeCAD, Fusion 360,
Autodesk Viewer
OpenCASCADE OCCT WASM kernel

No account. No subscription. No cloud.

Just a file that runs in your browser and exports parts straight to your printer or CNC.
The tool gets out of the way. You build.

NASSCAD — Free Browser-Based Parametric 3D CAD, No Login Required

NASSCAD is a fully parametric 3D CAD application delivered as a single HTML file. It runs entirely in your browser via WebGL and WebAssembly — no server, no account, no installation. Open the page, model your part, export to your slicer.

The Best Free Alternative to Tinkercad, Fusion 360 and Onshape

Looking for a free alternative to Tinkercad that doesn't require a login? NASSCAD works anonymously, offline, and with zero cloud dependency — the ideal tinkercad alternative for 3D printing makers who value speed and privacy. Unlike Fusion 360, there is no subscription, no forced cloud save, and no 10-active-document limit. Unlike Onshape, your data never leaves your machine. It is also the best lightweight Fusion 360 alternative and a genuine browser-based CAD like Onshape — without the cloud lock-in.

Offline-Ready, Client-Side CAD — No Registration Needed

NASSCAD is a true offline browser-based CAD tool and a private cloudless CAD tool. Download the offline package for Windows — the application, the OpenCASCADE kernel and the MEDUSA engine in one archive. Unzip it, run it, and it works with no internet connection at all. It is a free online CAD without registration and an anonymous 3D modeling tool: every computation runs on your own machine, with a 2 GB GeometryPool, BVH raycasting, and IDB-backed undo. A zero setup 3D design app and a single file HTML 3D editor — auditable, open, and fast.

AIO HTML Package — Single-File Offline Build

The AIO (All-In-One) package bundles everything NASSCAD needs — the single-file application, Three.js, the full OpenCASCADE WASM kernel, fonts, every generator, the complete import/export pipeline and the native MEDUSA engine — into one archive. Download it, unzip it anywhere and run nasscad.bat: it starts the engine and opens NASSCAD in your browser. It works completely offline from then on, and needs no installer, no Node.js and no Electron runtime. It runs best in Chrome, which gives full WebAssembly and SharedArrayBuffer support for the 2 GB GeometryPool — Firefox and Safari work too, with reduced large-model performance. Ideal for USB sticks, locked-down machines, or anyone who wants the exact application pinned to a specific version.

MEDUSA — Native C++ CSG Companion Engine

MEDUSA is the native boolean engine behind NASSCAD, a C++ companion built on Manifold, OpenCASCADE and Intel TBB. It runs as a local server on 127.0.0.1 and NASSCAD detects it automatically — no account, no telemetry, nothing leaves the machine. Since V4.7.0, boolean CSG runs on MEDUSA instead of single-threaded WebAssembly, which is what makes multi-threaded native CSG possible from a browser tab. It ships as a portable folder with no installer and no runtime to add: unzip and run. Windows x64 today; macOS and Linux builds are planned.

Boolean CSG, Parametric Generators, Full Export Pipeline

Free Online STL Viewer — Inspect 3D Files in Your Browser

NASSCAD doubles as a fast, free online STL viewer. Drag and drop any .STL file — binary or ASCII — and inspect it instantly in a WebGL 3D viewport with orbit, pan and zoom. X-Ray wireframe mode reveals internal geometry, live dimension annotations show accurate part measurements, and the object properties panel reports vertex count, face count and bounding box. No upload to any server: the file stays in your browser tab. Ideal for checking a print file before slicing, validating a mesh from a colleague, or quickly reviewing a download before using it in another tool. Works with STL, OBJ, 3MF, GLB and PLY. And once your file is open you are already inside a full parametric CAD: add primitives, cut with boolean CSG, measure, and export the result as analytical STEP AP242 — same page, still nothing installed.

Free Online 3D Modeler — Design for 3D Printing in the Browser

NASSCAD is a free online 3D modeler built for makers and engineers. Design parametric parts from scratch using 18 watertight primitives — cubes, cylinders, spheres, cones, tubes, gears, screws, nuts and more. Combine them with boolean CSG operations powered by the native Manifold C++ kernel. Export directly to .STL for Cura, PrusaSlicer or Bambu Studio. No download, no install, no subscription — just open the page and start modeling. The same tool runs offline too: save the single HTML file to your desktop and use it with no internet connection.

Visual OpenSCAD Alternative with GUI

NASSCAD is the OpenSCAD alternative with GUI and a visual OpenSCAD modeler that bridges the gap between code-first tools and point-and-click modelers. NassScript exposes every internal function via an async/await JS console — no separate IDE, no compile step.

Technical Architecture — Fast Client-Side CAD Engine

Built on Three.js r128, OpenCASCADE OCCT WASM and Manifold (Apache 2.0, Google). Worker Pool ×4/×6/×8, GeometryPool 2 GB with mark-and-sweep GC, BVH/AABB caching, IndexedDB undo/redo (200 levels). Native multi-threaded CSG at full speed inside a lightweight WebGL 3D modeler. IndexedDB local 3D CAD logs. 18 watertight primitives. No external dependencies at runtime.

Also a free SelfCAD alternative, a SketchUp web alternative free, and a client-side 3D CAD software that respects user privacy. CC BY-NC 4.0 — NassLab, Nasser, France, 2026.

The code is open and readable. What can't be copied is the vision behind it.

NassLab has several ambitious projects in the pipeline — electronics, advanced WASM engines, aeronautics and more. NASSCAD is just the beginning.

NASSCAD Online is the free, single-file HTML edition. A native C++/Qt engine — same philosophy, same primitives, built for raw performance — is already in development.