About CADverter

Who builds it

One independent developer, who also builds the other tools in the small network reachable from the All tools button: a Windows crash-dump reader, a Parquet and CSV workbench, and a peer-to-peer file transfer page. All four share the same principle — the file you drop is processed on your device and nowhere else — and the same tip-jar model. There is no company behind them, no investor and no growth team; the site exists because its author needed it and assumed others would too.

How a CAD kernel runs in a browser tab

The geometry kernel is OpenCASCADE Technology, the same open-source B-rep kernel behind FreeCAD, compiled to WebAssembly (the opencascade.js build, version 1.1.1). It is a 63 MB binary, served brotli-compressed at about 10 MB, fetched the first time a CAD operation is needed and then cached in the browser’s IndexedDB, so the second visit is instant. Meshes in the many game and DCC formats are read by Assimp, also compiled to WebAssembly (about 4 MB). Rendering is three.js on WebGL. Both engines run in Web Workers, so a long conversion never freezes the page, and a runaway one can be cancelled by terminating its worker.

Everything that is not one of those two engines is written in TypeScript for this site: the format registry that every claim on every page is checked against, the STEP writer that builds a solid directly from a mesh’s topology in seconds where kernel sewing took half an hour, the 2D drawing model and its DXF, SVG, PDF, EPS and HP-GL readers and writers, the G-code interpreter and cut simulator, the profile analysis that explains why an outline will not close, and the drawing-sheet layout with its dimensioning. The site is a single static bundle served from a shared cPanel host; there is no application server at all.

How the no-upload claim is tested, not just stated

Two mechanisms. First, the page ships a strict Content-Security-Policy — connect-src 'self' and no third-party origins at all — so even a bug could not send data anywhere but back to this site’s own static files. Second, the end-to-end test suite runs against the production build, opens a model, converts it and downloads the result while recording every network request, and asserts that the list of requests to any external origin is empty. A separate suite serves the built site with the exact production headers and exercises each engine under that policy, because a worker takes its policy from its own response and the ordinary test runs would otherwise miss a violation.

You can repeat the check yourself: open the browser’s developer tools on the Network panel, drop a file, convert, download, and read the request list. Beyond this page’s own assets there is nothing.

What it cannot do, stated plainly

It cannot open native proprietary CAD files — SolidWorks .sldprt, Inventor .ipt, CATIA .CATPart, Creo and NX .prt — because no reader exists that can be shipped in a browser; the guides on this site show how to export STEP from each. It cannot open DWG, for the same licensing reason; save as DXF first. Converting a mesh to STEP produces a faceted solid, not smooth surfaces, unless the optional reconstruction recovers the analytic faces a CAD-derived mesh came from; fillets are its weak spot. The size ceiling is your machine’s memory, because the whole model lives in the tab: ordinary parts and modest assemblies open comfortably, very large assemblies may not. PDF conversion reads vector paths only — no text outlining, no scans, first page only. Each convert panel lists what the chosen target format will lose before you download.

How correctness is kept

The format registry is the single source of truth for what is readable, writable and preserved; the landing copy, the convert panel, the warnings and the generated pages are all derived from or tested against it, so a claim cannot outrun the code without a test failing. Writers are verified by round trip — the output is read back through the real engine and compared — including the STEP writer’s assembly and colour entities, which are checked through OpenCASCADE’s own XCAF reader rather than by searching the file for entity names. The unit suite runs on every deploy; the browser suites run before a release.

Why it is free, and how it stays that way

There is no server doing work per user, so there is no per-user cost to recover: hosting a static bundle costs a few dollars a month regardless of how many files are converted. The tip jar (Bitcoin, Ethereum, Solana; QR codes generated in the page) covers that and the developer’s coffee. Nothing is tracked — no analytics script, no cookie, no fingerprinting — because there is nothing to sell and no one to sell it to.

What has changed recently

Recent additions, newest first: dedicated pages for the most-requested conversions and export guides for SolidWorks, Inventor and CATIA (September 2026); a dark default theme and a slicer-3MF reader that opens a sliced plate as the program it carries (August 2026); G-code reading as the machine that wrote it, with lathe and plasma modes; a 2D drawing generator with dimensions, sheet sizes and first- or third-angle projection; per-part selection and per-part export; surface reconstruction for CAD-derived meshes; the JavaScript STEP writer that made mesh-to-STEP a seconds-long operation. The site launched on 3 August 2026.

Credits and licences

OpenCASCADE Technology (LGPL-2.1 with exception), Assimp (BSD-3), three.js (MIT), all self-hosted rather than loaded from a CDN. The sample model is #3DBenchy by Creative Tools, redistributed unmodified under CC BY-ND 4.0. CADverter is not affiliated with Dassault Systèmes, Autodesk, Siemens, PTC or the Open Design Alliance; product names appear only to describe file-format compatibility.

Questions about the site