Cadenza

Oct 14, 2026

Cadenza (a CAD engine with a za) opens DWG and DXF drawings on a Mac, an iPhone or an iPad. You double-click the file and it is there, with its layers, its fonts and its blocks, drawn on Apple’s very well-marketed GPU and quick to pan around.

In MEP work the drawings arrive as DWG. The architect sends one, the engineer sends another, and I have to boot a Windows VM to look at them properly before making an offer. On a Mac the choices are a slow AutoCAD subscription for a file you only want to look at, a Windows machine, or a web viewer that wants the 100 MB drawing uploaded first. None of them is a double-click.

So I wrote one. It was supposed to be a viewer and nothing more. But constraints laugh at you when you set them, don’t they?

The apartment plan from CADCraft's examples, open in Cadenza on the Mac.

Reading the file

DWG is Autodesk’s own format, and the usual way to read it is someone else’s library. There is also a published specification, written, I suspect, on the assumption that nobody would read it. Claude did, so Cadenza doesn’t borrow anyone’s library. The decoder is pure Swift, written from the Open Design Alliance’s specification and checked against every other reader I could get my hands on. DXF, the text cousin, has its own parser next to it. There are no third-party libraries anywhere in the app.

It reads AutoCAD files from R13 up to 2018, which covers what people actually send around. Text is drawn with AutoCAD’s own SHX fonts and falls back to system fonts per character, so Greek annotations come out as Greek and not as question marks. External references load beside the drawing, faded, as you would expect.

The same drawings on the iPhone: tap a line for its properties, or search the text, Greek included.

Searching a drawing for “pvc” and stepping through the hits.

On the Mac it also puts previews and thumbnails in Finder through Quick Look, so you can press Space on a DWG and see what it is before opening anything. STEP files from the mechanical people open too, shaded in 3D with an orbit camera — just because I can.

Then it started editing

Then I saw the open-source CADCraft, and it clicked that a viewer is only a few verbs away from an editor. I think Cadenza does better on many fronts. They will overtake me eventually, but mine only has to be good for my own uses.

Version 1.4 edits drawings on the Mac. The usual AutoCAD verbs are there (move, rotate, trim, extend, fillet, offset and friends), typed at a command line the way your fingers already know. There is also a cadenza CLI, as CADCraft has, so my agents can draw too.

Here is how an editing and measurement workflow runs.

The part I care about most is saving. Cadenza doesn’t rewrite your file; it patches it. Everything you didn’t touch is copied byte for byte, and only what you changed is written again. An edit that can’t be saved exactly is refused rather than quietly simplified. When you send a drawing back to the architect, it should be their drawing with your change in it, not a lossy translation of it.

DXF saves as DXF, and DWG saves as DWG for AutoCAD 2004, 2010, 2013 and 2018 files.

Select something and you get its grips and properties, as you would in AutoCAD.

A real electrical drawing: moving symbols, stretching with grips, then measuring distances and areas.

The limits

Paper-space layouts aren’t shown yet; Cadenza draws model space. But you can print and export. Editing is Mac-only, and AutoCAD 2000 and 2007 files open but can’t be saved. Some diagonal hatch patterns come out with the wrong spacing. Quick Look shows a drawing without its external references, because it only gets the one file.

It needs macOS 26 or later.

Getting it

There is no public download yet. If you want to try it, email me and I will send you the .dmg. Open it and drag Cadenza to Applications.