AutoCAD 2018 – why did the DWG format change?

In my review of AutoCAD 2018, I had this to say about AutoCAD 2018’s changed DWG format:

Why does AutoCAD 2018 need a new DWG format? It probably doesn’t. The 2013 DWG format is capable of holding pretty much anything you want… Although Autodesk cites performance reasons with certain drawings, I strongly suspect the new DWG format was introduced purely to make life difficult for competitors, and to encourage wavering customers to stay with Autodesk for fear of losing compatibility. In other words, it seems likely this is an anti-competitive change rather than a technical one.

In a recent blog post, highly respected Swiss-based Autodesk development and research person Kean Walmsley had this to say on that subject:

The main reason for the break in compatibility is some longer-term work that’s going on inside the AutoCAD codebase. For now this is really only surfacing …

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The biggest DWG file I’ve ever seen

Today, I tried to investigate a DWG file that one of my users couldn’t open. It wouldn’t open for me on an old 1 GB PC. Trying a PC with 4 GB didn’t help, and neither did experimenting with various releases of AutoCAD. Depending on the release, AutoCAD would either try to open the drawing and eventually die with an out of memory error, or would instantly inform me that the drawing was too big to open. I don’t have access to a 64-bit version of AutoCAD (which might possibly be able to open this monster on a PC with more than 4 GB of RAM), so the drawing is effectively useless.

The drawing is 242 MB (254,145,119 bytes), which I’m pretty sure is the largest drawing I’ve ever encountered. Based on a plot of a previous revision of the the drawing, it should be about 200 to 300 KB, …

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