This article will show you how to find out exactly which layer is causing your FreeCAD file to balloon in size, by getting a granular list of all of the layers in your document tree, sorted by size.

Context

Recently, we had a volunteer who made some very helpful contributions to the Eco-Libre Life-Line project — an open-source design for raw water intake, filtration, and storage system for sustainable communities.

The original file was 812 KB. After the changes, the file was 17 MB (compressed). And — worse — manipulating the objects in FreeCAD was now very slow and choppy (spoiler: the uncompressed size was 114 MB).

Before merging the updated objects into our GitHub, I figured that some optimizations could be made to reduce the file size — to make opening the file in FreeCAD much smoother. But which object should I focus on optimizing?

Sorting layers by size

You can see the size of each layer by pasting a small python snippet into FreeCAD’s python console.