File Format FCStd/cs

Overview
The FreeCAD Standard file format is FreeCAD's main file format. It is a compound format, supports compression and embedding of different kinds of data.

Internals of .FCStd files
FCStd is a standard zip file containing one or more files in a specific structure. As such, it is possible to unpack a file using a regular zip decompression tool, but care needs to be taken while packing the contents of a  file. FreeCAD contains a "Project Utility" to re-pack files, it's use is described in Change the source of the file .FCStd below.

Document.xml
This is the main file describing all the objects inside a FreeCAD document, that is, only the geometric and parametric definition of the objects, not their visual representation. If FreeCAD is ran in console mode (without the GUI), only this will be used.

GuiDocument.xml
This is the GUI counterpart of the file. For each object described in the, there is one corresponding object in , describing the visual representation of that object (color, linewidth, etc).

Thumbnails/thumbnail.png
This is a 128x128 pixels thumbnail image of the document, which is a screenshot of the 3D view at save time. Thumbnails are generated only if the corresponding option is enabled in the FreeCAD preferences.

Templates/*.svg
In the Templates folder are stored the template svg files used in Drawing pages.

*.brep
These are the B-rep shapes of all objects that have a Part shape in the. Each object, even if it is parametric, has its shape stored as an individual file, so it can be accessed by components without the need to recalculate the shape.

Typical structure
Structure of a typical file. The extension can be changed to to explore it like a normal directory. The and  are at the root of the archive, together with any number of  (BREP) files. One subdirectory may hold the thumbnail, and another the SVG templates used by TechDraw.

File.FCStd (File.zip) | :--thumbnails/ |    :--Thumbnail.png | :--Templates/ |    :--MyPage.svg | :--Document.xml :--GuiDocument.xml :--Shape1.brp :--Shape2.brp :--etc.

Change the source of the file .FCStd

 * See Std ProjectUtil.

Other

 * A file Converter utility ImageConv.