Saved files

Save in the top bar downloads sketch.slop.json. Open reads one back.

The file is text, so it survives version control and diffs sensibly, and it is the only way to move an editable part between sessions or machines.

What it holds

Every sketch	Points, lines, circles, arcs, and their identifiers
Every constraint	Including dimension values
The document order	Which sketch is a base sketch and which sits on a face
Face references	Which face of which earlier feature a sketch was drawn on
Extrudes	Distance, add or cut, midplane
Blends	Kind, size, how far each reaches, and the far-end size if it tapers
Projected reference geometry	Which sketches had their parent projected
Traced references	What each sketch traced off the solid, as the thing it was traced from
Part colours	The swatch colour of each feature
Dimension placements	Where you dragged each annotation on the canvas
Body names and combines	What each solid is called and the booleans between them
Body groups	How the bodies list is folded up, and what each group is called
Joints	Which face of which body holds which, and the offset and angle on each
Imported solids	The whole STEP file, not a path to it
Parameters	The named-value table, as names and expressions, with each row's Configure-panel face when it has one
Field expressions	What drives each driven dimension, extrude and blend
Kept measurements	The two things each was taken between, not the number it read

Reopening a saved document reproduces the part exactly, including the parametric behaviour: change a dimension and everything downstream still rebuilds.

An imported solid travels whole, on the same reasoning: the document rebuilds itself from what it carries, so it cannot depend on a file still being where it was. A document holding a large imported assembly is therefore a large document.

What it does not hold

The solid	Rebuilt from the features on open, never stored
Undo history	Every document opens with an empty history
The camera	The 3D view frames the model afresh
View preferences	Grid snap, panel widths and fold state belong to the browser, not the file
Which bodies are hidden	Every body comes back showing
Which groups are folded shut	The membership is saved; the folding is not
The rollback marker	A document opens built to the end of its timeline
Where jointed bodies stand	The joint is saved, not the position it worked out; see joints

Because the solid is rebuilt rather than stored, opening a heavy document takes as long as building it did. A part with several curved cuts can take noticeable seconds. See rebuilds and speed.

Older files

The format has gone through nineteen revisions, and every one still opens. A file saved by an older version is upgraded as it loads: missing fields take sensible defaults and face references are translated to the current scheme.

Saving always writes the newest revision, so opening and saving an old file upgrades it. There is no way to write an older revision.

When it will not open

A file that is not a valid document gives not a slop-cad document in the Selection section. The current document is left alone.

Keeping your work

Save writes the file, and that file is the copy that keeps. There is no document list and no revision history.

The browser holds the document you have open, in local storage, and offers it back the next time the app loads. It holds one, it holds it for this browser only, Clear drops it, and a document carrying a large imported file can be too big for it. Treat it as the net under a closed tab rather than as somewhere your work lives. See save, open and clear.

Exporting instead

To hand the part to a slicer or a renderer rather than back to this tool, use STL or OBJ. Those are meshes and cannot be opened back as an editable document.