SKB File Documentation

Summary

An SketchUp Backup Document is the automatic safety copy SketchUp keeps of a model, saved next to the working .skp with the same name. Its extension is .skb, and it is byte-for-byte a SketchUp model in the .skp format — only the extension differs. To open it, copy the file, rename the copy from .skb to .skp, and open it in SketchUp. It holds the previous saved state, so it is what you reach for when the main file is lost or corrupted.

Technical details

Feature	Value
Full name	SketchUp Backup Document
File extension	`.skb`
MIME type	`application/octet-stream`
Format type	Automatic backup — identical binary format to `.skp`
Category	Backup file
Created by	SketchUp (when “Create backup” is enabled)
Developer	Trimble Inc. (formerly @Last Software, then Google)
Introduced	Early SketchUp releases (2000s); SketchUp first shipped 2000
Contents	Previous saved state of the matching `.skp` model
Location	Same folder and base name as the `.skp`
Version-specific	Yes — a newer SketchUp’s backup will not open in an older one
Open standard	No — proprietary format
Signature (recent versions)	`FF FE FF 0E` + UTF-16LE “SketchUp Model” (version-dependent)
To open	Rename a copy to `.skp`, then open in SketchUp
Safe to delete	Yes, if the matching `.skp` opens correctly
Related extensions	`.skp`, `.layout`, `.stl`, `.dwg`, `.dae`

File signature (magic bytes)

FF FE FF 0E 53 00 6B 00 …

Offset 0. Because an .skb is a SketchUp model stored in the .skp format, it shares that format’s header rather than having one of its own. Recent versions begin FF FE FF 0E followed by the UTF-16LE (little-endian) text “SketchUp Model” — the 53 00 6B 00 above is S k in UTF-16LE. The exact bytes are version-dependent, so there is no single stable magic number; older files differ. Identify an .skb exactly as you would an .skp.

What is an SKB file?

An SKB file is SketchUp’s automatic backup. SketchUp is the 3D-modelling application first released in 2000 by @Last Software, acquired by Google in 2006 and owned by Trimble since 2012. When SketchUp’s “Create backup” option is enabled, every time you save a model it keeps the previous saved version as an .skb next to the current .skp, in the same folder and under the same base name. So if House.skp is your working file, House.skb is the save before it.

The key thing to understand is that an .skb is not a separate or reduced format. It is a complete SketchUp model stored in exactly the .skp binary format; the only difference is the three-letter extension. Everything a normal SketchUp file contains — geometry (edges and faces), components, materials, tags/layers and scenes — is present in the .skb. That single fact drives everything else on this page: to work with an .skb you treat it as a .skp.

Why SketchUp writes an .skb, and what it protects against

The whole purpose of the .skb is recovery. Each save cycle, SketchUp renames the model file that existed before the save to .skb, then writes the new .skp. The result is that you always have the current save and the one immediately before it. If the .skp becomes corrupted, refuses to open, or you accidentally wreck the model and save over it, the .skb still holds the previous good state. The trade-off is that the backup is exactly one save behind, so recovering from it may cost you your most recent edits — almost always a better outcome than an unreadable file.

Newer SketchUp versions also keep periodic auto-save copies, and on some setups a recovery file may appear in a SketchUp AutoSave location rather than as a sibling .skb. The .skb specifically is the “previous manual save” copy that lives beside your file.

Recovering a model: rename .skb to .skp

Opening an .skb is a rename, done carefully. The safe procedure:

1. Make a COPY of House.skb (keep the original untouched).
2. Rename the copy's extension:  House.skb  ->  House.skp
3. In SketchUp: File > Open the renamed .skp.
4. Immediately File > Save As under a new name (House_recovered.skp).

Working on a copy matters: if the rename or the save goes wrong, the original backup is still intact as your last line of defence. On Windows you may need to enable “File name extensions” in File Explorer’s View menu before you can change the extension; on macOS, renaming in Finder prompts you to confirm the change. Once the model opens, saving it under a fresh name gives you a clean working .skp again.

Why a renamed .skb still won’t open

The most common reason a correctly renamed .skb still fails is a version mismatch. Because the backup is a SketchUp model, it is version-specific just like .skp: a file written by a newer SketchUp release cannot be opened by an older one, which reports an “unsupported version” error. The fixes are the same as for any .skp. The simplest is to open the renamed file in SketchUp Free, the browser-based version, which stays current and therefore reads files that are “too new” for an older desktop install. Alternatively, someone with the newer SketchUp can re-save the model down to an older version. If you only need to look at the geometry, the free SketchUp Viewer opens a renamed .skp for orbiting and inspection without editing.

Getting other formats out of an .skb

All of the “convert my .skb” questions route through the same first step: recover it to a .skp, then export from SketchUp. Rename the copy to .skp, open it, and use File › Export. STL export (for 3D printing) is available in both SketchUp Free and Pro — make the model a solid group first. DWG and DXF export for CAD requires SketchUp Pro; the free web tier does not export them. A 2D graphic or PDF export produces a picture or drawing of the model, not its 3D data. There is no separate .skb converter, and there does not need to be: the file is already a SketchUp model.

Is an SKB file safe, and can I delete it?

An .skb is data, not a program, so opening one (after renaming) is generally safe. As with any SketchUp model, files can carry extension or dynamic-component scripts and complex parsers occasionally have vulnerabilities, so keep SketchUp updated and only open files you trust. The practical caution is about your own data: always recover from a copy and keep the original .skb untouched, so a botched rename or save does not destroy your only backup.

Deleting is straightforward. If the matching .skp opens correctly and you do not need the previous save, the .skb is safe to remove — it is only a safety copy. But if your .skp is damaged or missing, keep the .skb; it may be your only route back to the model.

References

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