What is the SKB file format?
The .skb format stores an automatic backup copy of a 3D model created in SketchUp, the 3D modelling application now developed by Trimble (originally @Last Software, later briefly owned by Google). It contains a carbon copy of the model data held in the corresponding .skp file - the two are byte-for-byte identical, differing only in extension.
A .skb file is automatically generated by SketchUp when the auto-save function is enabled. It serves as a backup copy in case the original file becomes corrupted or accidentally deleted. The backup is always saved in the same folder as the main file containing the 3D model data.
Both Windows and macOS are supported, as SketchUp was designed from the ground up with those operating systems in mind. On Windows the backup appears as filename.skb; on macOS it is saved as filename~.skb.
To open a .skb file, rename it to .skp and open it in SketchUp as normal - no separate conversion step is needed because the internal structure is unchanged.
Security & safety
RISK: LOWAn .skb is a data file (a SketchUp model), not a program, so opening one is generally safe. As with any .skp, SketchUp models can carry extensions/dynamic-component scripts and complex parsers have occasional vulnerabilities - keep SketchUp updated and only open files from sources you trust. Practical caution: when recovering, ALWAYS work on a COPY of the .skb and keep the original untouched, so a botched rename or save doesn't destroy your only backup. Don't delete .skb files unless you're sure the matching .skp is intact.
Format details
in a nutshellPrograms that open SKB files
Windows3 apps
SketchUp (rename to .skp)
Paid Copy the .skb, rename the copy 'file.skb' -> 'file.skp', then File -> Open it in SketchUp. Save As a new name once it opens.
SketchUp Free (web)
Freemium Rename .skb -> .skp, then upload it in the browser app - opens with no install and stays on the latest version (fixes 'too new' errors). 
macOS2 apps
SketchUp (rename to .skp)
Paid Duplicate the .skb, change the extension to .skp, then File -> Open in SketchUp; Save As a fresh file.
SketchUp Free (web)
Freemium Rename .skb -> .skp and upload in the browser - works on Mac with no install. Technical details
deep spec| File classification | Automatic backup snapshot of a SketchUp model; byte-for-byte clone of the .skp primary file |
| Internal binary format | Proprietary SketchUp binary (same structure as .skp); recent versions store model data inside a ZIP container |
| MIME type | application/octet-stream |
| File header | Version-dependent; recent files begin FF FE FF 0E followed by the UTF-16LE string "SketchUp Model" |
| Compression | Recent SketchUp versions wrap model components in a ZIP archive internally; older versions use uncompressed proprietary binary blocks |
| Encoding | Binary (proprietary, not a text or XML format) |
| Recovery procedure | Rename .skb to .skp and open directly in SketchUp - no conversion or special tool required |
| Auto-save behavior | Created or overwritten automatically each time SketchUp saves; only one .skb backup exists per model file at any time |
| Storage location | Placed in the same directory as the source .skp file |
| Windows filename pattern | filename.skb (mirrors the .skp name with extension changed) |
| macOS filename pattern | filename~.skb (tilde inserted before the extension) |
| Version compatibility | Version number stored internally; a backup from a newer SketchUp release may not open in an older version of the application |
| Developer / owner | Trimble Inc. (format originated at @Last Software; owned briefly by Google 2006-2012) |
| Related primary format | .skp - the live SketchUp model file that .skb backs up |
| Released | Backup feature of SketchUp (since the early SketchUp releases, 2000s) |
| Specification | help.sketchup.com |
SKB conversions
Community Q&A
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