.SKP File Format

SketchUp 2021 and later model

Introduction

These are the models saved by Trimble’s SketchUp 2021 and every release since. SketchUp 2021 came out in November 2020, and its release notes, as quoted on SketchUp’s forum, announced “a re-build of the .SKP file format”, with “a significant reduction in file sizes”. SketchUp staff wrote on the forum that the format was reworked “to allow for forward compatibility”.

The SketchUp C API calls this the “versionless” file format. Its list of file versions ends with SUModelVersion_SU2021, and its note says that from SketchUp 2021 SketchUp uses the same file format across versions, so that SketchUp 2021 can open a file made in SketchUp 2022. So every release from 2021 on writes this one format: later versions add to it, and earlier ones still open the result. A file can even be saved by one release and then again by an older one, as the save history inside the files shows.

The file keeps the two strings that every SKP file starts with, then becomes a ZIP archive. The thumbnails are PNG files, the materials and styles XML documents, and the model itself a tree of tagged values in a member called model.dat. The files examined for this site were saved by SketchUp 2022 (22.0.353) and 2023 (23.1.340); none from 2021, 2024, 2025 or 2026 was examined.

A file dropped on any page of this site opens in the explorer, which shows the thumbnail and the preview picture, the save history, every member of the archive, the materials with their colours and textures, and an outline of model.dat.

Structure

All numbers are little-endian.

  1. 0Signature the CString “SketchUp Model”32 bytes
  2. 32Version the CString “{23.1.340}”: the SketchUp that saved the filevaries
  3. 56VFF header “VFF” and four numbers13 bytes
  4. 69ZIP archive to the end of the file; its offsets count from hereto the end
    1. …meta/model_thumbnail.png, meta/preview_thumbnail.png two picturesPNG
    2. …meta/meta.dat version, units and save historytagged values
    3. …materials/ one folder a material, with its texturesXML
    4. …thumbnails/ component thumbnailsPNG
    5. …styles/ the stylesXML
    6. …model.dat the modeltagged values
    7. …Central directory one record a membervaries
    8. …End record22 bytes
The parts of a SketchUp 2021 and later file, with the members in the order seen; the offsets are those of a ten-character version string

The archive is an ordinary ZIP with two particulars: its offsets count from the start of the archive, not of the file, and every member is compressed with Deflate, the PNGs as stored blocks so their bytes sit in the file as they are. See ZIP archive. The tagged-value trees of meta.dat and model.dat are on model.dat and meta.dat; beyond the first levels, model.dat is not decoded here.

Telling it apart

The explorer’s parser for this format checks, in order:

  • the 32 bytes of “SketchUp Model” at the start, which every SKP file has;
  • a version string in braces, such as {23.1.340};
  • the letters VFF straight after it;
  • a ZIP local header, PK 03 04, 13 bytes after the start of VFF;
  • a ZIP end record whose central directory is where it says, counting from the start of the archive (or, for other writers, from the start of the file).

A file that fails a check is turned down, and the explorer tries the parsers for the other SKP formats. Older SketchUp files go on after the version with a GUID and an MFC archive instead. A version below 21 with this layout is accepted but reported.

Variants

Links

Software

  • SketchUp – Trimble’s 3D modelling program, which saves these files from version 2021 on (Windows, macOS, web, iPad)

Developers

  • SketchUp SDK – Trimble’s library for reading and writing SKP files (C)
  • OpenSKP – reverse-engineered reader and writer, which calls this the VFF format of SketchUp 2021 and later (Python, C#, TypeScript, Dart)
  • skppy – reader and writer for both containers, with a Blender add-on; in beta (Python)

Reference