SKP model.dat and meta.dat (SketchUp 2021 and later)

Two members of the archive, meta/meta.dat and model.dat, are trees of tagged values. meta.dat is small and its tags are listed below. model.dat holds the whole model and only its first levels have been examined. All numbers are little-endian.

Elements

Both files are made of elements, each a tag, a length and a value:

Offset	Size	Type	Name	Meaning
0	2	u16	Tag	What the element is.
2	4	u32	Length	The length of the value in bytes.
6	length	bytes	Value	Either a value (a number, ASCII text, a GUID) or further elements.

The element does not say whether its value is plain data or more elements; that depends on the tag. OpenSKP keeps a list of the tags that hold elements, and for meta.dat the explorer does the same, with the tags 0x0064, 0x0067, 0x0068, 0x0078, 0x00C8, 0x00C9, 0x00CA and 0x2328.

To read a tree: read the tag (u16) and the length (u32); if the tag is one that holds elements, read elements from the value until its end, which they must fill exactly; otherwise take the value as it is. Then go on with the next element after the value. Numbers in values are little-endian, and text is ASCII without a terminating zero.

meta.dat

meta/meta.dat is 330 to 595 bytes once inflated in the files seen. It is one element, tag 0x0064, holding all the others.

00000000  64 00 44 01 00 00 75 00 08 00 00 00 32 33 2E 31
00000010  2E 33 34 30 76 00 02 00 00 00 17 00

The start of a meta.dat: element 0x0064 of 324 bytes; inside it 0x0075 holds “23.1.340” and 0x0076 holds 23

The tags seen, and what they hold in the files examined:

Tag	Holds	Meaning
`0x0064`	elements	Everything.
`0x0075`	ASCII	The version, such as `23.1.340`.
`0x0076`	u16	22 or 23: probably the major version.
`0x0077`	u16	0 in a 22.0 file, 2 in 23.1 files. Not known.
`0x0073`	u16	1. Not known.
`0x0074`	u16	13. Not known; the VFF bytes also hold a 13.
`0x0066`	16 bytes	A GUID.
`0x0067`	elements	The model thumbnail: a `0x2328` element.
`0x0068`	elements	The preview picture: a `0x2328` element.
`0x2328`	elements	An image: `0x2329` and `0x232A`.
`0x2329`	u32	The image type: 4, as the older files’ 4 for a PNG.
`0x232A`	ASCII	The member name, such as `meta/model_thumbnail.png`.
`0x0069`	1 byte	1. Not known.
`0x006A`, `0x006B`, `0x006C`, `0x006E`, `0x006F`	empty	Not known.
`0x006D`	ASCII	The units, such as `Meter` or `Inches`.
`0x0070`	1 byte	1. Not known.
`0x0071`, `0x0072`, `0x0079`	1 byte	0. Not known.
`0x0078`	elements	The save history: `0x00C8`, holding `0x00C9`, holding the saves.
`0x00C8`, `0x00C9`	elements	The levels of the save history.
`0x00CA`	elements	One save: `0x00CB` and `0x00CC`.
`0x00CB`	ASCII	The program and its version, such as `SketchUp Client (Windows) 23.1.340` or `SketchUp Client (Mac) 22.0.353`.
`0x00CC`	u32	The time of the save, a Unix time.

The save history

Every save of the model adds a 0x00CA element. One 2022 file’s history reads:

#	Saved by
1	21.0.332, Windows (17 September 2020)
2	21.0.312, Mac
3	22.0.101, Mac
4	22.0.353, Mac
5	22.0.403, Windows
6	22.0.353, Mac

The file’s version string says {22.0.353}, the last save. So a file saved by 22.0.403 was saved again by the older 22.0.353: the format is versionless in practice. The explorer shows the history as a table.

model.dat

model.dat was 17.5 MB to 86.6 MB once inflated in the files seen (3.8 MB to 21.9 MB stored). The whole member is one element, tag 0x01F4, whose value is a run of elements that fill it exactly: 26 of them in a 2023 file. Its first children:

Tag	Holds
`0x0063`	A u32, 0.
`0x020A`	The text `meta/meta.dat`.
`0x0209`	Dynamic property dictionaries: `0x36B1` → `0x36B2` → `0x36B3` → `0x36B4` with a name such as `ModelProperties`, keys in `0x36B6` such as `Description`, `IsClassified`, `IsDynamic`, `IsLive` and `Name`, and typed values: the type in `0x38A4`, then `0x38AA` a true or false, `0x38A7` an integer, `0x38A9` an f64 or `0x38AD` a string.
`0x0200`	The option groups: names in `0x61AB` (`UnitsOptions`, `PageOptions`, `SlideshowOptions`, `NamedOptions`, `PrintOptions`) and keys in `0x61AD` with typed values, the same groups and keys as the options of the older files.
`0x01F5`	Not examined.
`0x01FA`	Not examined.

00000000  F4 01 xx xx xx xx 63 00 04 00 00 00 00 00 00 00

The start of model.dat: the outer element 0x01F4 and its length (xx), then 0x0063 holding a u32 0

Beyond these, nothing in model.dat was checked for this site.

OpenSKP’s reading of the geometry

OpenSKP’s binary format notes list the tags it reads for the geometry. They are its reading, not checked here. The notes write tags as their two bytes in file order, so their C409 is the tag 0x09C4.

Tag	OpenSKP’s reading
`0x09C4`	A vertex, with its coordinates in `0x09C5` as three f64s.
`0x0BB8`	An edge.
`0x0DAC`	A face.
`0x157C`	A component definition, with its GUID in `0x157D` and its name in `0x157E`.
`0x1964`	A component instance, with its transform in `0x1966` as 13 f64s.
`0x3C8D`	A layer (tag) name.

OpenSKP gives the coordinates in inches, with Z up.

The explorer’s outline

The explorer inflates up to the first 64 MB of model.dat and lists the top element and two levels below it, with each element’s offset, tag and length. It reads a value as elements only where they fill it exactly, and otherwise shows the value as bytes or text. That a value which divides exactly into elements is elements is an inference, and the outline says so.