ZSTD (.zst)

Import and Export fully support the Zstandard file format.

Background & Context

- MIME type: application/zstdZstandard (zstd) compression method and file format.
- General-purpose lossless compression method.
- Commonly used for archiving data and for exchanging files on the internet.
- Developed by Yann Collet at Facebook in 2015.
- Binary format.
- Stores a single file.

Import & Export

Import["file.zst"] uncompresses file.zst and imports file, automatically inferring the format from the file contents.
Import["file.ext.zst",elem] imports the specified element from the uncompressed file "file.zst".
Import["file.ext.zst","format"] uncompresses a GZIP file and imports "file.zst" as "format".
Import["file.ext.zst",{"format",elements}] imports elements from "file.zst" as "format".
Import["file.ext.zst",{elem,sub_a,sub_b,…}] imports a subelement.
The import format can be explicitly specified with Import["file.zst",{"Zstandard",…}].
Export["file.ext.zst",expr] exports any expression expr to a Zstandard-compressed file whose format is implied by the file name extension .ext.
The export format and Zstandard compression method can be explicitly specified with Export["file",expr,{"Zstandard","format"}].
See the following reference pages for full general information:

	Import, Export	import from or export to a file
	CloudImport, CloudExport	import from or export to a cloud object
	ImportString, ExportString	import from or export to a string
	ImportByteArray, ExportByteArray	import from or export to a byte array

Import Elements

The Zstandard format itself does not support Import or Export elements.
Import elements of the Zstandard-compressed file:

	"Elements"	list of elements and options available in this file
	"Summary"	summary of the file
	"Rules"	list of rules for all available elements
	"Options"	rules for options, properties and settings

Import["file.ext.zst","Elements"] returns the names of elements available in file.ext, effectively unpacking the compressed file before importing "file.ext".

Options

General Export option:
CompressionLevel Automatic Zstandard compression strength, given as a number in the range 0 to 1
The setting CompressionLevel->1 corresponds to the strongest available compression, resulting in the smallest possible file size.

Examples

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Basic Examples (2)

Export a string to a ZSTD-compressed text file:

Convert the previous output back to a Wolfram Language string:

This exports graphics to a ZSTD-compressed JPEG file:

This gives the available Import elements of the JPEG file:

When importing any element from a .zst file, the Wolfram Language automatically uncompresses it:

Export Options (2)

CompressionLevel (2)

By default, the maximum amount of compression is used:

This is equivalent to CompressionLevel1:

Specify the minimum amount of compression:

Plot file size over increasing compression level:

Properties & Relations (2)

Get some text to export:

Compare GZIP, BZIP2 and ZSTD compression to the uncompressed size:

Compare GZIP, BZIP2 and ZSTD compression speeds:

The amount of compression depends on the data being compressed. For example, JPEG images are already compressed and cannot be compressed any further by GZIP:

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