Open ZST files on Mac
To open a Zstandard file on Mac, use Kernir or an installed zstd command to decompress it. Zstandard is often shortened to ZSTD, while .zst is a common filename extension. Kernir reads Zstandard-compressed data but does not write ZSTD output.
A stream or a TAR archive?
notes.txt.zst normally expands to one document. Project.tar.zst contains a TAR archive compressed with Zstandard, so the eventual result can be a tree of files. The compression name alone does not tell you which kind of data is inside.
The current Kernir reader recognizes both standalone Zstandard streams and TAR.ZST. Both are read-only formats in the app. TAR.ZST is not part of its writable TAR.GZ, TAR.BZ2 and TAR.XZ group; do not infer write support just because other compressed TAR formats are writable.
Use the command if installed
Check for a command-line installation in Terminal:
command -v zstd
If no path is returned, use a compatible application or obtain the tool through the Zstandard project. Do not assume every macOS version supplies this command or has the same Zstandard support in its archive utilities.
With the tool available, for a file in Downloads:
cd ~/Downloads
zstd -d -k "notes.txt.zst" -o "notes-expanded.txt"
Use your filename and an output name that does not already exist. -d requests decompression, -k retains the source, and -o names the result. Check completion and error messages before using that result. The project's command reference describes these options.
Deal with TAR.ZST
If your input is Project.tar.zst, a two-stage workflow avoids depending on Zstandard support in the installed tar itself:
zstd -d -k "Project.tar.zst" -o "Project-expanded.tar"
tar -tf "Project-expanded.tar"
mkdir "ZST archive output"
tar -xvf "Project-expanded.tar" -C "ZST archive output"
Choose new output names and an empty destination. Proceed to the next command only after the previous one succeeds. This workflow keeps the original compressed file but also creates an intermediate TAR, so allow space for that TAR and the extracted files.
If the sender used a separate compression dictionary, a matching dictionary may be required. Ask for that dictionary and compatible tooling, or for a self-contained archive. A missing dictionary is different from a missing password. Renaming the extension fixes neither issue.
Open and extract in Kernir
The Mac download is coming soon. You can view the source and build instructions on GitHub. These steps describe the current app workflow.
Choose File › Open… (⌘O) and select the ZST. A standalone stream appears as an entry; a supported TAR.ZST displays its archive tree. Select the required entries and use File › Extract… (⌘E) to choose a destination.
You can save a copy in a supported writable format, such as ZIP, but Kernir cannot save it back as ZSTD or TAR.ZST. When reporting a problem, include the producing tool, whether the file is a standalone stream or tarball, and any dictionary requirements.
To try a small file with known contents, use the sample archive library. Substitute the downloaded sample's filename in the commands above.
Kernir.dmg, signed and notarized. Requires macOS 14 or later.
Related guides
App steps were checked against Kernir source code. Command examples were checked with test archives on Linux using libarchive and the named utilities, not in a new macOS session. Updated .
