You download a backup, database dump, Linux package, or development archive and end up with a file called:
backup.tar.zst
Double-click it — and macOS does not know what to do.
What is a ZST file?
ZST is short for Zstandard , a modern lossless compression format designed for fast compression and especially fast decompression. It is increasingly used for backups, software packages, server data, and other large files. The format is open and standardized, but macOS still does not provide a simple built-in way to open it. Learn more about Zstandard.
There are two common variants:
- A .zst file contains one compressed file.
- A .tar.zst file contains a TAR archive that was subsequently compressed with Zstandard.
That second variant can make manual extraction slightly awkward: first the Zstandard layer must be removed, then the resulting TAR archive must be unpacked.
The Terminal solution
If you already have the necessary command-line tools installed, you can extract the files in Terminal. That works well for developers who regularly handle Zstandard archives.
For everyone else, installing a package manager and remembering command-line options is a lot of setup for what should be a simple job: drop in a file and get its contents back.
Open ZST files with drag and drop
unpackZST for Mac provides that missing step.
Drop one or several .zst or .tar.zst files onto the app and start the extraction. For TAR-based archives, unpackZST can automatically continue with the enclosed archive instead of leaving you with another file to open manually.
Extraction runs locally on your Mac. Files are not uploaded, no account is required, and there is no background service waiting when the app is closed.
It is a small utility for a specific problem — and once that unfamiliar .zst file appears in your Downloads folder, it is exactly the tool you need.
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