Open a .zst online
Decompress (zstd -d) a .zst file in your browser — no command line, no upload.
Drop your .zst anywhere on this page
Decompressed entirely in your browser — your file is never uploaded.
A .zst is a single file compressed with Zstandard — log.zst, backup.sql.zst, data.json.zst. It is not a multi-file container: zstd is a stream compressor, so a lone .zst holds exactly one file, and "opening" it means undoing the zstd compression (the zstd -d operation) to get that one file back. ZipTool does it in your browser with a zstd decoder bundled into the page: you drop the .zst on it and the decompressed file opens immediately, with nothing uploaded and nothing installed.
You open the page, drop the .zst onto it (or paste a direct URL), and the original file renders locally — text and code in a syntax-highlighting editor, images, PDFs, audio, and video depending on what was inside. The decode runs entirely in your tab; the network is used only to load the page.
.zst versus .tar.zst — they are not the same
The two extensions are constantly confused, and the difference matters. A lone `.zst` is one compressed file — report.csv.zst decompresses to one report.csv. A `.tar.zst` (or .tzst) is a tar bundle of many files that was then compressed with zstd — it opens as a whole folder tree. If you expected many files from a .zst and got one, you almost certainly have a mistyped .tar.zst.
ZipTool handles both honestly: a .zst opens as the single file inside it, and a .tar.zst opens as a folder tree — see open a .tar.zst online. The gzip-flavoured siblings work exactly the same way: open a .gz online for a single gzipped file and open a .tar.gz online for the tarball form.
How to open a .zst in your browser
No zstd, no terminal, no install. The page decodes the stream locally.
- Go to ZipTool and drag the
.zstonto the page (or use the file picker, or paste a URL). - The single file inside is decompressed and opened — text and code show in the editor, images and PDFs render, audio and video play.
- Download the decompressed file to keep it, or search and read it in place.
- Nothing is uploaded — confirm it by opening a .zst and turning off your internet; viewing keeps working.
Why zstd — and why you keep meeting .zst files
Zstandard was released by Facebook in 2015 (standardized as RFC 8878 in 2021) by the author of LZ4, with a deliberate brief: compress meaningfully better than gzip while decompressing much faster. It delivers — at its default level zstd typically produces files roughly 13% smaller than gzip while decompressing several times faster, which is why performance-sensitive pipelines keep adopting it. A zstd stream is a sequence of frames, each starting with the magic bytes 28 B5 2F FD, and each frame header can optionally carry the decompressed size, so a well-formed .zst often knows how big it will get. There is also a dictionary mode: train a small dictionary on samples of your data, and many small similar records compress far better than they ever would standalone.
That engine now shows up everywhere. Fedora has compressed its RPM package payloads with zstd since Fedora 29; the Linux kernel uses it for compressed modules, and Btrfs and SquashFS offer zstd compression; and GNU tar grew a --zstd flag, which is how most .tar.zst files are created. Meeting a bare .zst usually means one of those systems handed you a single compressed file.
Honest limits
A browser-based zstd decompressor is simple and reliable, with a couple of boundaries.
- A .zst is one file, not a folder. zstd compresses a single stream; it is not a packager. If you need many files out, you have a
.tar.zst, not a.zst— see open a .tar.zst online. - zstd frames carry no filename. gzip has an optional FNAME field that records the original name; zstd has no equivalent, so the decompressed file takes the container's name minus the
.zst—data.json.zstopens asdata.json. - xz and bzip2 are supported too. A lone
.xzopens on open an .xz file online and a.bz2on open a .bz2 online; their tarball forms have their own pages (`.tar.xz`, `.tar.bz2`). LZ4 is not handled; use the command line or a desktop tool for that. - zst is a source, never a target. ZipTool's converter accepts
.zstand.tar.zstarchives as input and repacks them as ZIP, TAR, or TAR.GZ — it never writes.zstoutput.
Frequently asked questions
How do I open a .zst file online?
Open the page and drop your .zst onto it. ZipTool decompresses the file inside it in your browser — no command line, no install, no upload. The original file opens immediately (text, code, image, PDF, audio, or video depending on what was compressed), and you can read or download it.
What is the difference between .zst and .tar.zst?
A .zst is a single file compressed with zstd — it decompresses to one file. A .tar.zst is a tar bundle of many files that was then compressed with zstd — it opens as a folder tree. If you expected many files from a .zst, you likely have a .tar.zst. ZipTool opens both: a .zst as one file (this page), a .tar.zst as a tree (/tar-zst).
Is zstd better than gzip?
For most uses, yes: at comparable levels zstd compresses roughly 13% smaller than gzip and decompresses several times faster, and its dictionary mode shines on many small similar files. gzip's remaining edge is ubiquity — every operating system ships gunzip, while zstd tooling sometimes needs installing. Both are open and patent-free.
Do you upload my .zst file?
No. The file is decompressed entirely in your browser; your contents are never sent to a server, never stored, and never handed to a third party. Confirm it in DevTools — the Network tab shows no upload — and by disconnecting from the internet after the page loads: viewing keeps working.
Can it open .xz, .bz2, or .zst files?
All three — a lone .zst opens right here, an .xz on open an .xz file online, and a .bz2 on open a .bz2 online; the tarball forms are .tar.zst, .tar.xz, and .tar.bz2. LZ4 is not supported; use the command line or a desktop tool for that.