CONVERT GZ → ZST (GZ to ZST)
Fast, secure GZ to ZST conversion. No registration required.
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HOW TO CONVERT GZ → ZST
Start the job
Upload a GZ; we read its header to learn how many entries it carries and the compression method used.
Transcode container
Every entry is decompressed, then recompressed with the ZST codec at a balanced default level.
Save the result
Download the ZST when ready. Nothing about the original contents is logged or retained.
Setup: GZ is the gzip DEFLATE compression format, typically wrapped around TAR for Unix distributions. Goal: an interchangeable ZST. Need to turn a GZ into a ZST? The conversion is lossless by definition — archive formats only store file data plus metadata, and every mainstream archive supports the same primitives. File names, folder structure, timestamps and attributes round-trip exactly. In practice GZ is the gzip DEFLATE compression format, typically wrapped around TAR for Unix distributions. On the other end, ZST is a compression/archive format used to package or shrink files.
Why convert GZ to ZST
Some ZST formats support features GZ lacks: solid compression across many small files, per-file encryption, streamable headers. Repacking a legacy GZ into a modern ZST is how you opt into those features without changing any of the files inside.
GZ vs ZST — Technical specifications
Side-by-side comparison of the technical details.
GZ
- MIME type
- application/gzip
- Extensions
- .gz, .tgz (with tar)
- Algorithm
- DEFLATE (LZ77 + Huffman coding)
- Standard
- RFC 1952 (gzip), RFC 1951 (DEFLATE)
- Header
- 10 bytes: magic, method, flags, mtime, extra, filename, comment, crc, isize
- MIME Type
- application/gzip
- Extension
- .gz
- Category
- Archives & Compressed
- Full Name
- Gzip Compressed
- Conversion Engine
- ARCHIVE
ZST
- MIME type
- application/zstd
- Algorithm
- LZ77 variant + entropy coding (FSE/Huffman)
- Standard
- RFC 8478 (2018)
- MIME Type
- application/zstd
- Extension
- .zst
- Category
- Archives & Compressed
- Full Name
- Zstandard Compressed
- Conversion Engine
- ARCHIVE
- Compression levels
- 1-22 (plus negative "fast" levels)
| Specification | GZ | ZST |
|---|---|---|
| MIME type | application/gzip | application/zstd |
| Extensions | .gz, .tgz (with tar) | — |
| Algorithm | DEFLATE (LZ77 + Huffman coding) | LZ77 variant + entropy coding (FSE/Huffman) |
| Standard | RFC 1952 (gzip), RFC 1951 (DEFLATE) | RFC 8478 (2018) |
| Header | 10 bytes: magic, method, flags, mtime, extra, filename, comment, crc, isize | — |
| MIME Type | application/gzip | application/zstd |
| Extension | .gz | .zst |
| Category | Archives & Compressed | Archives & Compressed |
| Full Name | Gzip Compressed | Zstandard Compressed |
| Conversion Engine | ARCHIVE | ARCHIVE |
| Compression levels | — | 1-22 (plus negative "fast" levels) |
GZ vs ZST — Strengths and limitations
What each format does best, and where it falls short.
GZ Strengths
- Patent-free, royalty-free — that was the whole point in 1992.
- Universally supported on every OS.
- Fast compression and extremely fast decompression.
- Preserves original timestamps and filenames in the header.
- Streamable — can compress/decompress over pipes.
Limitations
- Compresses one file at a time — needs tar for multi-file archives.
- Older algorithm — Zstandard, xz, and brotli all beat it on ratio.
- Single-threaded in the reference implementation (pigz fixes this).
ZST Strengths
- Extremely fast decompression (~2 GB/s on modern CPU).
- Scalable: very fast at level 1, near-xz ratios at level 22.
- Dictionary support for small-payload efficiency.
- Multi-threaded by default.
- Standardized (RFC 8478), BSD-licensed reference.
Limitations
- Newer than gzip/bzip2 — some legacy tools still lack support.
- At extreme compression levels, xz can still win on ratio.
- Memory usage at high levels is significant.
Quality & Compatibility
File attributes that both formats understand (modification time, Unix permissions, symlinks) round-trip cleanly. Obscure metadata that one side lacks (e.g., advanced ACLs in one direction) is dropped silently rather than causing the conversion to fail.
Tips for Best Results
- Archives with thousands of tiny files benefit hugely from "solid" compression (one of the Advanced options) — ZST formats that support it can shrink 20-50% over per-file compression.
- When the GZ contains symlinks, test that they still resolve after conversion; some ZST formats represent them differently on Windows vs Unix.
- Deterministic timestamps (via Advanced → reset mtimes) make the ZST reproducible for CI artefact verification; otherwise two "identical" conversions will produce slightly different bytes.
Frequently Asked Questions
Yes. The free tier accepts files up to 25 MB without registration, email capture or watermarks; paid plans go up to 2 GB. Paid plans raise the size cap, enable batch conversions and provide a REST API for automation, but nothing on the free tier is quality-limited — the output is exactly the same as on any paid plan.
Yes — because GZ and ZST use different compression codecs, every entry is decompressed from the GZ and re-compressed for the ZST. The uncompressed data is identical on both sides, and the re-compression happens entirely inside our processing container.
Uploads run over HTTPS, files are processed in isolated containers, and both the source GZ and the ZST output are auto-deleted within two hours. No account is required, file contents are never logged, and KaijuConverter does not use uploads for AI training. The paid plan adds a signable data-processing agreement for regulated workflows.
Usually yes, modestly, when the original GZ used an older codec like Deflate. Against modern LZMA2 / Zstd ZST containers expect 10-30% savings on mixed content and almost no change on pre-compressed payloads. Advanced → compression level lets you trade speed for ratio.
Most files finish in well under a minute. Small images and documents are typically ready in a few seconds; large video or audio files scale roughly with duration. Upload speed from your network is usually the dominant factor, not server time.
Yes. Provide the password during upload; we use it only to decrypt inside the processing container and never log or persist it. The resulting ZST can be re-encrypted with a password of your choice (AES where the target format supports it).
Gzip Compressed
Source formatGzip is a single-file compression format based on the DEFLATE algorithm. It is most commonly paired with TAR to create .tar.gz archives and is the standard compression for web content delivery.
Zstandard Compressed
Target formatZstandard (Zstd) is a fast lossless compression algorithm developed by Yann Collet at Facebook. It provides compression ratios comparable to zlib while being 3-5x faster at both compression and decompression, making it ideal for real-time data processing.
Going the other way? Convert ZST back to GZ with the same engine.
Common Use Cases
Share across platforms
Send ZST files to anyone without worrying about whether they have the right software for GZ.
Embed in documents
Drop ZST output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
ZST often produces smaller files than GZ for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
GZ vs ZST — Typical file sizes
Approximate file sizes for common scenarios.
- Plain text file 25-40% of original
- HTML page 20-30% of original
- Source code archive 15-30% of original
- Default level 3 on source code 28-35% of original
- Level 22 ultra on source code 14-18% of original
- Linux kernel (.tar.zst, level 19) ~130 MB
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Related comparisons
See these formats side by side to understand which fits your use case best.
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Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.