CONVERT
LZ4 → XZ
Fast, secure LZ4 to XZ conversion. No registration required.
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Opening note — LZ4 is an archive format that bundles multiple files into a single compressed container. The XZ you want is two clicks away. Going from LZ4 to XZ converts the wrapper around a collection of files. If your workflow speaks XZ and the backup you were sent is a LZ4, this tool rewraps the bundle for you without asking you to extract and re-compress by hand — and without leaving a scratch folder behind. A quick refresher — LZ4 is an archive format that bundles multiple files into a single compressed container. By contrast, XZ is the LZMA2-based compression format used for tight compression of source tarballs.
LZ4 Compressed
Source formatLZ4 is an extremely fast lossless compression algorithm focused on speed over compression ratio. It can compress at over 500 MB/s per core and decompress at multiple GB/s, making it the standard choice for real-time and in-memory compression.
XZ Compressed
Target formatXZ provides very high compression ratio using LZMA2, common in Linux packages.
Why convert LZ4 to XZ
Some XZ formats support features LZ4 lacks: solid compression across many small files, per-file encryption, streamable headers. Repacking a legacy LZ4 into a modern XZ is how you opt into those features without changing any of the files inside.
HOW TO CONVERT
LZ4 → XZ
Start the job
Upload a LZ4; 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 XZ codec at a balanced default level.
Save the result
Download the XZ when ready. Nothing about the original contents is logged or retained.
Common Use Cases
Per-file encryption
XZ formats supporting AES encryption let you ship a passworded archive without relying on filesystem-level protection.
Long-term digital preservation
Libraries and archives standardise on XZ for decades-long retention; convert incoming LZ4 deposits on receipt.
Email-friendly bundles
Corporate mail filters strip LZ4 attachments but allow XZ; switching container is often the only fix.
Batch vendor submissions
Submission systems (journals, marketplaces, clients) mandate XZ. Non-compliant LZ4 uploads silently fail.
LZ4 vs XZ — Strengths and limitations
What each format does best, and where it falls short.
LZ4 Strengths
- Decompression speed — approaches memcpy throughput.
- Very fast compression — can keep up with SSD write speeds.
- Stable format — reference implementation unchanged for years.
- Widely deployed in databases, filesystems, and kernels.
- BSD-licensed library.
Limitations
- Compression ratio lags gzip by 20-30%.
- Not designed for long-term archival where ratio matters.
- Older than zstd, which beats LZ4 at comparable speed at slightly better ratio.
XZ Strengths
- Best-in-class compression ratio among mainstream tools.
- Streaming-capable — can pipe through network.
- Multi-threaded compression available.
- Mature on every Linux distribution.
- Supports integrity checking (CRC32, CRC64, SHA-256).
Limitations
- Slow compression at high levels — 3-5× slower than gzip.
- Memory-hungry: xz -9 can need 700+ MB to compress.
- 2024 supply-chain backdoor damaged trust in the project.
LZ4 vs XZ — Technical specifications
Side-by-side comparison of the technical details.
| Specification | LZ4 | XZ |
|---|---|---|
| MIME type | application/x-lz4 | application/x-xz |
| Extensions | .lz4 | .xz, .txz |
| Algorithm | LZ77 variant with fast byte-level parsing | LZMA2 |
| License | BSD 2-Clause (library), GPL v2 (CLI) | — |
| Typical integrations | Linux kernel, ZFS, Kafka, RocksDB, Cassandra | — |
| Standard | — | The .xz File Format specification 1.1.0 |
| Integrity checks | — | None, CRC32, CRC64, SHA-256 |
LZ4 vs XZ — Typical file sizes
Approximate file sizes for common scenarios.
LZ4
- Text file 40-60% of original
- Already-compressed data (JPEG, MP4) 99%+ (no gain)
- Database page (typical) 55-70% of original
XZ
- Text/source archive 15-25% of original
- Linux kernel (.tar.xz) ~125 MB
- Firefox source code ~600 MB
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) — XZ formats that support it can shrink 20-50% over per-file compression.
- When the LZ4 contains symlinks, test that they still resolve after conversion; some XZ formats represent them differently on Windows vs Unix.
- Deterministic timestamps (via Advanced → reset mtimes) make the XZ reproducible for CI artefact verification; otherwise two "identical" conversions will produce slightly different bytes.
Frequently Asked Questions
Frequently Asked Questions
Yes. The free tier accepts files up to 100 MB without registration, email capture or watermarks. 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 LZ4 and XZ use different compression codecs, every entry is decompressed from the LZ4 and re-compressed for the XZ. 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 LZ4 and the XZ 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 LZ4 used an older codec like Deflate. Against modern LZMA2 / Zstd XZ 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 XZ can be re-encrypted with a password of your choice (AES where the target format supports it).
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Secure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.