Convert TZO to RAR Online (From LZO-Compressed Tarballs to WinRAR's Format)

What a TZO Archive Is Built From

A .tzo file is a tar archive compressed with lzop, a tool built around Markus Oberhumer's LZO compression library — lzop's own documentation describes .tzo as a shorthand for .tar.lzo, the same format under a different, shorter name. LZO's defining trait is speed: it decompresses far faster than gzip, bzip2, or xz, at the cost of a noticeably weaker compression ratio, which is exactly why it's used in embedded Linux firmware and time-sensitive backup pipelines where the speed of unpacking data matters more than how small it gets stored.

RAR is a proprietary archive format created by Eugene Roshal, first released in 1993, now maintained through WinRAR and the free-to-use unrar/rar command-line tools. Its current version, RAR5, uses its own proprietary compression algorithm distinct from LZO, DEFLATE, or LZMA, generally landing closer to 7-Zip's LZMA in typical compression ratio than to lzop's much lighter-weight approach. Converting a .tzo archive to RAR means fully decompressing the LZO-compressed tar stream, then rebuilding the same file contents inside RAR's own proprietary container from scratch.

A Closed Compression Algorithm Replacing an Open One

LZO is openly documented and its source code is publicly available, which is exactly why GNU tar can integrate with it directly through a simple --lzop flag that calls the external, freely available lzop binary. RAR's actual compression algorithm, by contrast, has never been published as an open specification the way DEFLATE, bzip2, or even LZMA have been — WinRAR and the official unrar/rar tools are the only fully compliant implementations, and any format-level understanding of exactly how RAR5 compresses data comes from reverse engineering rather than an open document like PKWARE's ZIP specification or the Tukaani Project's own .xz file format specification.

Functionally, what this means for someone converting from .tzo to RAR is straightforward even without knowing RAR's internal algorithm details: the new archive will almost certainly compress tighter than the LZO-based original on typical data, since RAR's algorithm targets compression ratio in a way LZO deliberately doesn't, but creating or fully verifying that RAR archive requires WinRAR or the official rar tool specifically, rather than any general-purpose open-source library capable of reading arbitrary compression formats.

RAR also supports splitting an archive into multiple numbered volumes and adding an optional recovery record, extra redundant data stored inside the archive that lets WinRAR repair a certain amount of physical corruption in the file after the fact — a documented feature the LZO/tar combination behind a .tzo file has no equivalent for at all.

It's also worth separating the container question from the compression question here, since a .tzo file is really two layers stacked together. Tar itself stores files as sequential header-plus-data blocks with no built-in index of what's inside, and LZO compression simply wraps around that finished stream afterward. RAR, by comparison, is a self-contained archive format with its own per-file headers and internal structure — closer in that respect to ZIP or 7z than to a compressed tar stream — which is one more reason converting between the two isn't a simple recompression step but a genuine rebuild into a different kind of container.

What Rebuilding This Archive as RAR Gains and Costs

• Gain — a meaningfully smaller archive on typical data: RAR5's proprietary algorithm generally compresses tighter than LZO's speed-focused, simpler matching scheme.
• Gain — optional recovery record and volume splitting: RAR can rebuild a damaged archive using redundant recovery data and split large archives into fixed-size parts, neither of which the tar-plus-lzop combination supports natively.
• Lose — LZO's fast decompression: RAR's decompression, while reasonably efficient, doesn't match LZO's near-instant unpacking on constrained or embedded hardware.
• Lose — open, freely implementable compression: LZO's source is public; RAR's core algorithm isn't, meaning full compatibility depends specifically on WinRAR or the official rar/unrar tools.
• Gain — AES-256 encryption: RAR natively supports strong encryption for archive contents, which the LZO/tar pairing has no built-in equivalent for.
• Unchanged — the underlying file data: both LZO and RAR's compression are lossless, so extracted files remain identical regardless of which format stored them.

Which Tools Actually Handle Each Side of This Conversion

Reading the original .tzo file requires the lzop utility itself, or GNU tar invoked with its --lzop flag, since mainstream Windows and macOS archive managers generally don't support LZO-based decompression out of the box. This is a real, current gap, and it's specifically why .tzo files tend to originate from and stay within Linux, Unix, or embedded-systems environments that already have lzop installed.

Creating a genuinely valid, fully compliant RAR archive on the other end requires WinRAR on Windows or the official rar command-line tool on Linux and macOS; the free 7-Zip and most open-source archive tools can extract RAR archives but cannot create new ones, since RAR's compression algorithm isn't openly licensed for third-party encoders the way ZIP's DEFLATE is. This asymmetry — broad extraction support, narrow creation support — is a real, documented characteristic of the RAR format that anyone producing new RAR archives needs to plan around.

Specific Problems Reported Around This Conversion

A documented complaint in cross-platform build and deployment threads involves a .tzo archive produced on a Linux build server that a Windows-based reviewer can't open at all, since neither 7-Zip nor WinRAR includes native LZO decompression — teams resolve this either by installing an lzop build for Windows or by having the Linux side rebuild the archive as RAR or another broadly supported format before sharing it for review.

A second, recurring issue involves attempting to create a RAR archive using a free or open-source tool that only supports RAR extraction, not creation — some users mistakenly assume any tool capable of opening a RAR file can also produce one, and are surprised when the "save as RAR" option simply doesn't exist in a given application. WinRAR itself, or the official command-line rar tool, is required specifically for creating new, fully valid RAR archives.

A third pattern shows up in embedded-firmware discussions specifically: a firmware image rebuilt as RAR for easier distribution to a team turns out to be entirely unusable for actually flashing onto the target device, because the device's bootloader was written to decompress LZO-compressed data directly and has no RAR decoder at all — RAR is useful here purely for sharing the file among people, not for the version that ultimately gets deployed to the hardware itself.

A fourth, more general complaint involves file size expectations after this specific conversion: some users report a RAR archive coming out only marginally smaller than the original .tzo file, rather than dramatically smaller as expected, when the source data was already something LZO happens to compress reasonably well, such as certain structured log formats. Compression ratio differences between algorithms are real but data-dependent — they show up most clearly on the more compressible file types LZO is comparatively weaker on, like plain text and source code, and less dramatically on data that was already fairly compact going in.

LZO's Open Speed Focus Set Beside RAR's Proprietary Ratio Focus

Questions About Moving From LZO Speed to RAR's Compression

Why would I need to create a RAR file specifically, rather than any tool that reads RAR?
Because RAR's core compression algorithm is proprietary. Tools that only implement extraction, like some free archive managers, can open existing RAR files but can't create new, fully valid ones — only WinRAR or the official rar tool can.

Will my archive get smaller after converting from .tzo to .rar?
Generally, yes. RAR5's compression algorithm typically compresses more tightly than LZO's speed-focused, simpler matching scheme on most typical data.

Can I open a .tzo file directly in WinRAR?
No. WinRAR doesn't include native LZO decompression support. The lzop utility, or GNU tar's --lzop flag, is needed first to extract the original archive.

Does RAR's recovery record actually help if my archive gets corrupted?
Yes, if it was added when the archive was created. RAR's optional recovery record stores redundant data specifically to let WinRAR repair a limited amount of physical file damage after the fact.

Should I use RAR for a firmware image meant to be flashed onto embedded hardware?
Only for sharing it with people. If the device's bootloader expects LZO-compressed data directly, converting the actual deployed image to RAR will make it unusable on that hardware.

Why is my new RAR file only slightly smaller than the original .tzo file?
Compression gains between algorithms depend heavily on the data itself. Files that were already fairly compact or not very repetitive to begin with show a smaller improvement than highly repetitive data like plain text or source code.