Convert TAR.LZO to 7Z Online (Trading Decompression Speed for Compression Ratio)

A Format Built for Speed Meets a Container Built for Ratio

A TAR.LZO file pairs tar's plain 512-byte-block container with lzop's LZO compression, an algorithm whose own documentation states its design goal as fast decompression above almost every other consideration, including file size. 7-Zip's native 7z format, released by Igor Pavlov in 1999, was built with the opposite priority: its own container carries a built-in file index, and its default LZMA or LZMA2 compression is tuned specifically to squeeze data down as far as reasonably possible, at whatever CPU cost that requires.

Converting from TAR.LZO to 7z means fully decompressing lzop's LZO-compressed blocks back into the plain tar byte stream, reading tar's headers to recover each file's name and Unix permission bits, and then re-encoding everything inside 7z's own container using LZMA2. Because 7z's format was designed primarily around Windows file attributes, the Unix ownership and permission metadata tar's headers carry doesn't map onto 7z's own fields the same consistent way across every conversion tool, a real, documented gap depending on which specific software performs the conversion.

Lzop's own per-block checksum structure — Adler-32 by default, or CRC-32 if requested — also disappears entirely once the archive is rebuilt as 7z, since 7z uses its own CRC-32 checks recorded per file in its internal index rather than per compressed block the way lzop's format does. The practical effect is the same integrity protection at the level of individual files, just organized differently under the hood.

No Entropy Coding at All Against a Dictionary Measured in Gigabytes

LZO's default lzo1x_1 method finds repeated byte sequences and replaces them with back-references, but deliberately skips the entropy-coding stage that most other general-purpose compressors add on top of that matching step — a stage LZMA2 applies fully, alongside a dictionary size configurable up to 1,536 MB (1.5 GB) in 7-Zip's reference implementation, versus LZO's comparatively narrow effective matching range. That combination — an extra coding stage plus a vastly larger search range — is why 7z routinely produces a noticeably smaller archive than the same content compressed with LZO, sometimes by a wide margin on redundant data.

The cost runs in the opposite direction on speed. LZO's own documentation and independent benchmarks consistently show it decompressing faster than LZMA2, gzip's DEFLATE, or bzip2, since there's simply less decoding work involved once the LZ-style matching is undone. LZMA2 at 7-Zip's higher compression settings can also take noticeably longer to compress in the first place than LZO's simplified scan does, a real, measured cost for archives that get rebuilt often rather than compressed once and read back rarely.

LZO's licensing also differs from what 7-Zip uses: the LZO library and lzop utility are released under the GNU General Public License, version 2 or later, while 7-Zip's own source code is released under the GNU LGPL with some modules under a separate BSD-style license — a real, if secondary, consideration for anyone embedding either compressor's code directly into their own software rather than simply using the finished command-line tools.

What Trading LZO's Speed for 7Z's Ratio Actually Gains and Costs

• Gain — a meaningfully smaller archive: LZMA2's entropy coding and much larger dictionary generally beat LZO's simpler matching by a wide margin on compressible data.
• Lose — LZO's fast decompression: 7z's LZMA2 decodes slower than LZO, which matters directly if the archive feeds a genuinely time-critical process like a device bootloader.
• Gain — mainstream desktop tool support: 7-Zip and p7zip are widely available on Windows, macOS, and Linux, unlike LZO's much narrower tooling.
• Lose — some Unix permission and ownership detail: 7z's attribute handling wasn't designed primarily around Unix mode bits the way tar's own headers were.
• Gain — built-in AES-256 encryption: 7z supports encrypting file contents and, optionally, the file list itself, something TAR.LZO has no equivalent for at all.
• Unchanged — the actual file contents: both LZO and LZMA2 are lossless, so extracted files remain byte-for-byte identical regardless of which format compressed them.

Documented Support Gaps Between These Two Specific Formats

Reading a TAR.LZO file requires the lzop utility specifically, or GNU tar used with its --lzop flag, since 7-Zip, WinRAR, and mainstream Windows or macOS tools generally don't include native LZO decompression at all — a real, current limitation that keeps TAR.LZO mostly confined to Linux, Unix, and embedded-systems environments that already have lzop installed for a specific purpose.

7z sits at the opposite end of that gap: 7-Zip on Windows and its p7zip port on Linux and macOS both create and read 7z archives natively, and PeaZip supports the format on all three platforms as well, making 7z considerably more broadly reachable on ordinary desktop systems than TAR.LZO ever is by default. This asymmetry is a large part of why TAR.LZO-to-7z conversions get requested in the first place — moving content out of a format most desktop users can't open at all and into one nearly any current archive tool handles without extra setup.

Programming language ecosystems reflect the same gap: Python's standard library includes a lzma module for reading and writing 7z-compatible LZMA streams directly, while working with LZO-compressed data generally requires a separate, less commonly maintained third-party binding. This matters for anyone building automated conversion tooling around either format, since LZMA support can usually be assumed available in a modern language runtime, while LZO support typically has to be added deliberately.

Real Reports From Embedded-to-Desktop Conversion Attempts

A recurring, documented complaint involves a developer trying to open a TAR.LZO firmware image pulled from an embedded Linux build on an ordinary Windows machine using 7-Zip, and finding it isn't recognized at all — the practical fix reported is installing lzop through a compatibility layer or converting the file to a more broadly supported format like 7z before it needs to be inspected outside its original embedded environment.

A second pattern, reported from the opposite direction, involves a firmware image converted to 7z for easier review or storage turning out to be unusable for actual deployment, if the target device's bootloader was specifically written to decompress LZO-compressed data and has no LZMA decoder built into its limited firmware — in these cases, the version reviewed on a desktop and the version actually flashed onto hardware legitimately need to stay in two different formats.

A third report involves the noticeably longer time a large TAR.LZO archive takes to convert into 7z at higher compression settings, compared with how quickly the original LZO compression ran — this isn't a malfunction, it's the expected cost of LZMA2's much larger dictionary and its added entropy-coding stage doing meaningfully more work than LZO's simplified matching ever attempted.

A fourth, more procedural complaint involves scripts and automation pipelines built around a specific tar flag that assume a fixed compression method — a script hardcoded to call tar with the --lzop flag for extraction will simply fail against a 7z file rebuilt from that same content, since 7z isn't a tar-based format at all and needs 7-Zip or p7zip specifically rather than any variation of a tar command. Updating downstream scripts to match the new tool, rather than assuming a flag can stay the same, is a real, practical step this conversion requires.

LZO's Narrow Speed Focus Set Against 7Z's Ratio-First Design

Questions About Replacing LZO Compression With 7-Zip's Container

Will my archive get noticeably smaller after converting TAR.LZO to 7z?
Usually, often by a wide margin, since LZMA2's much larger dictionary and its added entropy-coding stage both do work that LZO's simplified matching deliberately skips.

Why can't I open a TAR.LZO file with 7-Zip directly?
7-Zip generally doesn't include native LZO decompression. The lzop utility, or GNU tar's --lzop flag, is needed to decompress the original archive before its contents can be repackaged.

Is 7z's decompression as fast as LZO's?
No. LZO is specifically built to decompress faster than nearly any other common algorithm, including LZMA2, which is exactly why LZO gets chosen for time-critical embedded uses in the first place.

Should I convert a firmware image meant for a device's bootloader to 7z?
Not for the version actually deployed. If the bootloader expects LZO-compressed data directly, converting the deployed image to 7z will likely make it unusable on that specific hardware.

Does this conversion change any of the actual files?
No. Both LZO and LZMA2 are lossless compression methods, so every file extracted afterward is byte-for-byte identical to what was originally inside the TAR.LZO archive.