Convert LHA to RAR Online (From a Frozen Format to a Licensed One)

One Decades-Frozen Format Meeting One Still Actively Sold Today

LHA, stored with either the .lha or .lzh extension, dates to 1988, when Haruyasu Yoshizaki's LHarc tool packaged files using LZSS-style matching combined with Huffman coding under the name LZHUF. It spread across Japanese bulletin board systems and became a standard archive format on Amiga computers, but the format and its historical tooling have seen no meaningful development in years. RAR, created by Eugene Roshal, is the opposite case: it's a proprietary format still owned and actively developed by RARLAB, sold as commercial software through WinRAR, with new format revisions released as recently as RAR5 in 2013.

Converting an LHA archive to RAR means decompressing every entry — most commonly compressed with LHA's -lh5- method, an 8 KiB window using static Huffman tables — and recompressing that data through WinRAR's own proprietary algorithm, which is the only legal way to produce a genuine RAR file, since RARLAB doesn't license out RAR's compression routines for other software to implement.

The gap between the two formats isn't just about age. LHA's specification has stayed effectively unchanged since its last active updates, defined by a small set of documented method tags (-lh0- through -lh7-) and header levels (0 through 3). RAR, by contrast, has gone through multiple major revisions — RAR2, RAR3, and the current RAR5, adopted as WinRAR's default since version 5.0 in 2013 — each adding features like larger dictionaries, stronger encryption, and recovery records that LHA's frozen design never received a chance to add.

Why RAR's Compression Reach Dwarfs LHA's by Design

LHA's most advanced method, -lh7-, caps its sliding window at 64 KiB, meaning the compressor can only match repeated data that occurs within about 64,000 bytes of itself — a limit that made sense on the floppy-disk-era hardware the format targeted in the late 1980s. RAR5's dictionary, by comparison, scales up to 4 GB, letting it find and eliminate repeated patterns across a vastly larger span of the same file, which is one of the clearest, most concrete reasons a RAR archive built from the same source data usually comes out noticeably smaller than the original LHA file.

RAR also supports "solid archive" mode, treating an entire set of files as one continuous stream so its algorithm can find matches across file boundaries, not just within each file separately. LHA has no equivalent solid-compression mode; each entry is compressed and tagged with its method independently. For a folder holding many small, similar files — a common situation with old archived source code or document collections — solid compression in RAR typically shrinks the total archive further than LHA's per-file approach ever could.

What Moving From LHA to RAR Actually Changes

• Gain — typically a smaller archive: RAR5's much larger compression dictionary and solid-archive option generally beat LHA's capped 64 KiB window on the same data.
• Gain — AES-256 encryption with encrypted filenames: RAR encrypts the file list itself by default under its AES mode; the classic LHA format has no encryption feature at all.
• Lose — free, no-cost creation: WinRAR is shareware requiring a paid license after its 40-day trial, while historical LHA-creating tools were typically free.
• Lose — the narrow legacy compatibility LHA still has: Amiga programs and old Japanese-market software that specifically expect .lha or .lzh files won't recognize a RAR archive.
• Gain — a recovery record option: RAR5 can embed Reed-Solomon error-correction data letting WinRAR repair a damaged archive, something neither LHA nor most legacy formats offer.
• Gain — active bug fixes and format maintenance: RARLAB continues to update WinRAR and the RAR format, unlike LHA's tooling, which has had no real development for years.
• Lose — the small, simple archive structure LHA used: RAR's proprietary format and multiple internal revisions (RAR2, RAR3, RAR5) make it considerably more complex to parse than LHA's small, documented set of method tags and header levels.

Who Can Actually Create Each of These Formats, and Who Can Only Read Them

Creating a genuine RAR file requires WinRAR or RARLAB's own command-line rar tool specifically — no free or open-source program, including 7-Zip or PeaZip, is licensed to write the RAR format, though several of them can open and extract existing RAR archives. Creating an LHA file today is arguably even more limited in practice, since the tools historically used to build them have had no meaningful updates in years, and current mainstream archivers overwhelmingly treat LHA/LZH as something to read, not something to produce.

On the reading side, WinRAR itself lists LZH among the "other" formats it can open and extract, alongside JAR, TAR, and GZ — meaning the same software used to create the RAR archive can also open the original LHA file being converted. Standard 7-Zip supports neither creating RAR nor opening LHA/LZH natively; PeaZip is one of the few current tools that lists LHA/LZH among its natively supported formats for extraction, while depending on WinRAR or RARLAB's engine for genuine RAR creation.

This puts WinRAR in a convenient position for this specific conversion: since it can already open the source .lzh file directly, the entire LHA-to-RAR path can, in principle, run through a single program rather than needing one tool to extract LHA and a separate one to build the RAR archive afterward — a genuine practical advantage over converting LHA into formats that WinRAR itself has no read support for at all.

Documented Problems Behind Moving Old LHA Files Into RAR

The starting complaint in most of these conversions is the same one that applies to LHA generally: nothing on hand opens the old .lzh file, because Windows never included native LHA support and the standard 7-Zip build doesn't either, so a specific extractor like PeaZip has to be tracked down before anything else can happen, RAR conversion included.

A second issue specific to this pairing is the WinRAR trial nag screen that appears on every launch after 40 days — RARLAB's own licensing terms describe WinRAR as remaining fully functional past the trial but requiring a paid license for continued use, with the nag screen as the enforcement mechanism rather than a malfunction. Anyone converting many old LHA archives to RAR in bulk should expect that reminder to keep appearing unless a license is purchased.

A third, older concern involves the LHA source archives themselves: documented vulnerabilities (CVE-2004-0234 and CVE-2004-0235) let a maliciously crafted LHA file trigger a buffer overflow or write files outside the intended extraction folder in the Unix lha tool through version 1.14. Extracting old, untrusted LHA archives with current, patched software before repacking them as RAR avoids carrying that specific, decades-old risk forward.

A fourth pattern involves garbled filenames, specifically for archives built on Japanese-locale systems that stored names using Shift-JIS encoding. If the tool extracting the original LHA archive assumes a different encoding, the filenames come out corrupted before the files are even repacked into RAR, meaning the resulting archive inherits already-broken names rather than developing a new problem of its own. Using an extractor that correctly detects or lets the user choose Shift-JIS before conversion avoids this.

LHA Compared With RAR5

Questions About Converting LHA Archives Into RAR

Do I need WinRAR to open the RAR file after converting from LHA?
Not necessarily to open it — 7-Zip and other free tools can extract RAR archives. Creating a genuinely new RAR file, though, requires WinRAR or RARLAB's own rar tool, since no other software is licensed to write the format.

Will the RAR file be smaller than the original LHA archive?
Usually, yes. RAR5's much larger compression dictionary and optional solid-archive mode typically outperform LHA's capped 64 KiB window, though actual savings depend on what's inside the archive.

Can I add a password when converting LHA to RAR?
Yes. RAR supports AES-256 encryption with filenames encrypted by default; the classic LHA format never included any encryption option.

Why does WinRAR keep showing a trial reminder?
Because it's shareware with a 40-day trial. It keeps functioning afterward but displays a licensing reminder on every launch, which RARLAB describes as intentional, not a bug.

What opens the original LHA file so I can convert it in the first place?
PeaZip lists native LHA/LZH support, and WinRAR itself can extract (though not create) LZH files. Standard 7-Zip includes neither capability without a separate plugin.