Convert Files to LHA Online (A Format Almost Nothing Still Writes)

What Packing Files Into LHA Actually Means Today

LHA, also known by its .lzh extension, is a Japanese archive format created in 1988 by Haruyasu Yoshizaki, whose tool LHarc reused the container structure of an earlier program called LArc while replacing its compression method with a new algorithm called LZHUF — a combination of LZSS-style dictionary matching and Huffman entropy coding. The format spread widely through Japanese bulletin board systems in the late 1980s and 1990s and became a standard archive type on Amiga computers, but LHA has had no meaningful active development for years now.

That history matters before creating a new .lha file, because the honest answer to "what will open this later" has gotten narrower every year. Windows has never shipped with built-in LHA support, the standard release of 7-Zip does not include it either, and the software that historically created LHA archives is largely unmaintained. Packing files into LHA today mostly makes sense for a specific, narrow reason — feeding an old system, an emulator, or a legacy workflow that genuinely still expects that exact format — rather than as a general-purpose archive choice.

The Compression Method Actually Being Applied Inside an LHA Archive

LHA archives tag each stored file with a specific compression method rather than using one fixed algorithm throughout. Method -lh0- stores a file with no compression at all. Methods -lh1- and -lh2- use progressively larger sliding windows (4 KiB and 8 KiB) with dynamic Huffman coding, while -lh4- through -lh7- expand the window further — up to 64 KiB in -lh7- — using static, precomputed Huffman tables instead. The -lh5- method, with its 8 KiB window, became the effective default for most archives built during the format's peak years, which is the version most software creating LHA files today would still fall back on.

Every entry also carries a header level — 0 through 3 — controlling how metadata like the file's timestamp gets stored. The original level 0 and level 1 headers compress the year into a 7-bit DOS-style field that cannot represent years past 2011 correctly; files created after that point get misread as 1980 by software still using the old header format. Level 2 and 3 headers moved to a full 32-bit Unix timestamp instead, which avoids that specific bug but inherits the same year-2038 limit shared by other 32-bit time formats — a real limitation to know about before trusting timestamps in a freshly created archive to stay accurate indefinitely.

What Creating an LHA Archive Gains and Costs Compared With Modern Formats

• Gain — compatibility with genuinely old target systems: Amiga software, old Japanese-market programs, and some emulation or retrocomputing workflows still specifically expect .lha or .lzh files.
• Lose — the near-universal openability of ZIP or 7z: whoever receives an LHA archive today likely needs to track down and install a specific tool, since neither Windows nor the standard 7-Zip build supports it natively.
• Lose — active development and bug fixes: the format and its historical tools have had no meaningful updates in years, unlike ZIP, 7z, or TAR-based formats, which still receive maintenance from current software.
• Lose — competitive compression ratios: LHA's LZSS-plus-Huffman approach, with windows capped at 64 KiB even in its best method, was designed for 1980s-era hardware and compresses noticeably worse on typical modern data than 7z's LZMA or even ZIP's DEFLATE on many file types.
• Gain — a small, simple archive structure: LHA's header-and-method design is straightforward to implement, which is part of why it was adopted so widely on constrained early hardware in the first place.
• Lose — encryption or modern security features: the classic LHA/LZH format was never built with the password-protection or strong-encryption options that current formats like 7z or AES-enabled ZIP support.
• Lose — confidence in file timestamps decades out: level 0 and 1 headers can't represent years past 2011 correctly, and even the newer level 2 and 3 headers share the same 32-bit year-2038 limit found in other old timestamp formats.

Which Programs Can Still Genuinely Read an LHA File After It's Created

Before creating an .lha archive for someone else, it's worth knowing exactly what will and won't open it. Windows File Explorer has no built-in LHA support at any version. The standard release of 7-Zip doesn't include it either — a recurring request on 7-Zip's own support forum has gone unanswered for years, with maintainers pointing to a separate compression plugin as the only path to add it. WinRAR lists LZH among the formats it can open and extract, alongside JAR, TAR, and GZ, but like those, only for extraction — WinRAR itself only creates RAR and ZIP archives.

PeaZip is one of the few widely available current archivers that lists LHA/LZH directly among its natively supported formats for both opening and extracting. Beyond that, dedicated legacy tools and Amiga-native software remain the main options for full compatibility. Given that narrow list, sending someone a freshly created LHA archive today usually means confirming in advance that they have one of these specific tools available, rather than assuming it.

Japanese versions of older Windows releases were a partial exception, since Microsoft bundled LZH extraction support directly into those specific builds — part of why the format persisted in that market long after most of the world had already standardized on ZIP. That built-in support never extended to non-Japanese Windows editions, and current Windows versions carry no trace of it either, so relying on it today would mean targeting hardware and software that is itself now quite old.

Real Problems That Show Up When People Create or Receive New LHA Files

The most frequently reported issue is a recipient having no way to open the file at all, since neither their operating system nor their existing archiver — often 7-Zip specifically — includes LHA support out of the box. This isn't a sign of a corrupted archive; it reflects how narrowly supported the format has become, and the documented fix is installing an archiver like PeaZip that explicitly lists LZH support before trying anything else.

A second issue involves filenames containing non-English characters, particularly Japanese text — LHA archives built on Japanese-locale systems store filenames in Shift-JIS encoding by default, and if the receiving tool assumes a different encoding, the extracted filenames come out as garbled, unreadable text even though the file contents themselves are intact. Choosing an extraction tool that supports multiple filename encodings, or one that auto-detects Shift-JIS, avoids the problem.

A third, more serious concern applies specifically to old, unmaintained LHA software rather than the format's structure itself: documented vulnerabilities (CVE-2004-0234 and CVE-2004-0235) allowed a maliciously crafted LHA archive to trigger a stack-based buffer overflow or write files outside the intended extraction directory in the Unix lha tool through version 1.14. Distributions issued advisories and patches at the time, but any old, unpatched copy of that software still running today carries that same documented risk when opening an untrusted archive.

Creating an LHA File Versus Creating a Current Archive Format

Questions About Creating LHA Archives From Other Files

Should I use LHA for a new archive today?
Only if the specific recipient or system genuinely requires it, such as an Amiga program or legacy Japanese software. For general sharing, a currently supported format like ZIP or 7z will open on far more systems without extra software.

Will a new .lha file open on Windows without installing anything?
No. Windows has never included built-in LHA/LZH support, at any version, so a separate archiver has to be installed first, and even 7-Zip's standard build won't help without an add-on.

Does LHA compress better than ZIP or 7z?
Generally, no. LHA's compression windows top out at 64 KiB even in its most advanced method, which was reasonable for 1980s hardware but is small compared with the far larger windows modern formats like 7z's LZMA use on typical data today.

Can I password-protect a new LHA archive?
Not through the classic format itself — LHA/LZH was never built with the encryption features that current formats like 7z or AES-enabled ZIP include.

What actually opens an LHA file if I send someone one?
PeaZip lists native LHA/LZH support, and WinRAR can extract (though not create) it. Beyond those, options thin out quickly, since neither Windows nor standard 7-Zip includes any built-in support.