Convert TAR.BZ2 to RAR Online (Tar's Open Header Meets a Closed Format)

What Sits Inside a .TAR.BZ2 Archive Before It Becomes a RAR

A .tar.bz2 file bundles files using tar's 512-byte-block header format — recording each file's name, size, permissions, and owner ahead of its data — and compresses that entire concatenated stream afterward with bzip2, working in blocks of up to 900 KB. Both halves of that structure are fully documented: tar's format has been standardized since POSIX.1-1988, and bzip2's Burrows-Wheeler-based algorithm has been openly published since Julian Seward's 1996 and 1997 releases. Anyone can, and many independent projects have, implemented either one from scratch using only public documentation.

RAR isn't built the same way. Its compression algorithm is proprietary to RARLAB, the company behind WinRAR, and has never been published as an open specification the way tar's or bzip2's have been. That gap in openness is the single most consequential difference this particular conversion actually crosses — more so than any specific technical detail about block sizes or dictionaries.

Why Only One Company's Software Can Actually Write This Format

The unRAR source code, which lets other software read and extract existing RAR archives, is freely licensed for that specific purpose — but that same license explicitly prohibits using it to build software that creates new RAR archives, which is the documented, legal reason mainstream tools like 7-Zip and PeaZip can open a RAR file but categorically cannot write one, on any platform, under any configuration. Converting a .tar.bz2 to RAR therefore always depends on WinRAR itself or RARLAB's own command-line rar tool, since they're the only software actually licensed to produce the format.

The tar-level details that matter inside a .tar.bz2 — long filenames handled through GNU tar's own extension or the PAX format, sparse files recorded through tar's documented sparse-format headers, Unix permission bits stored directly in every header — don't have a direct equivalent inside RAR's own container the way they do inside tar's. RAR stores its own per-file metadata natively, similar in spirit to 7Z, meaning any file that depended specifically on tar's extension mechanisms to preserve a long name or a sparse layout gets that metadata handled by RAR's own header format instead, once the conversion rebuilds the archive.

RAR's own current format, RAR 5.0, is also a genuinely different structure from the earlier RAR 4.x line, not just a version increment — it raised the maximum number of volumes a split archive can use from 255 to 65,535, and changed its internal block layout enough that some format-specific features, like certain filename-encryption options, aren't available when a tool builds an archive in the older format specifically for compatibility with software that hasn't been updated to expect RAR 5.0.

What Moving From TAR.BZ2 to RAR Gains and Costs

• Gain — self-healing recovery records: RAR 5.0's Reed-Solomon-based recovery record can repair a bounded amount of archive damage automatically, with no equivalent inside a plain bzip2 tarball.
• Gain — native per-file storage, no 256-character path limit: RAR's own header format doesn't inherit tar's classic filename-length ceiling, so long paths need no GNU or PAX extension to survive.
• Gain — filename encryption alongside content encryption: a password-protected RAR can hide the archive's file list itself, something tar and bzip2 together have no capability for at all.
• Lose — free, unrestricted creation rights: writing a RAR always depends on RARLAB's licensed software; a .tar.bz2 can be built by any of dozens of independent, free tools.
• Lose — tar's sparse-file space savings: a sparse file preserved efficiently through tar's own sparse-format headers typically expands to its full size once rebuilt inside RAR's container.
• Unchanged — the actual file content: what extracts out the other end is identical either way, aside from the sparse-file and metadata caveats specific to this pairing.

Who Can Build a RAR Versus Who Can Only Read One

WinRAR and RARLAB's command-line rar tool, available for Windows, macOS, and Linux, are the only software actually licensed to create RAR archives — WinRAR is free to evaluate but formally shareware once its trial period ends, though it keeps functioning afterward with a persistent reminder rather than a hard lockout. Extraction is available far more broadly: 7-Zip, PeaZip, The Unarchiver, and Windows 11's File Explorer (starting with the 24H2 update, via its libarchive-based archive support) can all open an existing RAR file without any licensing restriction, since the extraction-only unRAR code is freely distributable.

Tar and bzip2 sit at the opposite end of that spectrum entirely: both are preinstalled by default on essentially every Linux distribution and macOS, with no license, purchase, or evaluation period involved on either side of building or reading a .tar.bz2 file — a genuinely different distribution model from anything touching RAR's compression side.

Real Complaints Reported Converting Tar Archives Into RAR

A frequent complaint on forums involves someone opening a free tool like 7-Zip specifically to create a RAR archive and finding no option to do so anywhere in the interface — this isn't a missing setting to hunt for, but a direct consequence of RAR creation being legally restricted to RARLAB-licensed software; the documented resolution is installing WinRAR or RARLAB's own command-line tool specifically for that step.

A second recurring pattern involves a sparse virtual-machine or database image bundled efficiently inside the original .tar.bz2 through tar's sparse-format headers, then converted to RAR and found to take up considerably more disk space than expected — the explanation reported consistently is that RAR has no equivalent native mechanism for treating an arbitrary file as sparse before compressing it, so the space savings tar's format specifically provided simply don't carry over.

A third documented issue involves Unix permissions and ownership, which live directly in every tar header, not surviving a conversion to RAR consistently across platforms — RAR's own metadata handling for Unix-specific attributes varies depending on which platform and version of the software actually built the archive, unlike tar's format, where that information is simply always present regardless of the tool used.

A fourth pattern shows up around recovery records specifically: someone enables RAR's optional recovery-record protection on a converted archive expecting it to guard against any level of damage, then finds a badly corrupted file still can't be repaired — the Reed-Solomon recovery record is effective against a bounded amount of damage proportional to how much recovery data was actually allocated when the archive was built, not an unlimited guarantee, and the practical fix reported in these threads is choosing a larger recovery-record percentage for archives that genuinely can't be re-created from source.

TAR.BZ2 and RAR Compared Directly

Common Questions About Converting TAR.BZ2 Files to RAR

Why can't I make a RAR file with a free tool?
Because RAR's compression algorithm is proprietary, and the license covering the freely available unRAR extraction code specifically forbids using it to build software that creates RAR archives. Only WinRAR and RARLAB's own tools are licensed to do that.

Do sparse files stay compact after converting to RAR?
Usually not. Tar's sparse-file space savings depend on its own sparse-format headers, which RAR has no equivalent for, so a sparse file typically gets stored at its full expanded size in the new archive.

Can I open a RAR file for free even if I can't create one?
Yes. 7-Zip, PeaZip, The Unarchiver, and Windows 11's 24H2-and-later File Explorer can all extract existing RAR archives at no cost, since the extraction-only unRAR code is freely licensed.

Does RAR preserve Unix file permissions reliably?
Not as consistently as tar does. RAR's handling of Unix ownership and permission bits varies by platform and version, whereas tar always stores that information in its header regardless of which tool wrote it.

Does converting to RAR change the underlying files?
No. The extracted file content comes out identical either way, aside from the sparse-file and metadata caveats specific to moving out of tar's container.

Is RAR's compression better than bzip2's?
Results vary by content and settings, and there's no precise general comparison possible, since RAR's exact algorithm isn't published in the detail bzip2's openly documented method is.

Does the RAR 5.0 format differ meaningfully from RAR 4.x for this conversion?
Yes. RAR 5.0 raised the maximum split-archive volume count from 255 to 65,535 and changed its internal block layout, so some newer features like certain filename-encryption options aren't available if a tool is told to build the older RAR 4.x format specifically for compatibility.