RAR File — What It Is, Who Controls It, and What RAR5 Actually Changed
A proprietary archive format one company still owns outright, with a 2013 rewrite that changed the encryption math, the recovery-record structure, and the size limits underneath the familiar .rar extension.
- Add a file Choose or drop it here
- Pick the format Change it whenever needed
- Download the result After conversion completes
One Programmer's 1993 Format, Still Owned by the Same Company Today
RAR was created by Eugene Roshal in 1993 (the name stands for Roshal Archive) and remains a proprietary format owned and controlled today by RARLAB, the company behind WinRAR. Unlike ZIP, whose PKWARE-published APPNOTE.TXT specification anyone can implement freely, RAR's internal compression algorithm and encoding routines are not published as an open standard, and RARLAB licenses them out only in a limited way — through the separate unRAR source code, which exists purely for reading and extracting existing RAR archives, not creating new ones.
That licensing split has one very concrete consequence: WinRAR and RARLAB's own command-line rar tool are the only programs that can legally create a genuine .rar file. Free tools such as 7-Zip and PeaZip, and the open-source unrar utility, can all open and extract RAR archives using the licensed unRAR code, but none of them can produce one, because the unRAR license explicitly states that its source may not be used to develop a RAR-compatible archiver capable of creating new archives.
The only documented exception is uncompressed RAR creation, which some third-party tools attempt to support in a limited way, but even that carries real legal ambiguity, since the license was written around extraction, not creation, in any form. The practical takeaway for anyone needing to actually produce a .rar file is the same regardless of which website or utility promises otherwise: WinRAR or RARLAB's own rar.exe is genuinely the only fully legitimate route.
RAR5's 2013 Rewrite Changed the Encryption Math, Not Just the Version Number
RAR5 became the default archive format starting with WinRAR 5.0 in 2013, and it's a genuinely different design underneath the same extension, not a cosmetic update. RAR4 encrypts with AES-128 using a custom key-derivation approach, while RAR5 switched to AES-256 with keys generated through a proper PBKDF2 function running 131,072 rounds of SHA-256 — a specific, documented iteration count chosen to make brute-forcing a password meaningfully slower than RAR4's older key derivation allowed. RAR5 also stores a 12-byte password-verification value in its header alongside the salt and initialization vector, letting software check a guessed password quickly without decrypting the whole archive first.
Filename handling changed too: RAR4 always shows the list of filenames inside an archive, even when the file contents are encrypted, while RAR5 can optionally encrypt the filenames themselves — when that option is turned on, the archive's file list stays hidden until the correct password is entered, unlike RAR4's behavior of always revealing what's inside regardless of encryption.
The compression dictionary grew substantially as well: RAR5 supports a dictionary size up to 4 GB, compared with older RAR4 limits, and larger dictionaries generally let the algorithm find repeated patterns across a wider span of the input data, which is one reason RAR5 archives often come out smaller than the equivalent RAR4 archive of the same files.
None of this is a minor patch version — it's a full container-format change, which is exactly why software built to read RAR4 archives can't automatically read RAR5 ones without an update. WinRAR itself still supports creating RAR4-format archives when explicitly selected in its archive-options dialog, precisely because that older, more widely supported version remains necessary for compatibility with software and devices that predate the 2013 switch.
What Owning a RAR Archive Gets You and What It Costs
- Gain — a Reed-Solomon recovery record: WinRAR can embed error-correction data that its Repair function uses to rebuild a damaged archive; RAR5's version drops the older 512-byte sector structure and can size the record as any percentage of the archive, up to matching the archive's own size.
- Gain — solid archiving: treating every file as one continuous data stream instead of compressing file-by-file usually shrinks a folder of many small, similar files further than compressing each one separately.
- Lose — instant single-file extraction from a solid archive: pulling one file out of a solid RAR requires decompressing everything that came before it in the stream.
- Lose — free-of-charge creation: WinRAR is shareware; it keeps functioning past its 40-day trial but displays a licensing reminder on every launch afterward.
- Gain — stronger password protection under RAR5: AES-256 with 131,072 rounds of PBKDF2-SHA256 key derivation is substantially harder to brute-force than RAR4's older AES-128 scheme.
- Lose — guaranteed compatibility with very old RAR-reading software: tools built before 2013 sometimes can't parse the newer RAR5 container at all.
The Volume-Naming Scheme WinRAR Switched to and Why
Splitting a RAR archive across multiple files uses one of two naming schemes, and which one is available depends on the format version. Older RAR4-format archives can use an extension-based scheme where the first volume keeps the .rar extension and later ones are numbered .r00, .r01, up through .r99, using WinRAR's -vn switch. Starting with WinRAR 3.0, the default scheme changed to volname.part001.rar, volname.part002.rar, and so on — and RAR5 archives specifically do not support the older .r00-style naming at all, only the newer part-numbered scheme.
On Linux, this proprietary status shows up as a specific packaging split: Debian, for instance, ships unrar-nonfree in its non-free repository section rather than main, precisely because the official unRAR code's license terms (permitting extraction but barring RAR-compatible archiver development) conflict with Debian's free-software policy, while a separate unrar-free package built on a GPL-compatible library exists but doesn't support the older RAR3 format.
That extension-based scheme is also why it's capped at .r99: it only has two numeric digits to work with after the initial .rar volume, whereas the part-numbered scheme WinRAR moved to by default doesn't share that specific ceiling, since RAR5 requires it for every split archive regardless of how many volumes are involved.
The Documented Complaints That Keep Coming Back Around RAR
A frequent, documented question is why a .rar file downloaded on a Mac or phone won't open — the device usually isn't broken; neither macOS's Archive Utility nor most mobile operating systems bundle any RAR support by default, since RARLAB doesn't give away the format's compression code for free the way ZIP's algorithm is freely implementable. A separate app like The Unarchiver or Keka resolves this on macOS specifically.
A second recurring complaint is the WinRAR trial nag screen reappearing on every launch after 40 days, confusing people who assumed the software was fully free since it never stops actually working — RARLAB's own terms describe this as intentional: WinRAR remains usable indefinitely, but a license is technically required past the trial, and the reminder screen is the enforcement mechanism, not a malfunction.
A third pattern traces to the RAR4-to-RAR5 transition specifically: archives built with any current WinRAR default to RAR5, and RAR-reading software or embedded devices built before 2013 sometimes can't parse that newer container, reporting the file as unreadable even when nothing is actually damaged — switching WinRAR's format option back to RAR4 when creating the archive is the documented workaround for that specific compatibility gap.
RAR4 and RAR5 Measured Against Each Other Directly
| Feature | RAR4 (pre-2013) | RAR5 (2013+, current default) |
|---|---|---|
| Encryption | AES-128, custom key derivation | AES-256, PBKDF2-SHA256, 131,072 rounds |
| Filename encryption | Not available; names always visible | Optional; can hide the file list too |
| Recovery record structure | 512-byte sectors, capped near 256 MB useful size | Percent-of-archive size, no fixed sector cap |
| Volume naming | .rar, .r00, .r01... or .part001.rar | .part001.rar only |
| Compression dictionary | Smaller maximum | Up to 4 GB |
| Who can legally create it | WinRAR / rar.exe only | WinRAR / rar.exe only |
Common Questions About What a RAR File Actually Is
Who actually owns the RAR format?
RARLAB, the company behind WinRAR, founded around Eugene Roshal's original 1993 design — it remains proprietary rather than an openly published standard like ZIP.
Is RAR5 just a version number bump from RAR4?
No. RAR5 changed the encryption from AES-128 with a custom key derivation to AES-256 with PBKDF2-SHA256 at 131,072 rounds, restructured the recovery record, dropped the older .r00-style volume naming, and raised the maximum compression dictionary size.
Can any free program actually create a RAR file?
No. The unRAR source code that 7-Zip, PeaZip, and unrar rely on is licensed for extraction only; its terms explicitly forbid using it to build a RAR-compatible archiver that creates new archives.
What does a RAR recovery record actually protect against?
Physical or transmission damage to the archive file itself — WinRAR's Repair function can use the embedded Reed-Solomon data to rebuild missing or corrupted bytes, up to roughly the size of the recovery record that was added.
Why does Linux ship a separate "nonfree" package for RAR support?
Because the official unRAR code's license, while free to use for extraction, restricts redistribution and modification in ways that conflict with strict free-software policies like Debian's, so it gets placed in a non-free repository section instead of the main one.