RAR occupies a strange position in the archive world. It's proprietary — only WinRAR can create RAR files, and the license costs money. It's outcompressed by 7z. It's less compatible than ZIP. And yet, RAR files are everywhere. You've received one in the last month, probably.
This persistence comes from two sources: the file-sharing community standardized on RAR decades ago (and habits die hard), and RAR has one genuinely unique feature that no other format matches — recovery records that can repair corrupted archives. That feature alone keeps RAR relevant for archival storage, even as 7z and Zstandard eat its lunch on compression.
Here's the full picture: what RAR does well, where it falls short, and when you should convert to an open format instead. Convert RAR to ZIP or RAR to 7Z right here.
Eugene Roshal and the RAR Format
RAR stands for Roshal ARchive, named after its creator Eugene Roshal. He developed the format and the WinRAR archiver in the early 1990s in Russia. Roshal's brother, Alexander Roshal, handles the business side through win.rar GmbH in Germany. The format is entirely proprietary — the compression algorithm is not publicly documented, and creating RAR archives requires licensed WinRAR software (or the rar command-line tool, which is also proprietary).
Extraction, however, is widely supported. Roshal released the UnRAR source code under a restrictive license (free to use and distribute, but you can't use it to create a RAR-compatible compressor). This is why 7-Zip, The Unarchiver, and most Linux tools can extract RAR files but not create them. It's a deliberate asymmetry that keeps WinRAR as the only creation tool while ensuring the format can be read anywhere.
RAR's Compression: Between ZIP and 7Z
RAR's compression sits between ZIP and 7z in efficiency. On a typical mixed dataset (documents, source code, images):
| Format | 1GB Mixed Files | 1GB Source Code | 1GB Log Files |
|---|---|---|---|
| ZIP (Deflate) | ~380 MB | ~120 MB | ~80 MB |
| RAR5 (Normal) | ~320 MB | ~80 MB | ~40 MB |
| 7z (LZMA2, solid) | ~280 MB | ~60 MB | ~18 MB |
RAR supports solid compression (same concept as 7z — treating all files as one stream), which is why it beats ZIP substantially on repetitive content. But LZMA2 (7z) uses larger dictionaries and more aggressive pattern matching, consistently outcompressing RAR's proprietary algorithm by 10-30%.
RAR's compression speed is moderate — faster than 7z at Ultra settings, slower than ZIP. Decompression is fast, comparable to 7z. The compression algorithm is proprietary and undocumented, which means it can't be independently verified for correctness or audited for security.
Recovery Records: RAR's Killer Feature
Recovery records are genuinely unique to RAR and genuinely useful. When creating an archive, you can add a recovery record — redundant error-correction data, typically 1-10% of the archive size. If the archive is later partially corrupted (bad disk sector, interrupted download, degrading optical media), WinRAR can use the recovery record to reconstruct the damaged portion.
How it works: RAR divides the archive into blocks and computes Reed-Solomon error-correction codes across those blocks. A 3% recovery record can repair up to 3% of continuous damage to the archive. A 10% recovery record can handle 10%. The recovery data is appended to the archive file, increasing its size by the specified percentage.
No other mainstream archive format offers this. If a ZIP, 7z, or TAR.GZ file gets a single corrupted byte in the compressed data stream, the entire archive (or the affected solid block, in 7z) may become unextractable. RAR with recovery records can survive moderate corruption.
This matters for: optical disc archival (CDs and DVDs degrade over time), network transfers over unreliable connections, long-term cold storage on hard drives with potential bad sectors, and any scenario where you can't guarantee perfect data integrity.
The alternative for other formats: use external PAR2 (Parchive) recovery files alongside your archive. PAR2 provides the same Reed-Solomon error correction for any file. But RAR's built-in recovery records are more convenient — a single file instead of an archive plus separate PAR2 files.
Multi-Volume RAR Archives and the Scene Standard
RAR's multi-volume support splits an archive into parts of a specified size (e.g., 50MB, 100MB, 200MB). This was historically important for fitting files onto floppy disks, CDs, and for uploading to file-sharing services with per-file size limits.
The "scene" — the community of groups that release pirated software, movies, and games — standardized on RAR multi-volume archives decades ago. Scene rules (yes, they have formal specification documents) mandate RAR format with specific volume sizes (15MB, 50MB, or other sizes depending on the release type). These rules were established in the late 1990s when split archives were necessary for distribution via FTP sites and Usenet.
The scene's adoption of RAR is why you encounter .rar, .r00, .r01 files when downloading content from less legitimate sources. It's also why RAR has such strong mind-share despite being technically inferior to 7z for compression. Inertia is powerful.
Today, multi-volume archives are mostly unnecessary — cloud storage and modern transfer protocols handle large files fine. But the convention persists, and if you receive multi-volume RAR files, you'll need WinRAR or 7-Zip to reassemble and extract them.
RAR5 vs RAR4: The Format Split
WinRAR 5.0 (2013) introduced RAR5, a major format revision. Key differences:
| Feature | RAR4 | RAR5 |
|---|---|---|
| Encryption | AES-128 | AES-256 |
| Hash algorithm | CRC32 | BLAKE2sp |
| Dictionary size | Up to 4MB | Up to 1GB |
| Max archive size | No practical limit | No practical limit |
| Recovery record format | Older Reed-Solomon | Improved Reed-Solomon |
| Filename encryption | Optional | Optional |
RAR5 is better in every dimension — stronger encryption, better hashing, larger dictionaries for improved compression. But RAR4 has broader tool support. Some older extraction tools (especially on Linux) handle RAR4 but choke on RAR5. If maximum compatibility matters, check that your recipient's tools support RAR5 before sending one. Or better yet, convert to ZIP.
The WinRAR "Trial" That Never Expires
WinRAR is commercial software with a 40-day free trial. After 40 days, it displays a nag screen on every launch asking you to buy a license. But it never stops working. No features are disabled. The nag screen has a close button, and the program continues functioning indefinitely.
This deliberate non-enforcement has become one of the internet's most enduring memes. Estimates suggest WinRAR has hundreds of millions of installs with a single-digit percentage license compliance rate. win.rar GmbH has never sued individual users. The business model relies on corporate licenses — companies pay because compliance departments require it.
The practical takeaway: WinRAR is effectively free for personal use, but if you're uncomfortable with the ethical gray area, just use 7-Zip. It's actually free (open source), handles RAR extraction, and creates better-compressed 7z archives. The only reason to buy WinRAR is if you specifically need to create RAR archives with recovery records.
Why You Should Convert RAR to ZIP or 7Z
If you receive a RAR file, extract it. If you're distributing files, don't use RAR. Here's why:
- Proprietary lock-in: Only WinRAR creates RAR files. If Roshal stops developing it, the format has no fallback implementation for compression. ZIP and 7z have multiple independent implementations.
- Worse compression than 7z: If you're choosing RAR for compression ratio, 7z does it better with LZMA2. The only RAR advantage over 7z is recovery records.
- Worse compatibility than ZIP: If you're choosing RAR for compatibility, ZIP is universally supported without any extra software. RAR requires the recipient to install something.
- Undocumented algorithm: RAR's compression algorithm has never been publicly documented. You're trusting proprietary binary code to handle your data correctly. Open formats can be independently verified.
Convert RAR to ZIP for sharing. Convert RAR to 7Z for archival. The only scenario where RAR is the best choice is when you need recovery records and don't want to manage separate PAR2 files.
RAR is a capable format with one genuinely unique feature (recovery records) weighed down by proprietary licensing and an undocumented algorithm. If you receive RAR files, extract them with 7-Zip (free). If you need recovery records for long-term archival, RAR is the most convenient option. For everything else, use ZIP or 7z.
Convert your RAR files to open formats: RAR to ZIP for sharing with anyone, RAR to 7Z for maximum compression, RAR to TAR.GZ for Unix environments. The conversion extracts the RAR and re-archives in the target format — your files are identical, just wrapped in an open container.