What is the RAR file format?
Files with the .rar extension contain data archives compressed with a proprietary algorithm. The format was first released in 1993 by Russian programmer Eugene Roshal and is currently developed and maintained by RARLAB alongside their WinRAR software. Two major format generations exist: RAR4 (dominant through the 2000s) and RAR5, introduced in 2013 with WinRAR 5.0, which brought stronger encryption and an updated archive structure.
.rar provides high compression and supports many additional functionalities, such as:
- Recovering data after storage errors, using
.revrecovery volume files - Splitting large archives into several smaller parts - continuation volumes use extensions like
.r00,.r01, and so on - AES-256 encryption of archive contents (RAR5; AES-128 in the older RAR4 format)
- CRC32 checksums and 256-bit BLAKE2sp hash verification for file integrity
Restrictions regarding RAR archives
RAR archives can be created only with the graphical WinRAR software on Microsoft Windows, or with the rar command-line program on other platforms. Third-party applications may also create .rar files if they hold a license agreement with RARLAB. Extraction is less restricted - RARLAB makes the unrar source code freely available, though it prohibits reverse-engineering. Because RAR4 and RAR5 use different structures, not all tools support both; older software may fail to open RAR5 files.
Security & safety
RISK: MEDIUMThe RAR format itself is safe, but archives are a classic malware-delivery wrapper: they hide the real file types until extracted and can sneak past basic filters, so a .rar from an untrusted source may contain executables or scripts - scan the contents before running anything. Two specific cautions: (1) RAR5 archives can be AES-256 encrypted and password-protected, which is also used to evade antivirus scanning, so be wary of password-protected RARs sent unsolicited; (2) self-extracting RAR .exe files run code by design - only open SFX archives from sources you trust. Extracting a normal RAR and inspecting its files first is the safe approach.
Format details
in a nutshellPrograms that open RAR files
Windows4 apps
WinRAR
Paid Double-click to open; Extract To. The only program that also CREATES .rar files (40-day trial, nags but keeps working). 
7-Zip
Open-source Right-click the .rar > 7-Zip > Extract Here. Free; extracts RAR (cannot create RAR). 
PeaZip
Open-source Open the .rar and Extract; free, supports RAR4/RAR5 extraction and split archives. 
NanaZip
Open-source Modern 7-Zip fork with Windows 11 context-menu integration; right-click > Extract. 
macOS2 apps
The Unarchiver
Free Set as default for .rar, then double-click to extract. Free on the Mac App Store; handles RAR and split archives.
Keka
Free Drag the .rar onto Keka to extract (RAR4 and RAR5). Free from the developer's site; the go-to Mac archiver. 
Linux3 apps
unar / The Unarchiver CLI
Open-source Run 'unar archive.rar' in a terminal; the free open-source unarchiver, handles RAR5.
unrar (RARLAB)
Free Run 'unrar x archive.rar'. RARLAB's official extractor; reads every RAR variant. (Extract only.)
Xarchiver / Ark / File Roller
Open-source GUI archive manager; open the .rar and Extract (needs unrar/unar backend installed). 
Android1 app
RAR (RARLAB)
Free Official RARLAB app; browse to the .rar, tick it, and tap Extract. Also handles ZIP/7z. Technical details
deep spec| Magic bytes | `52 61 72 21 1A 07` ("Rar!" + 0x1A 0x07) at file offset 0 |
| Version signature byte | 7th byte `00` = RAR 1.5-4.x; bytes `01 00` = RAR5 (introduced with WinRAR 5.0, 2013) |
| MIME type | `application/vnd.rar` |
| Compression algorithm | Proprietary; PPMd variant for text, LZSS-based for binary data; files share one compression dictionary in solid mode |
| Encryption | AES-128 CBC (RAR4) / AES-256 CBC with PBKDF2 key derivation (RAR5) |
| Integrity verification | CRC32 per file (RAR4); CRC32 or optional 256-bit BLAKE2sp hash per file (RAR5) |
| Multi-volume naming | Legacy: `.r00`, `.r01`, … ; modern: `.part1.rar`, `.part2.rar`, … (default in RAR5) |
| Recovery volumes | `.rev` files store parity data allowing reconstruction of missing volumes without re-downloading the entire set |
| Solid compression | All files share one compression dictionary - improves ratio significantly for many small, similar files |
| Self-extracting archives | WinRAR can produce `.exe` SFX archives with an embedded decompressor requiring no separate tool on Windows |
| Filename encoding | UTF-8 natively in RAR5; code-page-dependent in RAR4, which may garble names across different locales |
| Archive comments | Plain-text comments up to 64 KB can be embedded in the archive header |
| Header encryption | Optional feature that encrypts the file listing, hiding filenames until the correct password is supplied |
| License model | Proprietary creation requires WinRAR or a licensed SDK; `unrar` source available for extraction only - reverse-engineering prohibited |
| Released | 1993 (RAR 1.0); RAR4 format ~2002; RAR5 format 2013 (WinRAR 5.0) |
| Specification | www.rarlab.com |
RAR conversions
Community Q&A
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