A proprietary archive file format with advanced compression and recovery features
RAR (Roshal Archive) is a proprietary file format for data compression and archiving, developed by Russian software engineer Eugene Roshal. First released in 1993, RAR has become one of the most popular archive formats, alongside ZIP, due to its superior compression efficiency and additional features.
Unlike some open archive formats, RAR is proprietary, with its compression algorithm remaining closed-source. While the decompression code has been made available through the free UnRAR library, creating RAR archives requires licensed software, most commonly WinRAR. This commercial aspect hasn't hindered RAR's popularity, as the format offers several advantages over alternatives, including better compression ratios, built-in error recovery, and advanced encryption.
RAR archives can span multiple files (volumes), making them suitable for splitting large archives across multiple storage media or for more manageable file transfers. The format also supports solid compression, which can significantly improve compression ratios for collections of similar files by treating them as a continuous data stream rather than compressing each file individually.
RAR uses a proprietary compression algorithm that often achieves better compression ratios than standard ZIP, especially when archiving similar file types together using the "solid archive" feature. The format has evolved through several versions, with RAR 5.0 (introduced in 2013) bringing significant improvements in compression efficiency, recovery record robustness, and encryption strength. RAR archives consist of a series of blocks that contain file data and metadata, enabling features like comments, error recovery information, and authentication data to be embedded within the archive.
RAR's superior compression and multi-volume capabilities make it ideal for distributing large files or collections, especially over networks with limited bandwidth. Software developers, media distributors, and content creators often use RAR to compress large applications, video collections, or game installations before distribution. The format's ability to split archives into manageable chunks (volumes) allows for easier transfers over networks or storage on limited-capacity media, while the solid compression feature provides better compression rates for collections of similar files.
RAR's strong encryption options make it suitable for secure storage of sensitive information. Businesses and individuals use RAR archives with AES-256 encryption to securely store financial records, personal documents, or confidential business information. The format's ability to both compress and encrypt in a single operation streamlines the process of securing data. Additionally, RAR allows for encryption of file names within the archive, providing an extra layer of privacy by concealing not just the contents but also the identity of the files being stored.
The built-in recovery record feature makes RAR valuable for creating resilient backups of important data. IT professionals and data managers incorporate RAR archives into backup strategies when data integrity is particularly important. By adding recovery records (typically 1-5% of the archive size), RAR enables repair of moderately damaged archives. For critical data, RAR's recovery volumes feature provides even greater protection, allowing for reconstruction of archives even when portions are completely lost or corrupted.
RAR is widely used in file-sharing communities due to its compression efficiency and multi-part capabilities. The format allows large content to be divided into smaller parts for easier uploading, downloading, and management. Additionally, RAR's comment feature enables distributors to include important information about the contents, installation instructions, or copyright notices directly within the archive. The ability to include checksums helps recipients verify they've received uncorrupted data, particularly important in informal sharing scenarios without guaranteed delivery mechanisms.
RAR's solid compression feature makes it particularly effective for archiving collections of similar files. Libraries, researchers, and data collectors use RAR to archive document collections, research data, or media libraries where many files share similar characteristics. By treating multiple files as a continuous data stream during compression, RAR can identify redundancies across file boundaries, achieving significantly better compression than file-by-file approaches. This makes RAR especially valuable for long-term storage of large collections where storage efficiency is important.
RAR has varying levels of native support across operating systems:
Various applications can work with RAR files:
Developers can work with RAR files using these libraries:
Different RAR versions have compatibility considerations:
| Feature | RAR | ZIP | 7Z | TAR.GZ | ISO |
|---|---|---|---|---|---|
| Compression Ratio | |||||
| Compression Speed | |||||
| Error Recovery | |||||
| Cross-Platform Support | |||||
| Security Features | |||||
| Open Standard | |||||
| Native OS Support |
RAR excels in compression efficiency and error recovery features but falls short in openness and native OS support. ZIP offers the best compatibility and native support but with less efficient compression. 7Z provides excellent compression ratios and feature set but requires third-party software. TAR.GZ combines good compression with Unix integration but lacks advanced features. ISO is specialized for disc images rather than general compression.
Converting RAR to ZIP is essentially a two-step process: extract the RAR archive, then compress the extracted files into a new ZIP archive. This can be done using tools like 7-Zip, WinRAR, or WinZip that support both formats. Keep in mind that ZIP typically achieves less compression than RAR, so the resulting ZIP file may be larger. For optimal results, adjust the ZIP compression level (usually a scale from "Store" to "Ultra") based on your needs for speed versus file size. Also consider whether special RAR features like solid compression or recovery records have meaningful ZIP equivalents.
Converting to 7Z can provide comparable or better compression than the original RAR. Use 7-Zip software for this conversion, which can extract RAR and create highly optimized 7Z archives. For the best compression, use LZMA2 compression with a dictionary size appropriate to your system's memory (larger dictionaries provide better compression but require more RAM). Like RAR, 7Z supports solid compression, which works well for similar file collections. 7Z also offers encryption options comparable to RAR's, making it a good choice when security is important.
Converting RAR to TAR or compressed variants (TAR.GZ, TAR.BZ2) is useful when working in Unix/Linux environments. The conversion process requires extracting the RAR contents first, then using tar command with appropriate compression flags (e.g., -z for gzip, -j for bzip2). On Windows, tools like 7-Zip can create TAR archives. TAR itself doesn't provide compression, so using a compressed variant is recommended. TAR.GZ offers good compression speed but less efficiency than RAR, while TAR.BZ2 provides better compression at the cost of speed.
When converting multi-volume (split) RAR archives, ensure all parts are available and in the correct order before attempting conversion. Most extraction tools can handle proper reassembly when all volume files are present in the same directory. Typically, you'll only need to open or extract the first volume file (e.g., filename.part1.rar or filename.r01), and the software will automatically process the remaining volumes. After extraction, create your new archive format from the complete extracted contents.
When converting between archive formats, be aware that different formats handle file metadata like permissions, ownership, and timestamps differently. ZIP has limited support for preserving Unix permissions compared to formats like TAR. If maintaining exact file permissions is critical, consider using TAR-based formats for Unix/Linux systems or test the conversion process with sample files to verify that essential attributes are preserved. Some archiving tools offer specific options to preserve extended attributes during conversion.
When converting encrypted RAR archives, you'll need the password to extract the contents before creating a new archive. The security of your converted archive depends on the encryption capabilities of the target format. ZIP offers password protection but uses weaker encryption than modern RAR. 7Z provides AES-256 encryption comparable to RAR5. If security is important, verify the encryption methods available in your target format and consider whether additional security measures (like separate encryption tools) might be needed.