RAR to 7Z Converter

What is RAR to 7Z Conversion?

Converting RAR to 7Z means repacking archive contents from a proprietary container into an open format with a more modern compression algorithm. The files inside the archive are not modified, only the wrapper and the compression method change. RAR is an archive format developed by Eugene Roshal in 1993 in Russia and released by RarLab. It uses a combination of PPMd and LZSS algorithms, providing 10-30% better compression than ZIP, and supports recovery records for protection against corruption. 7Z is an open format created by Igor Pavlov in 1999, using the LZMA2 algorithm with a dictionary up to 1 GB and a solid compression mode that delivers even higher ratios on uniform data.

The main reason to convert RAR to 7Z is to keep maximum compression while moving to an open standard without licensing constraints. The 7Z specification is published and free to implement in any software, while creating RAR archives is closed and requires a license for the commercial RarLab software. Switching to 7Z provides independence from a single vendor and suitability for long term archiving according to open standard principles.

During conversion, the contents of the RAR are fully extracted into the original files, after which these files are packed into a new 7Z container. Names, folder structure, timestamps, and basic attributes are preserved. The size of the resulting 7Z archive is in most cases smaller than or comparable to RAR thanks to the larger dictionary and the solid mode, especially on collections of source code, text documents, and database dumps.

Technical Differences Between RAR and 7Z Formats

Compression Algorithms

RAR uses a proprietary algorithm based on LZSS (Lempel-Ziv-Storer-Szymanski) with PPMd (Prediction by Partial Matching) for text data. The dictionary size in RAR5 reaches 1 GB, bringing it close to LZMA2 capabilities. Additional filters detect x86 executable code, audio data, and delta tables, increasing efficiency on specific file types.

7Z applies the LZMA2 algorithm (Lempel-Ziv-Markov chain Algorithm 2) with an adaptive dictionary up to 1 GB and range coding. The key feature is the solid mode: many files are treated as one continuous data stream, allowing repetitions across different files to be found and achieving record breaking compression ratios on uniform collections.

Capability Comparison Table

Compression Ratio: Real Examples

Size ratios for typical data sets when comparing RAR and 7Z at maximum settings:

The advantage of 7Z over RAR appears on uniform and text data thanks to the solid mode and the more aggressive LZMA2 strategy. On already compressed data, both formats perform almost identically and the user will not see a significant difference.

When RAR to 7Z Conversion is Necessary

Switching to an Open Format

The openness of the 7Z specification provides strategic advantages:

• Vendor independence - 7Z is supported by thousands of utilities on all platforms, including built in tools in Linux distributions and package managers. Creating RAR archives requires licensed RarLab software, which limits automation.
• Long term data preservation - open standards are not at risk of being discontinued by a single company. 7Z archives will remain readable for decades.
• Compliance with corporate policies - many organizations require open formats only for document management and backups.
• Freedom of use in commercial products - developers can include 7Z support in their applications without licensing fees.

Achieving Maximum Compression

When you need to compress an archive more tightly than RAR allows:

• Source code archives - projects with many uniform files (tens of thousands of CSS, HTML, JS files) benefit the most from the 7Z solid mode.
• Database dumps - SQL exports with repeating table structures compress 12-20% more in 7Z.
• Log files - server journals, application logs, and system logs achieve better compression due to high entropy redundancy.
• Documentation collections - bundles of manuals, technical specifications, and scientific articles in PDF and DOCX often contain repeating templates.

Preparing for Publication in Open Repositories

Distribution scenarios through open channels:

• Free software mirrors - SourceForge, GNU FTP, Linux distribution mirrors mostly accept open formats.
• Wayback Machine archives - the Internet Archive project recommends open containers for long term preservation.
• Scientific databases - Zenodo, Figshare, Dataverse require open formats for research reproducibility.
• Government open data - state open data portals often require publication in formats not tied to specific vendors.

Unifying Archive Storage

When 7Z is already used as a standard in your infrastructure:

• Corporate retention policies - moving all archives to a single format simplifies audit, inventory, and automation.
• Backup systems - many enterprise solutions natively work with 7Z and do not require RarLab installation.
• CI/CD pipelines - build systems use 7Z for packaging build artifacts thanks to open libraries.

Conversion Process: What Happens to the Archive

Transformation Stages

1. Reading the RAR header - the format version (RAR4 or RAR5), the file list, the compression methods of each block, the presence of encryption, and the recovery records are analyzed.

2. LZSS/PPMd decompression - archive contents are decoded into the original files. For password protected archives, a password is required. If the archive is corrupted but contains recovery records, recovery is attempted.

3. Restoring file structure - files are temporarily placed in the original folder hierarchy with timestamps and attributes preserved.

4. Solid block analysis - files are grouped for solid compression based on type similarity: text together, binary separately, media files without compression.

5. Applying LZMA2 - data is processed by the algorithm with an adaptive dictionary size. For large archives, the dictionary is automatically increased to the optimal value.

6. Finalizing the 7Z container - a header is generated with structure description, file metadata, CRC-32 checksums, and optional encryption settings.

What is Preserved and What Changes

Preserved:

• File names and extensions (including Unicode characters)
• Folder and subfolder structure of any depth
• File contents (byte for byte)
• Modification timestamps
• Basic file system attributes

Changed:

• Archive size (usually reduced by 5-20% on text data)
• Compression algorithm and storage method
• Checksums (CRC-32 in 7Z instead of BLAKE2 in RAR5)
• Internal structure - 7Z solid blocks instead of separate RAR file compression

May be lost:

• Recovery records from RAR - 7Z has no equivalent mechanism
• Extended RAR comments (limited 7Z support)
• Alternate NTFS data streams

Comparing 7Z with Other Archive Formats

7Z vs ZIP

ZIP is a universal format with native support in all operating systems.

7Z wins over ZIP in compression, ZIP wins in compatibility.

7Z vs TAR.XZ

TAR.XZ combines the Unix TAR container with the XZ algorithm (based on LZMA2).

Compression ratios are roughly equal, the choice depends on the target environment.

7Z vs Modern Formats (Zstandard)

Zstandard is a Facebook compression algorithm focused on speed.

• Speed - Zstandard is 3-5 times faster at comparable compression
• Compression - 7Z achieves a higher ratio at maximum settings
• Adoption - 7Z is supported by a wider range of utilities

7Z remains the choice for tasks where maximum compression matters more than speed.

7Z Compatibility and Support

Operating Systems

Support for 7Z is available on all major platforms through free applications:

• Windows - the 7-Zip program is the de facto standard for extracting and creating 7Z archives. PeaZip, Bandizip, and NanaZip from the Microsoft Store are also supported.
• macOS - The Unarchiver, Keka, and BetterZip extract 7Z by double click and through the Finder context menu.
• Linux - the 7z, 7za, and 7zr commands are available in the standard repositories of all popular distributions and install with one package manager command.
• iOS and iPadOS - iZip, Documents by Readdle, and Zip Browser apps work with 7Z.
• Android - ZArchiver, RAR by RarLab, and built in file managers from some manufacturers support 7Z.
• Chrome OS - through the Linux subsystem, standard 7z utilities are available.

Programming Languages

7Z support is built in or available through libraries in all popular languages:

This allows automating creation and processing of 7Z archives in scripts and server applications.

Format History

The 7Z format was introduced by Igor Pavlov in 1999 along with the 7-Zip program. From the very beginning, the specification has been published openly, and the LZMA SDK source code is distributed in the public domain.

Key development milestones:

• 1999 - the first 7-Zip release and the 7Z format
• 2001 - LZMA stabilization as the main compression method
• 2009 - release of LZMA2 with multi threaded compression support
• 2016 - 7Z became the standard for open source software archives
• 2018-2024 - regular 7-Zip updates improving performance and security

Over a quarter century, 7Z has become the main competitor to RAR in the high compression archive niche and the only widely adopted open format of this class.

Limitations and Alternatives

When Converting to 7Z is Not Optimal

• Recipients without specialized software - if the recipient is not ready to install 7-Zip or an equivalent, ZIP is a better choice as it opens natively in all operating systems.
• Archives with critical recovery records - 7Z has no analogue of RAR recovery records, so for physical media with corruption risk RAR may be more reliable.
• Already compressed data - if the archive contains JPG, MP4, MP3, switching to 7Z will not yield noticeable space savings.

Alternative Scenarios

If different trade offs are needed:

• RAR to ZIP - universal compatibility for wide distribution
• RAR to TAR.XZ - for Linux environments with POSIX attribute support
• RAR to TAR.GZ - the standard for source code distribution in the Unix community

For long term archiving with a focus on standard openness and maximum compression, 7Z remains the optimal choice.