TAR to 7Z Converter

What is TAR to 7Z Conversion?

Converting TAR to 7Z is the process of repacking an uncompressed archive container into a modern format with highly efficient compression. TAR (Tape Archive) appeared in 1979 as a Unix standard for combining many files into a single data stream. By itself, TAR does not compress data; it merely stores files together with their POSIX attributes inside a single container. 7Z is a format introduced by Igor Pavlov in 1999 alongside the 7-Zip archiver, using the LZMA2 algorithm with a dictionary of up to 1 GB and a solid compression mode.

The main motivation for converting TAR to 7Z is a radical reduction in size. An uncompressed TAR archive takes up the same space as the source files combined. After applying LZMA2, the volume can shrink by a factor of 5 to 10 for text data and source code. At the same time, 7Z lets you keep the entire file set in one container with password protection and integrity verification through checksums.

The conversion process reads the TAR structure, extracts each file while preserving names, paths, and timestamps, then builds a new 7Z container with LZMA2 applied. The files inside the archive remain byte for byte intact; only their storage method and compression change.

Technical Differences Between TAR and 7Z Formats

Algorithms and Storage Principles

TAR works as a pure container: files are written sequentially in 512 byte blocks, with a header before each file containing metadata (name, size, access rights, owner, timestamps). No compression is applied; every byte of the source file ends up in the archive unchanged. This makes TAR fast to create and extract but extremely inefficient in terms of size.

7Z uses the LZMA2 algorithm, an improved version of LZMA. The algorithm builds a data model, identifies repeating sequences at distances up to 1 GB, and encodes them with compact references. In solid mode, 7Z merges multiple files into a single stream before compression, which lets the algorithm find common patterns between files and achieve extreme compression ratios for uniform data.

Capability Comparison Table

Real Compression: From TAR to 7Z

Size ratios for typical working sets:

The compression effect peaks on text data, source code, databases, and logs. On already compressed files (JPEG, MP3, MP4, ZIP nested in TAR), the benefit is minimal because the entropy of such data is close to maximum.

When TAR to 7Z Conversion is Necessary

Long Term Archive Storage

Backups and archive copies are often kept for years and rarely opened. In such scenarios, compactness is critical:

• Project documentation archive - thousands of documents and spreadsheets can shrink 5-7 times, freeing space on NAS storage.
• Source code backups - for teams maintaining project history for decades, switching from TAR to 7Z saves terabytes of disk space.
• Mail and log archives - technical logs have huge redundancy, and LZMA2 compresses them extremely efficiently.

Transferring Large Volumes Over the Internet

When sending archives, size directly affects transfer time and traffic cost:

• Cloud storage with quotas - storage services often have volume limits, and a compact 7Z lets you fit more data.
• Distribution via FTP/SFTP - for servers with limited bandwidth, smaller size means faster delivery to recipients.
• Limited mobile traffic - when working from trips or on slow connections, 7Z saves tens of minutes of transfer time.

Cross Platform Exchange with Space Savings

TAR archives are historically tied to the Unix environment, but 7Z is recognized universally:

• Sending to colleagues on Windows - the 7-Zip archiver is widespread on Windows and opens 7Z instantly.
• Sharing across mixed teams - designers on macOS, developers on Linux, and managers on Windows receive a compact file that each can extract with familiar tools.
• Publishing distributions - by releasing programs in 7Z, developers save on hosting and download speeds for users.

Storing Virtual Machines and Disk Images

VMware, VirtualBox, and QEMU disk images packed in TAR consume enormous space. LZMA2 efficiently compresses sparse disk structures:

• VMDK and VDI images - can shrink 3-5 times due to large zero filled regions.
• Container snapshots - Docker images and LXC snapshots become more compact in 7Z.
• Vagrant box archives - prebuilt VM templates for distribution become noticeably smaller.

Conversion Process: What Happens to the Archive

Transformation Stages

1. Reading the TAR stream - 512 byte blocks are read sequentially, file headers are parsed, and contents are extracted. At this stage, the full directory hierarchy is restored.

2. Content analysis - the data type in the archive is determined to choose optimal LZMA2 parameters. For already compressed files, the store mode without compression is applied; for text, the maximum level is used.

3. Solid block formation - in solid mode, all files are merged into a single stream. This allows the algorithm to find repetitions between files and compress the set as a whole.

4. Applying LZMA2 - data is passed through the algorithm with dictionary settings (typically 64-256 MB for an optimal balance of speed and compression).

5. Writing the 7Z container - an archive header is built with the file list, sizes, and CRC-32 or CRC-64 checksums. The end of the archive contains a signature and index.

What is Preserved and What Changes

Preserved:

• File contents byte for byte
• Names and extensions with Unicode support
• Full folder and subfolder structure
• File modification timestamps
• Basic attributes (read, execute permissions)

Changed:

• Archive size (typically reduced 3-15 times)
• Storage method (solid block instead of sequential write)
• Checksums (CRC added per file)

May be lost or transformed:

• Exact Unix permissions (rwx for owner, group, others) - 7Z partially supports them through extensions
• Owner and group identifiers (uid, gid)
• Symbolic and hard links - preserved as regular files
• FIFO, sparse files, and Unix special devices

Comparing 7Z with Other Archive Formats

7Z vs ZIP

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

7Z wins in compression, ZIP in accessibility.

7Z vs TAR.XZ

TAR.XZ uses the same LZMA2 algorithm but in a different container.

7Z is more convenient for mixed teams, TAR.XZ for pure Unix tasks.

7Z vs RAR

RAR is a proprietary format by Eugene Roshal.

7Z remains the choice for free and open solutions.

7Z Compatibility and Support

Operating Systems

7Z requires installing an archiver, but support is broad:

• Windows - 7-Zip, WinRAR, Bandizip, PeaZip recognize 7Z. 7-Zip ships free with open source code.
• macOS - The Unarchiver, Keka, BetterZip open 7Z and integrate with Finder.
• Linux - the 7z, 7zz, 7zip utilities are available in standard repositories of most distributions (Ubuntu, Fedora, Arch, openSUSE).
• Android - ZArchiver, RAR, and 7Zipper read 7Z on smartphones and tablets.
• iOS - iZip, Documents by Readdle support 7Z on iPhone and iPad.

Development Tools

For automating work with 7Z in code:

Format Development History

7Z was created by Russian developer Igor Pavlov in 1999 along with the 7-Zip archiver. The specification is open, and the implementation is distributed under the GNU LGPL license.

Key milestones:

• 1999 - first 7-Zip release with basic LZMA support
• 2008 - LZMA2 introduced, optimized for multi threading
• 2010 - AES-256 encryption added with optional file name hiding
• 2015 - performance improvements on multi core processors
• 2022 - 7-Zip 22.00 release with ZSTD support and improved handling of large archives

Despite being young relative to ZIP, 7Z firmly occupies the niche of the format with the best compression.

Limitations and Alternatives

When Converting to 7Z is Not Optimal

• Archives of already compressed files - if TAR contains JPEG, MP4, MP3, the gain from LZMA2 is minimal at significant CPU cost.
• Scenarios requiring exact Unix attributes - for system backups with critical permissions and owners, TAR.XZ is better.
• Working on weak devices - LZMA2 extraction requires significant memory and CPU time, which is noticeable on older hardware.

Alternative Scenarios

If 7Z is not suitable for some reason:

• TAR to TAR.XZ - similar compression with full POSIX attribute preservation
• TAR to TAR.GZ - faster extraction, slightly worse compression, Unix standard
• TAR to TAR.BZ2 - middle ground between gz and xz, historic choice for source code
• TAR to ZIP - universal compatibility without installing software

For scenarios where archive size and subsequent distribution matter most, 7Z remains one of the best choices on the market.