TGZ to TAR Converter

What is TGZ to TAR Conversion?

Converting TGZ to TAR means stripping the GZIP compression layer from the archive and obtaining a clean TAR container. The files inside are preserved fully unchanged byte for byte, as is the UNIX tarball structure itself: 512 byte records, headers with metadata, data blocks. The only thing that changes is that the archive is no longer compressed by the DEFLATE algorithm. TGZ (TAR + GZIP) is a composite format: an inner TAR container wrapped in an outer GZIP layer. The .tgz and .tar.gz extensions denote the same thing. TAR (Tape ARchive) appeared in UNIX in 1979 as a format for sequentially writing data to magnetic tape and over decades became a universal container for grouping files while preserving POSIX attributes.

The main reason for stripping GZIP compression is to gain the ability to work with archive contents without the limitations of streaming compression. A clean TAR can be opened by file managers on any system, files can be added or removed inside without full reassembly, other compression algorithms (BZIP2, XZ, ZSTD) can be applied, the archive can be indexed and verified byte by byte. TGZ does not allow any of this without full extraction due to its solid compression.

During conversion, the archive goes through a single step: decoding DEFLATE back into the original TAR stream. No changes are made to the file composition or directory structure. The size of the resulting TAR grows because the compression layer is removed, but in exchange the archive becomes "transparent" for all TAR tools.

Technical Differences Between TGZ and TAR Formats

Format Structure

TGZ is a two layer construction. The inner layer is a standard TAR archive consisting of a sequence of records: a 512 byte header plus file data padded to a multiple of 512 bytes. The outer layer is GZIP, wrapping the entire TAR stream in a compressed container with its own header (magic bytes 1f 8b), flags, and CRC-32 checksum. A .tgz file is always read linearly from start to end.

TAR is a single level container without compression. Each record is an ustar header (512 bytes) followed by file bytes. The end of the archive is two empty 512 byte blocks. TAR stores full UNIX attributes: owner (name and UID), group (name and GID), access permissions in octal form, timestamps in Unix time, file type (regular, directory, symbolic link, FIFO, device).

Capability Comparison Table

File Sizes: Real Examples

Size ratios for typical data sets:

The 1-3% growth in TAR relative to source files is due to record header overhead and block alignment. For media files and other already compressed formats, TGZ is practically indistinguishable from TAR in size.

When TGZ to TAR Conversion is Necessary

Modifying Archive Contents

A clean TAR allows working with contents without full extraction and recompression:

• Adding new files - utilities can append records to the end of a TAR archive without unpacking everything.
• Removing outdated files - command line tools or specialized programs can cut out specific records.
• Replacing individual files - updating configuration files or documents within the archive.
• Merging multiple archives - concatenating TAR files with subsequent defragmentation.

Applying Different Compression

Once a clean TAR is obtained, it can be repacked with another compression method:

• TAR to XZ - get better compression than GZIP, 10-30% tighter through LZMA2.
• TAR to BZ2 - switch to the BWT algorithm for better compression of text data.
• TAR to ZSTD - modern algorithm with high speed and compression comparable to XZ.
• TAR to LZ4 - ultra fast compression for frequent access.

Direct Access to Individual Files

In a clean TAR, an offset index can be built and files accessed without sequential reading:

• Document collections - extracting a specific PDF from thousands stored.
• Image sets - access to one image from millions in stock photo archives.
• Time stamped logs - extracting records for a specific day from a yearly archive.

Transfer Through Systems Without GZIP Support

Some embedded systems and older UNIX environments only handle plain TAR:

• Embedded devices - routers, IoT gateways with limited software.
• Minimal Docker and LXC images - base containers without GZIP utilities.
• Bootable ISO images - distributions using TAR as an intermediate format.

Integrity Control and Audit

A clean TAR is convenient for content audit:

• Checksum verification - SHA-256 of each file inside can be computed without unpacking to the file system.
• Antivirus scanning - scanners work more efficiently with a transparent TAR stream.
• Digital signing - easier to sign a specific TAR without dependence on the GZIP wrapper.

Conversion Process

Transformation Stages

1. Reading the GZIP header - magic bytes are checked, compression method (typically DEFLATE for GZIP) is determined, flags are parsed (presence of original file name, comment, extra fields).

2. Decoding DEFLATE - the algorithm reconstructs the original data stream from the compressed one: inverse LZ77 transformation (restoring repetitions from references) and Huffman codes (converting prefix codes to original bytes) are applied.

3. Checksum verification - GZIP contains a CRC-32 of the original uncompressed data. A mismatch indicates archive corruption.

4. Writing the TAR stream - the restored bytes are saved as a .tar file. This is the original TAR container that was compressed inside TGZ.

5. Finalization - the file is closed, file system metadata (name, timestamps) is set according to the OS.

What is Preserved and What Changes

Fully preserved:

• All files and directories within the archive (byte for byte)
• POSIX attributes (permissions, owner, group)
• Modification, access, and creation timestamps
• Symbolic and hard links
• Special file types (FIFO, devices)
• Extended attributes in PAX format

Changed:

• File size on disk (grows back to original uncompressed size)
• Extension (.tgz/.tar.gz to .tar)
• Single file extraction capability (becomes direct)

Nothing in the contents changes - TGZ to TAR conversion is absolutely lossless in archive composition.

Comparing TAR with Other Formats

TAR vs ZIP

ZIP is a universal format with built in compression; TAR is a clean container.

TAR is preferable in UNIX environments where attributes matter and built in compression is not required.

TAR vs CPIO

CPIO is another UNIX archiving format, an alternative to TAR.

TAR dominates general use; CPIO remains in specific niches.

TAR vs ISO

ISO 9660 is an optical disk image format.

TAR is for archiving, ISO is for disk images and installation media.

TAR Compatibility and Support

Operating Systems

TAR is one of the most supported formats in the UNIX family:

• Linux - the tar command is present in every distribution out of the box. GUI archivers (File Roller, Ark, Engrampa) open TAR with a double click.
• macOS - the tar command is part of the standard installation. Archive Utility extracts TAR through Finder.
• FreeBSD, OpenBSD, NetBSD - tar is in the base system.
• Solaris, AIX, HP-UX - tar is part of the standard UNIX utilities set.
• Windows - the tar command is built into Windows 10 (build 17063+) and Windows 11. GUI programs 7-Zip, WinRAR, PeaZip open TAR.
• Android and iOS - file managers with archive support work with TAR.

Programming Languages

Standard libraries of most languages include TAR support:

Format History

• 1979 - first tar implementation for UNIX version 7.
• 1988 - POSIX standardization as ustar (Uniform Standard Tape ARchive).
• 1992 - GNU tar extension with long name support through special records.
• 2001 - PAX standard (POSIX Archive Interchange) with extended attributes.
• Present day - TAR remains the dominant archive container in the UNIX world and serves as the foundation for TAR.GZ, TAR.BZ2, TAR.XZ, TAR.ZST.

Limitations and Alternatives

When Converting to TAR is Not Optimal

• Limited disk space - clean TAR takes up more space, which is critical with constrained resources.
• Transfer over slow channels - size is larger than TGZ, transfer time will increase.
• Long term storage - compressed formats are preferable for archival purposes.

Alternative Scenarios

• TGZ to TAR.XZ - get better compression while staying in the TAR family.
• TGZ to TAR.BZ2 - medium strength compression with strong Linux support.
• TGZ to TAR.ZST - modern ZSTD algorithm: fast extraction and good compression.

Conversion to plain TAR is optimal as an intermediate step: get a container, modify contents, apply new compression. For final storage or transfer a compressed form is usually chosen.