Archives & Files · Error fix

Fix "gzip: stdin: not in gzip format"

gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error is not recoverable: exiting now

You asked gzip (often through tar -z) to decompress a file that does not start with the gzip signature. The file is something else with a .gz or .tar.gz name, most often a plain tar, an xz or bzip2 archive, a ZIP, or an HTML error page saved by a download.

Also appears as: gzip: backup.gz: not in gzip format · gzip: stdin: not in gzip format tar: This does not look like a tar archive · zlib.error: Error -3 while decompressing data: incorrect header check · gzip: stdin: decompression OK, trailing garbage ignored

Common causes

The download saved an HTML page (404, login, redirect) instead of the archive
The archive is an uncompressed tar named .tar.gz
It is compressed with xz, bzip2 or zstd rather than gzip
It is actually a ZIP file with the wrong extension
A web server or browser already decompressed a Content-Encoding: gzip download
FTP ASCII mode or a text editor altered the binary data

How to fix it

Check what the file is. Run file backup.tar.gz. A gzip file reports 'gzip compressed data'; other results like 'POSIX tar archive', 'XZ compressed data', 'Zip archive' or 'HTML document' tell you what to do next.
Let tar detect the compression. GNU tar detects compression on extract, so tar -xf backup.tar.gz works for gzip, bzip2, xz and plain tar. Only add -z when you are sure it is gzip.
Use the matching tool. Use tar -xJf for .tar.xz, tar -xjf for .tar.bz2, tar --zstd -xf for .tar.zst, and unzip for a Zip archive.
Re-download if it is HTML. Look inside with head -c 300 backup.tar.gz. If you see HTML, download again with curl -fL -o file URL and include any required authentication.
Re-transfer in binary mode. If the file reports as gzip on the server but not locally, the transfer changed it. Copy it again with scp, rsync or FTP binary mode and compare sha256sum.

Terminal

file backup.tar.gz
# gzip compressed data   -> tar -xzf backup.tar.gz
# POSIX tar archive      -> tar -xf backup.tar.gz
# XZ compressed data     -> tar -xJf backup.tar.gz
# Zip archive data       -> unzip backup.tar.gz
# HTML document          -> download it again with curl -fL

How to stop it happening again

Use curl -fL so error pages are not saved as archives
Name archives by their real compression (.tar, .tar.gz, .tar.xz, .zip)
Use tar -xf without a compression flag and let GNU tar detect it
Publish and verify checksums for downloadable archives

File2fix tools for this error

TAR/GZ ⇄ ZIP Converter →

Frequently asked questions

Why does tar say Child returned status 1?

tar ran gzip as a child process to decompress the file, gzip failed, and tar reports that failure. The real error is the gzip line above it.

The browser downloaded a .tar.gz that is already decompressed. Why?

Some servers send .tar.gz files with Content-Encoding: gzip, so the browser decompresses them while saving. The file is then a plain tar, so extract it with tar -xf.

Is 'trailing garbage ignored' a problem?

Usually not. gzip decompressed the valid data and ignored extra bytes at the end, often padding added during transfer. Check the extracted files, but the archive itself is normally fine.

Fix "gzip: stdin: not in gzip format"

Common causes

How to fix it

How to stop it happening again

File2fix tools for this error

Frequently asked questions

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