The zstd CLI provides fast and flexible decompression capabilities with various output and validation options.
Basic Decompression
Standard Decompression
# Decompress a file
zstd -d file.txt.zst
# Output: file.txt
# Alternative syntax
zstd --decompress file.txt.zst
unzstd file.txt.zst
Decompress to stdout
# Write to stdout
zstd -dc file.txt.zst
zstd -d -c file.txt.zst
# Using symlinks
zstdcat file.txt.zst
zcat file.txt.zst
Specify Output File
# Decompress to specific file
zstd -d file.txt.zst -o output.txt
# Keep compressed file (default)
zstd -d -k file.txt.zst
# Remove compressed file after decompression
zstd -d --rm file.txt.zst
List File Details
# Display information about compressed file
zstd -l file.txt.zst
# Verbose information
zstd -lv file.txt.zst
- Original size
- Compressed size
- Compression ratio
- Checksum (if available)
Some fields may not be available depending on how the file was compressed (e.g., missing content size if compressed with --no-content-size).
Integrity Testing
Test Compressed Files
# Test file integrity without decompressing
zstd -t file.txt.zst
zstd --test file.txt.zst
# Test multiple files
zstd -t *.zst
zstd -d --stdout > /dev/null. Data is decompressed and checksummed but discarded. No files are created or removed.
Checksum Validation
# Validate checksums during decompression (default)
zstd -d file.txt.zst
# Ignore checksums
zstd -d --no-check file.txt.zst
Memory Limits
Set Memory Usage Limit
# Limit decompression memory to 256 MiB
zstd -d -M 256MiB file.txt.zst
# Limit to 128 MiB (default)
zstd -d -M 128MiB file.txt.zst
If a compressed file requires more memory than the limit allows, decompression will fail. This is particularly relevant for files compressed with high windowLog values or --long mode.
Large Window Sizes
For files compressed with windowLog > 27:
# Decompress with large window (from --long=30)
zstd -d --long=30 file.txt.zst
# Or specify memory directly
zstd -d --memory=1GiB file.txt.zst
Sparse Files
Sparse Mode
# Enable sparse file support (default for files)
zstd -d --sparse file.txt.zst
# Disable sparse mode
zstd -d --no-sparse file.txt.zst
# Force sparse mode for stdout
zstd -dc --sparse file.txt.zst
Sparse mode is enabled by default when output is a file and disabled when output is stdout. Sparse files save disk space and speed up decompression by reducing I/O for files with many zeros.
Pass-through Mode
Handle Uncompressed Files
# Pass through uncompressed files as-is
zstd -d --pass-through file.txt
# Force pass-through to stdout
zstd -df --pass-through file.txt
-f is set.
Recursive Decompression
Decompress Directories
# Decompress all .zst files in directory
zstd -d -r directory/
# Output to flat directory
zstd -d -r --output-dir-flat /output/dir input/
# Preserve directory structure
zstd -d -r --output-dir-mirror /output/dir input/
Multiple File Decompression
File Lists
# Decompress files from list
zstd -d --filelist files.txt
# Create file list
ls *.zst > files.txt
zstd -d --filelist files.txt
ls output, one file per line.
Wildcards
# Decompress multiple files
zstd -d *.zst
zstd -d file1.zst file2.zst file3.zst
Dictionary Decompression
Using Dictionaries
# Decompress with dictionary
zstd -d file.txt.zst -D dictionary
# Dictionary is required for files compressed with -D
zstd -d FILE.zst -D dictionaryName
Files compressed with a dictionary require that same dictionary for decompression. The decoder will verify the dictionary ID matches.
Memory-mapped Dictionaries
# Memory-map dictionary instead of loading it
zstd -d --mmap-dict -D large-dictionary file.txt.zst
# Disable memory mapping (default)
zstd -d --no-mmap-dict -D dictionary file.txt.zst
Progress and Output Control
Verbosity
# Verbose output
zstd -dv file.txt.zst
# Very verbose
zstd -dvv file.txt.zst
# Quiet mode (suppress warnings)
zstd -dq file.txt.zst
# Very quiet (suppress errors too)
zstd -dqq file.txt.zst
Progress Counter
# Force show progress
zstd -d --progress file.txt.zst
# Hide progress
zstd -d --no-progress file.txt.zst
Progress counter is shown by default for single file decompression. When output is mixed with progress text, use --no-progress.
Force Operations
Override Protections
# Force various operations
zstd -df file.txt.zst # Overwrite existing files
zstd -df file.txt.zst > output # Force stdout to terminal
-f flag:
- Allows overwriting existing files
- Enables output to stdout even if it’s a terminal
- Enables pass-through of unrecognized formats
- Operates on links and block devices
Concatenated Files
# Decompress concatenated .zst files
zstd -d concatenated.zst
.zst files concatenated together are decompressed as if they were a single file:
cat file1.zst file2.zst file3.zst > combined.zst
zstd -d combined.zst
# Outputs: combined (containing data from all three files)
Asynchronous I/O
# Use async I/O (default)
zstd -d --asyncio file.txt.zst
# Disable async I/O
zstd -d --no-asyncio file.txt.zst
# Automatically detects .zst format
zstd -d file.txt.zst
# Can also decompress gzip (if compiled with zlib)
zstd -d file.txt.gz
# And xz/lzma (if compiled with lzma)
zstd -d file.txt.xz
zstd -d file.txt.lzma
# And lz4 (if compiled with lz4)
zstd -d file.txt.lz4
Trace Logging
# Log tracing information
zstd -d --trace trace.log file.txt.zst