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Tech riderRev. 30 Sept 2026

UPX

Ch 067.0of 27 Executable Packers
  1. 1Runs onLinux, Mac, Windows
  2. 2CostsFree plan
  3. 3License modelperpetual
  4. 4Supported platformsWindows, macOS, Linux
  5. 5Binary formatsPE, ELF, Mach-O, COFF, DOS/COM, DOS/EXE, DOS/SYS, Atari/TOS
  6. 6Compression levelsadvanced
  7. 7Protection featuresNo
  8. 8Architecture supportmulti-architecture
8 lines stated Written from the maker's own pages: upx.github.io
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The UPX homepage

Overview

UPX is ranked #6 of 27 in executable packers on Specifiction. It runs on Linux, macOS, Windows. There is a free plan.

UPX plans and pricing

All plans
UPX Free Free software under GPL v2+; special license exception permits use with commercial programs upx.github.io · 30 Sept 2026

Compared on executable packers

Free plan
Yesupx.github.io
Supported platforms
Windows, macOS, Linuxupx.github.io
Binary formats
PE, ELF, Mach-O, COFF, DOS/COM, DOS/EXE, DOS/SYS, Atari/TOSupx.github.io
Compression levels
advancedupx.github.io
Protection features
Noupx.github.io
Architecture support
multi-architectureupx.github.io
License model
perpetualupx.github.io

Facts

Purpose
UPX is a portable executable packer and file compressor for several executable formats.upx.github.io · 30 Sept 2026
Compression
The project says UPX typically reduces program and DLL file sizes by around 50%–70%.upx.github.io · 30 Sept 2026
Runtime behavior
Compressed programs are self-contained and run as before with no runtime or memory penalty for most supported formats.upx.github.io · 30 Sept 2026
Supported executable formats
UPX supports formats including Windows programs and DLLs, macOS apps, and Linux executables.upx.github.io · 30 Sept 2026
Inspect and restore
UPX can list, test, and unpack executables, and internally maintains checksums of compressed and uncompressed files.upx.github.io · 30 Sept 2026
License
UPX is distributed with full source under GPL v2 or later, with a special exception allowing unmodified UPX to compress commercial programs.upx.github.io · 30 Sept 2026
Security handling
The project warns that UPX inherits the security context of files it handles and says to use it only on trusted files.github.com · 30 Sept 2026
Security limits
UPX describes itself as a packer and explicitly says it will not add protection or encryption features.github.com · 30 Sept 2026
Linux runtime tradeoff
The documentation says compressed Linux executables do not share RAM at runtime like file-mapped executables, so concurrent processes may need more RAM or swap.github.com · 30 Sept 2026
Linux temporary files
For its generic Linux format, UPX recreates a copy of the original file in /tmp before running it.github.com · 30 Sept 2026
Download platforms
The latest release page provides Linux and Windows binaries, DOS builds, and a source tarball; it says each build handles all supported executable formats.github.com · 30 Sept 2026
Support
The project asks users to report bugs through its GitHub issues page.github.com · 30 Sept 2026
Maker
The homepage says UPX is maintained by the UPX Team and credits Markus F.X.J. Oberhumer, László Molnár, and John F. Reiser.upx.github.io · 30 Sept 2026

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Where it ranks on Specifiction

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