UPX

6.9easy start · #7 of 27
in Executable Packers

Free to practise onyes
Free trialnot on record
Well documentedyes
Runs where you workyes

Runs on Linux, Mac, Windows.

Visit site Alternatives

UPX is ranked #7 of 27 in executable packers on The Geeks Club. 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: Yes
Supported platforms: Windows, macOS, Linux
Binary formats: PE, ELF, Mach-O, COFF, DOS/COM, DOS/EXE, DOS/SYS, Atari/TOS
Compression levels: advanced
Protection features: No
Architecture support: multi-architecture
License model: perpetual

Best UPX alternatives

See all 12

Obsidian 0 of 4 in the starter kit Lesson 17.5 StarForce Reader 0 of 4 in the starter kit Lesson 27.4 Sentinel EMS 0 of 4 in the starter kit Lesson 37.3 Virbox Protector 0 of 4 in the starter kit Lesson 47.2 VMProtect 0 of 4 in the starter kit Lesson 57.0 Enigma Virtual Box 0 of 4 in the starter kit Lesson 66.9

The record

Purpose: UPX is a portable executable packer and file compressor for several executable formats.
Compression: The project says UPX typically reduces program and DLL file sizes by around 50%–70%.
Runtime behavior: Compressed programs are self-contained and run as before with no runtime or memory penalty for most supported formats.
Supported executable formats: UPX supports formats including Windows programs and DLLs, macOS apps, and Linux executables.
Inspect and restore: UPX can list, test, and unpack executables, and internally maintains checksums of compressed and uncompressed files.
License: UPX is distributed with full source under GPL v2 or later, with a special exception allowing unmodified UPX to compress commercial programs.
Security handling: The project warns that UPX inherits the security context of files it handles and says to use it only on trusted files.
Security limits: UPX describes itself as a packer and explicitly says it will not add protection or encryption features.
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.
Linux temporary files: For its generic Linux format, UPX recreates a copy of the original file in /tmp before running it.
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.
Support: The project asks users to report bugs through its GitHub issues page.
Maker: The homepage says UPX is maintained by the UPX Team and credits Markus F.X.J. Oberhumer, László Molnár, and John F. Reiser.
Price from: Free

Where it ranks on The Geeks Club

Best Executable Packers in 2026#7 of 27

Is UPX yours?

Claim it for free: prove the domain, then correct facts, plans and screenshots. An editor reviews every change.

Claim it free Promote UPX

Sources

upx.github.io· checked 30 Sept 2026
upx.github.io/upx-license.html· checked 30 Sept 2026
github.com/upx/upx· checked 30 Sept 2026
github.com/upx/upx/blob/devel/doc/upx-doc.html· checked 30 Sept 2026
github.com/upx/upx/releases/tag/v5.2.1· checked 30 Sept 2026