UPX

At a glance

• Editor score
  8.9 / 10
• Pricing
  Free plan
• Best for
  Free cross-platform compression
• Free plan
  Yes
• Paid from
  Free
• Protection features
  No
• Facts checked
  20 Sep 2026

• Where it wins

  • Supports Windows, macOS, Linux, and multiple executable formats
  • Offers compression levels 1–9, --best, and multiple methods
  • Includes decompression, integrity checks, checksums, and size reporting

• Where it doesn't

  • Command-line operation may require technical familiarity
  • Provides no verified protection features
  • Compressed commercial distribution has special license conditions

Our verdict on UPX

UPX is a free, portable, open-source command-line packer for compressing executable programs, DLLs, libraries, and other supported binaries. It supports Windows, macOS, and Linux, with coverage for formats including PE, ELF, Mach-O, COFF, DOS, and Atari/TOS. The tool is suited to developers, release engineers, and technical users who need to reduce binary size while retaining runtime behavior for most supported formats. It also supports multi-architecture use and perpetual licensing.

Compression control is a central strength. Users can select levels 1 through 9 or use --best, apply brute-force and multiple-method workflows, and decompress packed files with the -d option. UPX can list compressed-file information such as size and compression ratio, test compressed and uncompressed data integrity, and maintain checksums for both forms. These features make it practical when file-size reporting and verification matter alongside packing. Its command-line design favors users comfortable working with executable files and compression options rather than teams seeking a graphical workflow.

UPX is focused on compression and packing, not verified protection features. That distinction matters when the goal extends beyond reducing distribution size. The software is distributed under GPL v2+ with special permissions for compressed commercial programs, so commercial distribution requires attention to those conditions. Choose UPX for free, cross-platform executable compression with broad format coverage and adjustable workflows. Consider another option when verified protection capabilities or a less technical operating model are central requirements.

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UPX pricing

UPX fact sheet

Alternatives to UPX

• Sentinel EnvelopeA broad executable-protection toolkit for vendors distributing software across major platforms.9.2
• SCStarForce CryptoA mature Windows packer for native and managed-code protection with configurable defenses.8.7
• PECompactA feature-rich PE packer for Windows developers who need 32-bit compression workflows.8.4

See all UPX alternatives →

UPX vs the competition

• UUPX vs Sentinel Envelope
• USCUPX vs StarForce Crypto
• UUPX vs PECompact
• UUPX vs Virbox Protector
• UUPX vs Themida
• UUPX vs Dhaedalida

Compare UPX with any tool side by side →

Featured on iTechGuides

UPX is listed in our Executable Packers directory. Add the badge to your site — it links back to this page.

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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

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Last updated 7 Oct 2026 · How we research and update