UPX 5.0.1 – Ultimate Packer for eXecutables

UPX (Ultimate Packer for eXecutables) is a free, portable, extendable, high-performance executable packer for several different executable formats.

It achieves an excellent compression ratio and offers very fast decompression. Your executables suffer no memory overhead or other drawbacks for most of the formats supported, because of in-place decompression.

UPX is copyrighted software distributed under the terms of the GNU General Public License. And with special exceptions granting the free usage for commercial programs as stated in the UPX License Agreement.

This app uses the NRV compression library for compression services. A compatible but somewhat less efficient OpenSource implementation is available through the UCL compression library.

UPX Features:

• Excellent compression ratio: typically compresses better than WinZip, Zip, Gzip. Use UPX to decrease the size of your distribution!
• Very fast decompression: ~10 MB/sec on an ancient Pentium 133, ~200 MB/sec on an Athlon XP 2000+.
• No memory overhead for your compressed executables because of in-place decompression.
• Safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.
• Universal: can pack a number of executable formats.
• Portable: UPX is written in portable endian-neutral C++.
• Extendable: because of the class layout it’s very easy to add new executable formats or new compression algorithms.
• Free: Distributed with full source code under the GNU General Public License v2+. With special exceptions granting the free usage for commercial programs as stated in the License Agreement.

Changes in version 5.0.1 (2025-05-06)::

• Bug fixes

Changes in version 5.0.0 (202-05-20):

• ELF: use of memfd_create supports Enforcing mode of SELinux
• ELF: two-step de-compression enables future per-PT_LOAD work
• ELF: –unmap-all-pages completely avoids /proc/self/exe
• ELF: PT_MIPS_ABIFLAGS is now forwarded into the compressed output; qemu-mips can choose the right floating-point emulation
• ELF: many minor internal changes fix nits revealed by fuzzing
• bug fixes

Changes in version 4.2.4 (9 May 2024):

• bug fixes

Changes in version 4.2.1 (1 Nov 2023)::

• linux: /proc/self/exe now is optional
• windows: use SetFileTime to preserve sub-second file timestamps
• official Windows builds: revert activeCodePage change introduced in 4.2.0
• bug fixes

Changes in version 4.2.0 (26 Oct 2023)::

• win32/pe and win64/pe: stricter relocation checks; please report regressions
• new option ‘–link’ to preserve hard-links (Unix only; use with care)
• add support for NO_COLOR env var; see https://no-color.org/
• disable macOS support until we fix compatibility with macOS 13+
• bug fixes

Homepage – https://upx.github.io

Size: 628 KB

DOWNLOAD for Windows 32-bit

DOWNLOAD for Windows 64-bit

DOWNLOAD for Linux i386

DOWNLOAD for Linux AMD64

DOWNLOAD for Linux ARM64

DOWNLOAD DOS version

All DOWNLOADS