UPX (Ultimate Packer for eXecutables) is a free and open source executable packer supporting a number of file formats from different operating systems.
UPX uses a data compression algorithm called UCL, which is an open-source implementation of portions of the proprietary NRV (Not Really Vanished) algorithm.
UCL has been designed to be simple enough that a decompressor can be implemented in just a few hundred bytes of code. UCL requires no additional memory to be allocated for decompression, a considerable advantage that means that a UPX packed executable usually requires no additional memory.
UPX (since 2.90 beta) can use LZMA on most platforms; however, this is disabled by default for 16-bit due to slow decompression speed on older computers (use --lzma to force it on).
Starting with version 3.91, UPX also supports 64-Bit (x64) PE files on the Windows platform. This feature is currently declared as experimental.
What is UPX?
UPX by UPX (developed by Markus F.X.J. Oberhumer) is open-source Windows software in the archivers category. It ranks 4th by popularity among archivers in this catalogue. It is written in C++ and assembly language. Besides Windows, it is available for GNU/Linux, macOS, Atari TOS and DOS.
Installation and requirements
The publisher provides Portable installers for 64-bit and 32-bit Windows. It runs without installation (portable).
Updates and version history
The current version is 5.2.1, released on August 27, 2026. The version history goes back to November 16, 2022: 15 releases, all linked to the official files. That is about 4 releases a year.
Popularity and file types
The Chocolatey package has been downloaded 230,651 times. The source code on GitHub (upx/upx) has 17,959 stars. Wikipedia has an article about it in 11 of our languages. On Windows it registers 1 file type, including .exe. Similar programs include 7-Zip, PeaZip and Zstandard.
Project description on GitHub: “UPX - the Ultimate Packer for eXecutables”
Pros / Cons
Pros
- Open source: the code can be inspected and built by anyone
- Portable: runs without installation
- Updated in the last two months
- Also runs on GNU/Linux, macOS and Atari TOS
- Large user base
Cons
- No native ARM64 build
In short: UPX is an open-source archiver tool for 64-bit and 32-bit PCs.
Screenshots
Is UPX safe to download?
- The file is served by github.com, the publisher’s own domain
- The download link uses HTTPS
- A SHA256 hash is published, so you can verify the file:
EABC6792A347D45E945BE7748423E7868FD01B0D2BCAA2F4B1031FD71FF69BDA· Open the VirusTotal report for this hash - The link has not been checked yet
- The source code is public
- ExeAtlas does not host, wrap or modify installers
Related guide: How to check a file’s SHA256 hash on Windows
Security practices (OpenSSF Scorecard)
Automated checks of the upx/upx repository on GitHub by the Open Source Security Foundation, last run on October 19, 2026.
- Actively maintained10
- Fuzzing10
- Licence declared9
- No binaries in the repository7
- Security policy3
- Code review0
- No dangerous workflows0
- Restricted token permissions0
- OpenSSF Best Practices badge0
- Pinned dependencies0
- Signed releases0
- Static code analysis0
The score rates how the project is developed and released, not whether the program is safe to install. scorecard.dev
Recent versions
All 15 versions ›15 versions over 4 years · about 4 a year
| Version | Date | Size | Files |
|---|---|---|---|
| 5.2.1Latest | August 27, 2026 | — | 32-bit ZIP64-bit ZIP |
| 5.2.0 | June 8, 2026 | — | 64-bit ZIP32-bit ZIP |
| 5.1.1 | March 5, 2026 | — | 64-bit ZIP32-bit ZIP |
| 5.1.0 | January 7, 2026 | — | 32-bit ZIP64-bit ZIP |
| 5.0.2 | July 20, 2025 | — | 32-bit ZIP64-bit ZIP |
| 5.0.1 | May 6, 2025 | — | 32-bit ZIP64-bit ZIP |
| 5.0.0 | February 20, 2025 | — | 32-bit ZIP64-bit ZIP |
| 4.2.4 | May 9, 2024 | — | 32-bit ZIP64-bit ZIP |
Install from the command line
Silent install ›winget install --id UPX.UPX -echoco install upx -yscoop install main/upxRelated guide: How to use winget: install and update apps
Also for other systems
brew install upxInformation
- Publisher
- UPX
- Developer
- Markus F.X.J. Oberhumer
- Category
- Archivers
- Licence
- GPL-2.0-or-later
- Price
- Free
- Source code
- github.com/upx/upx
- Written in
- C++ and assembly language
- Requires
- Windows 11 / 10
- Architecture
- 64-bit, 32-bit
- Installer
- Portable
- Other platforms
- GNU/Linux, macOS, Atari TOS, DOS
- Version
- 5.2.1
- Released
- August 27, 2026
- Added to the catalogue
- February 10, 2023
- Versions listed
- 15
- Updates / year
- 4
- Chocolatey downloads
- 230,651
- GitHub stars
- 17,959
- GitHub forks
- 1,539
- Website
- upx.github.io
- winget ID
- UPX.UPX
- Chocolatey package
- upx
- Scoop package
- main/upx
File types it opens (1)
Ratings and reviews
No reviews yet. Be the first to rate it.
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Frequently asked questions
Is UPX free?
Yes. UPX is open-source software under the GPL-2.0-or-later licence.
Is UPX safe to download?
The download comes from github.com, which belongs to the publisher; ExeAtlas does not host or change the file. Compare its SHA256 hash with the one shown here, or open the VirusTotal report for that hash.
How do I install UPX with winget?
Open PowerShell or Windows Terminal and run the winget command shown on this page. winget downloads the official installer and checks its SHA256 hash before running it.
Does UPX run on ARM (Windows on Arm)?
There is no ARM64 build; Windows 11 on Arm can run the 64-bit and 32-bit version through emulation.
Where can I download an older version of UPX?
The versions page lists all 15 versions with links to their official installer files, back to November 16, 2022.
Can I use UPX without administrator rights?
Yes, it is portable: unpack and run it.
What are alternatives to UPX?
7-Zip, PeaZip, Zstandard, WinRAR and 7-Zip ZS. The alternatives page compares them.
