UPX
UPX compresses executable files and is presented as a free, secure, portable packer on its project homepage.
About UPX
UPX compresses executable files, including Windows programs and DLLs, macOS apps and Linux executables. Compressed programs and libraries are self-contained and run as before, with no runtime or memory penalty for most supported formats. File size reduction for programs and DLLs is typically around 50%-70%.
It can list, test and unpack executables and maintains checksums of compressed and uncompressed files. Full source code is available under the GNU General Public License v2+, with an option for use with commercial programs under the UPX License Agreement.
Key features
- Compresses Windows programs and DLLs, macOS apps, Linux executables
- Produces self-contained executables that run without separate runtime
- Lists, tests and unpacks compressed executables
- Maintains checksums of compressed and uncompressed files
- In-place decompression avoids memory overhead for compressed files
- Decompresses at over 500 MB/sec on reasonably modern machines
Best for: People who distribute Windows, macOS, or Linux software and need smaller executable files.
Good for
- Typically reduces program and DLL file size by around 50%-70%
- Compressed files are self-contained and run as before
- Allows listing, testing and unpacking with internal checksums
Watch out for
- No runtime or memory penalty applies to most, not all, supported formats
UPX at a glance
- Website
- upx.github.io
- Category
- Software & Utilities › File Utilities
- Type
- Website
- Pricing
- Not confirmed. Check the site
- Platforms
- Linux, macOS, Web, Windows
- Open source
- Not stated
- Language
- English
- Last checked
- Oct 5, 2026 · Online when checked
- Listed
- Oct 5, 2026
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UPX FAQ
What file types does UPX compress?
Windows programs and DLLs, macOS apps and Linux executables.
Do compressed programs need extra software to run?
No, compressed programs and libraries are self-contained and run as before.
Can UPX be used with commercial applications?
Yes, it may be distributed and used freely, even with commercial applications, under its license terms.
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