# upx/upx

UPX - the Ultimate Packer for eXecutables

Repository: https://github.com/upx/upx
Canonical: https://ross.abutalabs.com/products/upx
Homepage: https://upx.github.io
Language: C++
License: NOASSERTION
License Family: other
Last push: 2026-08-26T22:50:35+00:00

## Health v2 (maintenance only)
Score: 91/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 75, longevity 100
- inputs: {"age_days": 3654, "days_push": 7, "days_rel": 86, "gap_med": 75, "n_releases_24m": 6}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 17816, forks 1520 (observed 2026-08-28T04:11:20.449411+00:00)

## What it is
UPX is a free, open-source executable packer that compresses programs and DLLs by roughly 50-70% while keeping them fully self-contained and runnable. It supports many executable formats across Windows, macOS, and Linux and is written in portable C++.

## Use cases
- compress executables to reduce download size
- shrink binaries for software distribution
- pack a DLL to save disk space
- unpack a UPX-compressed binary
- reduce network load times for program downloads

## When to choose
- you need to reduce the size of distributed binaries without changing their behavior
- you want a reversible, well-documented packer with no runtime or memory penalty
- you need cross-platform support for Windows, macOS, and Linux executables

## When to avoid
- you need actual code protection or encryption - UPX explicitly provides none
- your target format is unsupported (e.g., ARM64 Windows is still pending)
- your antivirus pipeline flags packed binaries and you cannot whitelist them

## Facets
- artifact type: cli-tool
- maturity: stable
- function: compression, cli, developer-tools
- domain: developer-tools, cross-platform
- platform: windows, cli, cross-platform
- tags: executable-packer, binary-compression, self-extracting, c-plus-plus, command-line, linux, macos

## Member repositories
- upx/upx (main) score 91

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:11:20.449411+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T17:02:26.848100+00:00, confidence not recorded.
  - readme: https://github.com/upx/upx (fetched 2026-08-28T04:11:20.449411+00:00, sha 515efd86b875)
  - homepage: https://upx.github.io (fetched 2026-08-29T08:00:29.155668+00:00, sha 554dfb206ede)
- Data as of 2026-08-30T08:39:29.467469+00:00.