Cosmopolitan libc
Hacker ApprovedShares rank 2 of 9 c++ libraries by recommenders
Builds single binaries that run across Linux, Windows and Mac on amd64 and arm64, with a portable C library. Caveat: critics note limited adoption and lowest-common-denominator platform support issues.
Builds single binaries that run across Linux, Windows and Mac on amd64 and arm64, with a portable C library. Caveat: critics note limited adoption and lowest-common-denominator platform support issues.
35 people gave an opinion
- recommend it
- 29
- criticize it
- 6
- approval share
- 83%
Recommended in 10 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: not recommended
- May 2026: recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: recommended
- September 2026: recommended
- October 2026: recommended
- November 2026: not recommended (month in progress)
Why it carries the badge
- 29 people recommend itNeeds 10 or more, met.
- 4.8 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 10 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Runs across operating systems
“being able to write quick little utilities and then pass them around without worrying about what operating system”
Comment from 15 Jun 2026 in “Show HN: Kage – Shadow any website to a single binary for offline viewing” “It combines a polyglot format and a polymorphic libc that works in all major OSes under both amd64 and arm64.”
Comment from 21 Jan 2026 in “What Is a PC Compatible?” “you can compile a single native binary that targets Linux, Windows & Mac OS”
Comment from 26 Jan 2026 in “The Holy Grail of Linux Binary Compatibility: Musl and Dlopen” - Comment from 26 Jan 2026 in “The Holy Grail of Linux Binary Compatibility: Musl and Dlopen”
- Comment from 15 Jun 2026 in “Boot Naked Linux”
- Comment from 27 Oct 2026 in “At 14 Justine Tunney published software. Now she makes AI models run from a file”
Impressive, admired engineering
“Very few people in recent decades have achieved anything comparable to αcτµαlly pδrταblε εxεcµταblε and Cosmopolitan libc”
Comment from 31 May 2026 in “Restartable Sequences” “I love that someone is attempting this just because of the tenacity it shows.”
Comment from 30 Dec 2025 in “Win32 is the stable Linux ABI” “jart's cosmopolitan is awesome.”
Comment from 24 Jul 2026 in “Interview with Matheus Moreira about Lone Lisp and Linux Kernel” - Comment from 20 May 2026 in “Freelang – a Libc-free, direct sys/kernel call language with weird concurrency”
- Comment from 6 Jun 2026 in “Zeroserve: A zero-config web server you can script with eBPF”
- Comment from 6 Jun 2026 in “Zeroserve: A zero-config web server you can script with eBPF”
Works with OpenGL and GUI packages
“Cosmopolitan Libc has since integrated the bits to make OpenGL work in cross-platform binaries and it's awesome.”
Comment from 17 Jun 2026 in “MicroUI – A tiny, portable, immediate-mode UI library written in ANSI C” “Cosmopolitan can be used to bundle up any gui package, and your code”
Comment from 4 Mar 2026 in “Claude is an Electron App because we've lost native” Platform-agnostic static C standard library
“the core benefit proposition of Cosmopolitan is indeed a platform-agnostic, statically-linked C standard”
Comment from 26 Jan 2026 in “The Holy Grail of Linux Binary Compatibility: Musl and Dlopen” “it's the secret sauce that powers everything else”
Comment from 10 Jan 2026 in “Google Co-Founder Sergey Brin's Unretirement Is a Lesson for the Rest of Us”
What people warn about
Each mark is one comment
Unclear value and limited adoption
“Cosmopolitan is great tech, the llamafile command (the "UX for a model" part) is great, but I'm not convinced by the value of Cosmopolitan applied here.”
Comment from 1 Nov 2025 on Hacker News “And it's not like APE and Cosmo libc are seeing massive adoption”
Comment from 1 Jun 2026 in “Restartable Sequences” Platform hacks and support limits
“I'd rather have platform specific minimal binaries than a single binary with hacks.”
Comment from 15 Jun 2026 in “Show HN: Kage – Shadow any website to a single binary for offline viewing” “has many lowest common denominator platform support issues”
Comment from 26 Jan 2026 in “The Holy Grail of Linux Binary Compatibility: Musl and Dlopen”
Other c++ libraries people recommend
The four most recommended other c++ libraries, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| musl libc | 34 | 25 | 58% | 10 | — | — |
| Cosmopolitan libcThis page | 29 | 6 | 83% | 10 | — | Approved |
| glibc | 29 | 75 | 28% | 10 | — | — |
| Sp.h standard library for C | 11 | 27 | 29% | 1 | — | — |
| GLib | 6 | 3 | 67% | 4 | — | — |
What people said
34 of the 36 comments that mention it, newest first. Each links to the original comment.
“used every once in a while as a no-brainer distributable executable format”
“The Cosmo binary was overkill here.”
“It may be time to revisit cosmopolitan”
“Another way to achieve something like this is Cosmopolitan C Compiler”
“shows what's possible, though.”
“For command-line programs, you might try something like Cosmopoliton[2] instead.”
“jart's cosmopolitan is awesome.”
“would be a pretty go-like experience, I'd think”
“Cosmopolitan Libc has since integrated the bits to make OpenGL work in cross-platform binaries and it's awesome.”
“to make a binary that runs in many places including bare metal”
“being able to write quick little utilities and then pass them around without worrying about what operating system”
“I'd rather have platform specific minimal binaries than a single binary with hacks.”
“make sure to check out the portable C library used to create it, which is also fascinating”
“the portable C library used to create it, which is also fascinating”
“but this is at another level because it's all production-ready”
“And it's not like APE and Cosmo libc are seeing massive adoption”
“Very few people in recent decades have achieved anything comparable to αcτµαlly pδrταblε εxεcµταblε and Cosmopolitan libc”
“Cosmopolitan libc is legendary”
“It looks like this may be a way to actually accomplish that”
“Cosmopolitan can be used to bundle up any gui package, and your code”
“has many lowest common denominator platform support issues”
“the core benefit proposition of Cosmopolitan is indeed a platform-agnostic, statically-linked C standard”
“allows a compile once execute anywhere style type of C++ binary”
“Clearly a joke if it uses the .lol tld.”
“if you disable Windows Defender”
“you can compile a single native binary that targets Linux, Windows & Mac OS”
“And produces binaries that are smaller than a typical single-OS build.”
“It combines a polyglot format and a polymorphic libc that works in all major OSes under both amd64 and arm64.”
“it's the secret sauce that powers everything else”
“I love that someone is attempting this just because of the tenacity it shows.”
“the best I found was https://github.com/jart/cosmopolitan/releases/tag/3.1”
“For a single binary that will actually run across both architectures, see”
“Cosmopolitan libc implements pledge on Linux on top of seccomp-bpf”
“Cosmopolitan is great tech, the llamafile command (the "UX for a model" part) is great, but I'm not convinced by the value of Cosmopolitan applied here.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.