Cosmopolitan is a cross-platform C runtime library and build framework that enables the creation of single-file, self-contained executables. By providing a unified set of system headers and a specialized compiler toolchain, it allows developers to write low-level systems code that executes natively across multiple operating systems without requiring recompilation for each target environment.
The project utilizes a polyglot binary format and a system call shimming layer to intercept and translate kernel requests, effectively bypassing standard library dependencies. This approach consolidates all necessary runtime code and library dependencies directly into the executable, resulting in binaries that function immediately on target machines without external configuration or pre-installed runtimes.
This framework supports the distribution of portable software that maintains compatibility across diverse environments, including legacy systems. The project is distributed as a development toolkit, providing the necessary infrastructure to build and deploy zero-dependency applications from a single source build.