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mimalloc (pronounced "me-malloc") is a general purpose allocator with excellent performance characteristics. Initially developed by Daan Leijen for the runtime systems of the Koka and Lean languages.

Latest release : v3.5.3 (2026-09-16) recommended.
Latest v2 release: v2.5.2 (2026-09-12) stable, legacy.
Latest v1 release: v1.15.2 (2026-09-12) legacy.

mimalloc is a drop-in replacement for malloc and can be used in other programs without code changes, for example, on dynamically linked ELF-based systems (Linux, BSD, etc.) you can use it as:

> LD_PRELOAD=/usr/lib/libmimalloc.so  myprogram

It also includes a way to dynamically override the default allocator in Windows. Notable aspects of the design include:

• small and consistent: the library is about 1