lib64

Lib64 is a conventional directory on many Unix-like operating systems that stores 64-bit shared libraries. It is used to separate 64-bit libraries from 32-bit libraries, helping the dynamic linker locate the correct objects at runtime and supporting systems that run programs with different ABIs (application binary interfaces).

On Linux, lib64 commonly exists as /lib64 and /usr/lib64. These directories contain 64-bit versions of standard libraries and other shared objects, for architectures such as x86_64 and aarch64. Some distributions place 64-bit libraries directly within the main /lib and /usr/lib directories or organize them under architecture-specific paths as part of multi-arch layouts. The exact arrangement can vary by distribution and architecture.

The runtime linker or dynamic loader uses these directories to load shared libraries needed by executables. Tools like ldconfig maintain a cache of discovered libraries, and configuration files such as /etc/ld.so.conf determine which library directories are scanned, including lib64 when present. The separation of 64-bit libraries from 32-bit ones helps prevent ABI conflicts and simplifies multi-ABI support on systems with both 32- and 64-bit binaries.

Not all operating systems or distributions rely on a lib64 directory; some adopt different architectural naming schemes or consolidated library trees. Nevertheless, on many 64-bit Linux systems, lib64 remains a core part of the filesystem hierarchy for organizing 64-bit shared libraries.