C.UTF-8 (or POSIX.UTF-8) locale support

Last-Modified: 2026-05-07

Implementations

• 2014-07-02: C.UTF-8 explicitly added in musl with commit 0bc03091bb674ebb9fa6fe69e4aec1da3ac484f2 adding a locale framework (which already used UTF-8 by default)
• 2016-01-05: Python PEP 540 – Add a new UTF-8 Mode
• 2016-12-28 ~ 2017-05-09: Python PEP 0538 – Coercing the legacy C locale to a UTF-8 based locale
• 2018-03: OpenBSD 6.3+ setlocale() adds support for .UTF-8, no other .charset is supported
• 2022-02-03: C.UTF-8 added in glibc 2.35
• 2022-02-15: C.UTF-8 added in Solaris 11.4.42
• 2024-03-19: PostgreSQL 17 adds a builtin C.UTF-8 locale with commit f69319f2f1fb16eda4b535bcccec90dff3a6795e

Standardization

• 2013-03-28 ~ 2015-07-02: POSIX discussion in Austin Group Bug #663, bugnote 1669: We should add an optional POSIX.UTF-8 locale in Issue 8, […] and in the interpretation response: We are also seeking proposals for the standardization of a "POSIX.UTF-8" locale for Issue 8.
• 2022-01-11 - present: POSIX proposal Austin Group Bug #1548: Addition of a POSIX.utf-8 locale (likely as 7.3 "POSIX.utf-8 locale")
• 2025-05-04: ISO/SC22/WG14/C-Language N3539 Jabot, Preserving LC_CTYPE at program start for UTF-8 locales