#i18n #locale #internationalization


Maintains locale preferences for process and thread and initialises them by inspecting the system for user preference

7 releases

Uses old Rust 2015

0.3.0 Aug 22, 2019
0.2.3 Jul 10, 2019
0.2.2 Apr 21, 2017
0.2.1 Jan 9, 2017
0.1.1 Dec 30, 2016

#67 in Operating systems

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81,149 downloads per month
Used in 60 crates (14 directly)

MIT license


TravisCI Build Status AppVeyor Build Status Crates.io Version Docs.rs


Remembers locale configuration per-thread and per-process and initializes the values by inspecting the system for user preferences.


You can depend on this library by adding locale_config to your Cargo dependencies:

locale_config = "*"

Usually it is not recommended to depend on *, but in this case it is important that incompatible version requirements don't cause multiple versions to be pulled in the final binary, so I do recommend it here and promise I will maintain good compatibility. Just please don't add traits to the types defined here to avoid conflicts with potential future methods.


Usually you want to use this indirectly via a localization crate like locale. However if you need to work with the identifier itself, or you need to override it, use


to find what you should be using at any given point in the application,


to override it for current thread and


to override it for new threads.

In case you need to access the initial value, you'll find it under


The value may contain language tags specific for various localization aspects, called categories, and fallbacks. The Locale::tags_for method will take care of selecting relevant tags for you. For preferred language of translations, use


For formatting, use categories "numeric" for numbers, "time" for date and time and "monetary" for money amounts. And use "collate" for collation.

Note that this crate does not itself provide any translation, formatting nor collation functionality. Formatting and collation will be provided by locale crate, translation has multiple available implementations.

See full documentation on Docs.rs or github.

Supported systems

  • Unix: Using the POSIX standard environment variables LANG, LC_* and LANGUAGES. The variables are recognized on all systems and take precedence on most of them.

  • Windows: Vista and newer

    • Uses API available from Vista and Server 2008 only.
    • The GetUserPreferredUILanguages is only available for desktop, but not store applications. Store applications should have equivalent functionality, but I didn't try accessing it from Rust yet.
    • Customization to individual locale elements done in “Regional and Language options” (digits, calendar, decimal and thousand separator etc.) are not detected (yet).
    • Not well tested.
  • OS X: Reads setting from NSLocale, can be overridden by setting the Unix environment variables.

  • CGI: The HTTP_ACCEPT_LANGUAGE environment variable is used if detected. Hopefully it is specific enough to the CGI environment that it can be used whenever detected.



  • Support OS X NSLocale. Thanks Sophie Tauchert (@999eagle).


  • Try support getting locale in emscripten targets in browser. Unfortunately the emscripten targets seem to have broken in cross meanwhile, so they are not being tested.
  • Update to winapi 0.3.
  • Update ro regex 1.0.


  • Update dependencies: regex 0.2.


  • Interpret some overrides that can be set on Windows in Region and Language dialog, namely: group, decimal and list separators, first day of week, 12/24-hour time, measurement system, (decimal) number system, to an extent negative monetary value format (only whether to use parenthesized format or not) and to an extent date format (if ISO-8601 variant is selected).


  • Changed error handling to proper error type.


  • Added basic Windows support.


  • Initial version, with Unix and CGI support.


~55K SLoC