:::tip You can request a new language here. :::
Weblate is a "libre software web-based continuous localization system". Immich localization efforts are managed on their hosted platform.
Plurals, numbers, dates and other locale specific message formats can be handled by using the ICU message format. Internally, this is handled by the intl-messageformat library. Their documentation includes common, editable examples via a "live editor" feature, which can be useful to test and debug message formats.
Immich currently supports the following languages: