--- title: Determine languages slug: cms-12/docs/determining-languages docTags: createdAt: 2026-08-10T15:55:59.000Z --- When describing the language concept in Optimizely Content Management System (CMS), the following language setting types are mentioned: - **System language** – Used to control date/time formatting, sort order, and so on. - **User interface language** – Controls the localized (translated) resources to display, and determines the language of the user interface. - **Content language** – The preferred language when displaying content. See [Globalization](docId\:YC4RpRcW931yDW4hUb1Ym) for information about the language management concept in CMS. ## Determine system language You can determine the current value by reading `CultureInfo.CurrentCulture` and set by setting `Thread.CurrentThread.CurrentCulture`. The information is a `CultureInfo` object and you can retrieve the language code (en-GB, sv-SE, and so on) from `CultureInfo.Name`. :::hint{type="info"} **Note** `CurrentCulture` cannot be a neutral culture because its primary purpose is to provide sorting and formatting information. This means that the language code must be something like en-GB or sv-SE. Trying to use a neutral culture results in an exception when assigning the culture to `CurrentCulture`. ::: The following rules determine the system language: - If not in edit or admin user interface, use the content language. - If a user is logged in and sets a preferred language, use the personalized language selection for this user. - Use the setting from `GlobalizationSettingsOptions.CultureLanguageCode`. If culture is set to Auto, the language preferences from the web browser are used. ## Determine user interface language You can determine the current value by reading `CultureInfo.CurrentUICulture` and set `Thread.CurrentThread.CurrentUICulture`. The information is a `CultureInfo` object, and you can retrieve the language code (en, sv, and so on) from `CultureInfo.Name`. `CurrentUICulture` can be a neutral culture (which means `CultureInfo.GetCulture("en")` would return a valid culture for `CurrentUICulture`) because `CurrentUICulture` is never used for sorting or formatting. The following rules determine the user interface language: - If not in edit or admin user interface, use the content language. - If a user is logged in and sets a preferred language, use the personalized language selection for this user. - Use the setting from `GlobalizationSettingsOptions.UICultureLanguageCode`. If culture is set to Auto, the language preferences from the web browser are used. ## Determine content language You can determine the current value by reading `IContentLanguageAccessor.Language` or through static accessor `ContentLanguage.PreferredCulture`. You can change the value by assigning this property. Content language can be a neutral culture. If a specific culture is required (for example, for sorting or formatting), then method `CultureInfo.CreateSpecificCulture` can be used on-demand and follows the .NET rules for determining a specific culture from a neutral culture. See [CultureInfo.CreateSpecificCulture](https://docs.microsoft.com/en-us/dotnet/api/system.globalization.cultureinfo.createspecificculture?view=net-5.0). The preferred content language is determined by the following rules: - That language is used if you have defined the hostname to be associated with a specific language. The setting is specified under **Manage Sites** in the admin view. - If there is a language segment in the URL (like `http://company.com/en/info`), that language is used (en). - If you are in the edit view and have selected a specific language site from the **Sites** section, that language is used. - If the requests contain a query parameter or cookie named **epslanguage**, use the language defined by the query or cookie. - If the setting `GlobalizationSettingsOptions.UseBrowserLanguagePreferences` is true, then the language preference from the web browser is used. - Use the language mapped to wildcard host '\*' if specified. - Fetch the setting from the `GlobalizationSettingsOptions.UICultureLanguageCode`. - If nothing else is discovered, use the first enabled language branch defined in Admin / Language Branches, meaning it can be viewed as the default language. :::hint{type="info"} **Note** After you determine the preferred content language, there is another step that uses the preferred content language to determine the actual language to display. If the current content does not exist for the preferred content language, a language fallback process is started. For pages, this is defined by the page language settings in the edit view. See [Globalization scenarios](docId:_TKMvNKHsYDtbek1PKHKV) for information about language-specific content settings in CMS. ::: ## Strict language routing Strict language routing causes the display of an error message if the URL and language-host mapping do not match. The following examples show how the language routing works. Say, for example, that on a website, there is a page under **root** named **News** in English and **Nyheter** in Swedish. Given that no language mapping is defined for site hosts in the configuration file, the URLs are handled as follows: - `http://localhost/News/` (404 because when not having language-host mapping in config language segment must be present) - `http://localhost/en/News/` (page in English) - `http://localhost/sv/Nyheter/` (page in Swedish) - `http://localhost/Nyheter/` (404 as in point 1) - `http://localhost/en/Nyheter/` (404 because the language for a page with the URL segment does not match the language segment) When a language-to-host mapping is defined, then a URL like `http://localhost/en/News/` produces a 404, because when there is a host mapping that defines a language, the language should not be present in the URL. You can modify the strict language routing behavior by setting `RoutingOptions.StrictLanguageRouting`, that you can set to false to get a more "tolerant" behavior.