Fallback site
The Multisite module provides a fallback site. The fallback site is a special site definition that is used when no site matches the request. Think of it as a default.
| Creating a fallback.yamlfile in a light module’ssitesfolder overrides the default fallback definition.
A fallback definition is created automatically byinfo.magnolia.multisite.sites.MultiSiteManager#createDefaultFallbackSiteif no fallback exists (file-based or in the JCR). | 
| In Magnolia 6.2, a fallback site could be a folder. In Magnolia 6.3, it has to be a node. | 
Choosing a fallback site definition
When using multisite, it is common to have one main site and some additional sites.
It generally makes sense to adapt the fallback site so that it extends your main site.
Use the inherit property to reference a complete site definition.
For example, the Magnolia Travel Demo has two sites: travel-demo and sportstation. When the demo modules are installed, you can change the fallback definition to extend travel-demo site.
| The fallback definition filename must be named fallback.yaml. | 
templates:
  class: info.magnolia.module.site.templates.ReferencingPrototypeTemplateSettings
  prototypeId: your-module:pages/default-prototype-of-all-page-templates
theme:
  name: default-theme
i18n:
  class: info.magnolia.cms.i18n.DefaultI18nContentSupport
  enabled: true
  fallbackLocale: en
  locales:
    en:
      country: ''
      enabled: true
      language: en-US (1)
    fr:
      country: ''
      enabled: true
      language: fr (2)| 1 | A region-based locale en-US. | 
| 2 | A language-based locale fr.
It’s possible to use language-only or region-based locales. | 
The overrides in the example site definition below only make sense if you’ve installed the travel-demo.
!inherit:travel (1)
mappings: !override (2)
domains: !override (2)
i18n: !override (2)
  class: info.magnolia.cms.i18n.IetfI18nContentSupport (3)
  enabled: true
  fallbackLocale: fr
  locales: (4)
    fr:
      country: ''
      enabled: true
      languageTag: fr-FR (5)
    cs:
      country: ''
      enabled: true
      languageTag: cs-CZ (5)| 1 | This fallback definition includes another site definition, travel, which contains the properties mappings, domains, and i18n. | 
| 2 | The mappings,domains, andi18nproperties are overridden. | 
| 3 | The language property’s class follows the IETF BCP 47 standard. | 
| 4 | A new localesproperty is defined. | 
| 5 | IETF BCP 47 language tags. |