Fallbacking

fallbackLocale: '<lang>' to choose which language to use when your preferred language lacks a translation.

Implicit fallback using locales

If a locale is given containing a territory and an optional dialect, the implicit fallback is activated automatically.

For example de-DE-bavarian would fallback

1. de-DE-bavarian
2. de-DE
3. de

To suppress the automatic fallback, add the postfix exclamation mark !, for example de-DE!

Explicit fallback with one locale

Sometimes some items will not be translated into some languages. In this example, the item hello is available in English but not Japanese:

const messages = {
  en: {
    hello: 'Hello, world!'
  },
  ja: {
  }
}

If you want to use (say) en items when an item is not available in your desired locale, set the fallbackLocale option in the createI18n:

const i18n = createI18n({
  locale: 'ja',
  fallbackLocale: 'en',
  messages
})

Template:

<p>{{ $t('hello') }}</p>

Output:

<p>Hello, world!</p>

By default, falling back to fallbackLocale generates two console warnings:

[intlify] Not found 'hello' key in 'ja' locale messages.
[intlify] Fall back to translate 'hello' key with 'en' locale.

The first warning message is printed the key, due to given to the translation function $t is not in the ja locale messages and the second warning message that comes out when you fall back to resolve localized messages from en locale messages. These warning messages are output to support debugging using Vue I18n.

NOTE

These warning messages are only warned in development mode (process.env.NODE_ENV !== 'production') by default, not for production.

To suppress the first warning(Not found key...), set silentTranslationWarn: true in Legacy API mode or set missingWarn: false in Composition API mode when initializing the createI18n.

To suppress the second warning(Fall back to...), set silentFallbackWarn: true in Legacy API mode or set fallbackWarn: false in Composition API mode when initializing the createI18n.

Explicit fallback with an array of locales

It is possible to set more than one fallback locale by using an array of locales. For example

fallbackLocale: [ 'fr', 'en' ],

Explicit fallback with decision maps

If more complex decision maps for fallback locales are required, it is possible to define decision maps with according fallback locales.

Using the following decision map:

fallbackLocale: {
  /* 1 */ 'de-CH':   ['fr', 'it'],
  /* 2 */ 'zh-Hant': ['zh-Hans'],
  /* 3 */ 'es-CL':   ['es-AR'],
  /* 4 */ 'es':      ['en-GB'],
  /* 5 */ 'pt':      ['es-AR'],
  /* 6 */ 'default': ['en', 'da']
},

Will result in the following fallback chains:

locale	fallback chains
'de-CH'	de-CH > fr > it > en > da
'de'	de > en > da
'zh-Hant'	zh-Hant > zh-Hans > zh > en > da
'es-SP'	es-SP > es > en-GB > en > da
'es-SP!'	es-SP > en > da
'fr'	fr > en > da
'pt-BR'	pt-BR > pt > es-AR > es > en-GB > en > da
'es-CL'	es-CL > es-AR > es > en-GB > en > da

Fallback interpolation

Set formatFallbackMessages: true to do template interpolation on translation keys when your language lacks a translation for a key.

Since the keys to the translations are strings, you can use a user-readable message (for a particular language) as a key. E.g.

const messages = {
  ja: {
    'Hello, world!': 'こんにちは、世界!'
  }
}

This is useful because you don’t have to specify a translation for the string "Hello, world!" into English.

In fact, you can even include template parameters in a key. Together with formatFallbackMessages: true, this lets you skip writing templates for your "base" language; the keys are your templates.

const messages = {
  ru: {
    'Hello {name}': 'Здравствуйте {name}'
  }
}

const i18n = createI18n({
  locale: 'ru',
  fallbackLocale: 'en',
  formatFallbackMessages: true,
  messages
})

When the template is as below:

<p>{{ $t('Hello {name}', { name: 'John' }) }}</p>
<p>{{ $t('The weather today is {condition}!', { condition: 'sunny' }) }}</p>

The following will be output:

<p>Здравствуйте, John</p>
<p>The weather today is sunny!</p>