API

init

i18next.init(options, callback) // -> returns a Promise

The default export of the i18next module is an i18next instance ready to be initialized by calling init. You can create additional instances using the createInstance function.

Please read the options page for details on configuration options.

The callback will be called after all translations were loaded or with an error when failed (in case of using a backend).

So you should wait for init to complete (wait for the callback or promise resolution) before using the t function!

In case of react-i18next make sure useSuspense is enabled or handle the ready state in HOCs or hooks yourself.

Do not call init multiple times. To change language use changeLanguage. If you need complete different configs use createInstance or cloneInstance.

An error can occur if for example there was a loading issue when using a backend plugin.

JavaScript

i18next.init({
  fallbackLng: 'en',
  ns: ['file1', 'file2'],
  defaultNS: 'file1',
  debug: true
}, (err, t) => {
  if (err) return console.log('something went wrong loading', err);
  t('key'); // -> same as i18next.t
});

// with only callback
i18next.init((err, t) => {
  if (err) return console.log('something went wrong loading', err);
  t('key'); // -> same as i18next.t
});

// using Promises
i18next
  .init({ /* options */ })
  .then(function(t) { t('key'); });

TypeScript

use

i18next.use(module)

The use function is there to load additional plugins to i18next.

For available module see the plugins page and don't forget to read the documentation of the plugin.

import i18next from 'i18next';
import Backend from 'i18next-http-backend';
import Cache from 'i18next-localstorage-cache';
import postProcessor from 'i18next-sprintf-postprocessor';
import LanguageDetector from 'i18next-browser-languagedetector';

i18next
  .use(Backend)
  .use(Cache)
  .use(LanguageDetector)
  .use(postProcessor)
  .init(options, callback);

t

i18next.t(keys, options)

Please have a look at the translation functions like interpolation, formatting and plurals for more details on using it.

JavaScript

You can specify either one key as a String or multiple keys as an Array of String. The first one that resolves will be returned.

i18next.t('my.key'); // -> will return value in set language

i18next.t(['unknown.key', 'my.key']); // -> will return value for 'my.key' in set language

TypeScript

exists

i18next.exists(key, options)

Uses the same resolve functionality as the t function and returns true if a key exists.

i18next.exists('my.key'); // -> true if exists, false if not

getFixedT

i18next.getFixedT(lng, ns, keyPrefix)

Returns a t function that defaults to given language or namespace.

All arguments can be optional/null.

lng and ns params could be arrays of languages or namespaces and will be treated as fallbacks in that case.

The optional keyPrefix will be automatically applied to the returned t function. i.e.

JavaScript

const t = i18next.getFixedT(null, null, 'user.accountSettings.changePassword')
const title = t('title'); // same as i18next.t('user.accountSettings.changePassword.title');

TypeScript

If you want to use keys with a prefixed namespace and the keyPrefix argument was provided, you'll need to override it in the t function options.

See below for an example.

JavaScript

const t = i18next.getFixedT(null, null, 'user.accountSettings.changePassword')
const title = t('ns:title'); // this will not work
const title = t('ns:title', { keyPrefix: '' }); // this will work

TypeScript

On the returned function you can like in the t function override the languages or namespaces by passing them in options or by prepending namespace.

JavaScript

// fix language to german
const de = i18next.getFixedT('de');
de('myKey');

// or fix the namespace to anotherNamespace
const anotherNamespace = i18next.getFixedT(null, 'anotherNamespace');
anotherNamespace('anotherNamespaceKey'); // no need to prefix ns i18n.t('anotherNamespace:anotherNamespaceKey');

TypeScript

changeLanguage

i18next.changeLanguage(lng, callback) // -> returns a Promise

Changes the language. The callback will be called as soon translations were loaded or an error occurs while loading.

Calling changeLanguage without lng uses the language detector to choose the language to set.

HINT: For easy testing—setting lng to 'cimode' will cause the t function to always return the key.

JavaScript

i18next.changeLanguage('en', (err, t) => {
  if (err) return console.log('something went wrong loading', err);
  t('key'); // -> same as i18next.t
});

// using Promises
i18next
  .changeLanguage('en')
  .then((t) => {
    t('key'); // -> same as i18next.t
  });

// manually re-detecting language
i18next.changeLanguage().then(...)

TypeScript

language

i18next.language

Is set to the current detected or set language.

If you need the primary used language depending on your configuration (supportedLngs, load) you will prefer using i18next.resolvedLanguage or i18next.languages[0].

languages

i18next.languages

Is set to an array of language codes that will be used to look up the translation value.

When the language is set, this array is populated with the new language codes. Unless overridden, this array is populated with less-specific versions of that code for fallback purposes, followed by the list of fallback languages.

Values are unique, so if they appear earlier in the array, they will not be added again.

// initialize with fallback languages
i18next.init({
  fallbackLng: ["es", "fr", "en-US", "dev"]
});

// change the language
i18next.changeLanguage("en-US-xx");

// new language and its more generic forms, followed by fallbacks
i18next.languages; // ["en-US-xx", "en-US", "en", "es", "fr", "dev"]

// change the language again
i18next.changeLanguage("de-DE");

// previous language is not retained
i18next.languages; // ["de-DE", "de", "es", "fr", "en-US", "dev"]

resolvedLanguage

i18next.resolvedLanguage

Is set to the current resolved language. It can be used as primary used language, for example in a language switcher.

(introduced in v21.0.0)

hasLoadedNamespace

i18next.hasLoadedNamespace(ns, options) // -> returns true or false

Checks if namespace has loaded yet. i.e. used by react-i18next

loadNamespaces

i18next.loadNamespaces(ns, callback) // -> returns a Promise

Loads additional namespaces not defined in init options.

i18next.loadNamespaces('myNamespace', (err) => { /* resources have been loaded */ });
i18next.loadNamespaces(['myNamespace1', 'myNamespace2'], (err) => { /* resources have been loaded */ });

// using Promises
i18next
  .loadNamespaces(['myNamespace1', 'myNamespace2'])
  .then(() => {});

loadLanguages

i18next.loadLanguages(lngs, callback) // -> returns a Promise

Loads additional languages not defined in init options (preload).

i18next.loadLanguages('de', (err) => { /* resources have been loaded */ });
i18next.loadLanguages(['de', 'fr'], (err) => { /* resources have been loaded */ });

// using Promises
i18next
  .loadLanguages(['de', 'fr'])
  .then(() => {});

reloadResources

i18next.reloadResources() // -> returns a Promise

Reloads resources on given state. Optionally you can pass an array of languages and namespaces as params if you don't want to reload all.

// reload all
i18next.reloadResources();

// reload languages
i18next.reloadResources(['de', 'fr']);

// reload namespaces for all languages
i18next.reloadResources(null, ['ns1', 'ns2']);

// reload namespaces in languages
i18next.reloadResources(['de', 'fr'], ['ns1', 'ns2']);

// reload a namespace in a language
i18next.reloadResources('de', 'ns1');

// optional third param callback i18next@>=11.9.0
i18next.reloadResources('de', 'ns1', () => { /* reloaded */ });

// using Promises
i18next
  .reloadResources()
  .then(() => {});

setDefaultNamespace

i18next.setDefaultNamespace(ns)

Changes the default namespace.

dir

i18next.dir(lng)

Returns rtl or ltr depending on languages read direction.

// for current language
i18next.dir();

// for another language
i18next.dir('en-US'); // -> "ltr";
i18next.dir('ar'); // -> "rtl";

format

i18next.format(data, format, lng)

introduced in v8.4.0 and legacy since v21.3.0

Exposes interpolation.formatt function added on init.

For formatting used in translation files checkout the formatting doc.

JavaScript

// key = 'hello {{what}}'
i18next.t('key', { what: i18next.format('world', 'uppercase') }); // -> hello WORLD

TypeScript

instance creation

createInstance

i18next.createInstance(options, callback)

Will return a new i18next instance.

Please read the options page for details on configuration options.

Providing a callback will automatically call init.

The callback will be called after all translations were loaded or with an error when failed (in case of using a backend).

JavaScript

const newInstance = i18next.createInstance({
  fallbackLng: 'en',
  ns: ['file1', 'file2'],
  defaultNS: 'file1',
  debug: true
}, (err, t) => {
  if (err) return console.log('something went wrong loading', err);
  t('key'); // -> same as i18next.t
});

// is the same as
const newInstance = i18next.createInstance();
newInstance.init({
  fallbackLng: 'en',
  ns: ['file1', 'file2'],
  defaultNS: 'file1',
  debug: true
}, (err, t) => {
  if (err) return console.log('something went wrong loading', err);
  t('key'); // -> same as i18next.t
});

TypeScript

cloneInstance

i18next.cloneInstance(options)

Creates a clone of the current instance. Shares store, plugins and initial configuration. Can be used to create an instance sharing storage but being independent on set language or default namespaces.

const newInstance = i18next.cloneInstance({
  fallbackLng: 'en',
  defaultNS: 'file1'
});

forkResourceStore

By setting the forkResourceStore option to true, it will not shares the store.

const newInstance = i18next.cloneInstance({
  forkResourceStore: true,
  keySeparator: '[[my-new-separator]]'
});

events

Every event can be unsubscribed using

i18next.off('name', myFunction);

All attached listeners can be unsubscribed using

i18next.off('name');

onInitialized

i18next.on('initialized', function(options) {})

Gets fired after initialization.

onLanguageChanged

i18next.on('languageChanged', function(lng) {})

Gets fired when changeLanguage got called.

onLoaded

i18next.on('loaded', function(loaded) {})

Gets fired on loaded resources.

onFailedLoading

i18next.on('failedLoading', function(lng, ns, msg) {})

Gets fired if loading resources failed (after the in-built retry algorithm).

onMissingKey

i18next.on('missingKey', function(lngs, namespace, key, res) {})

Gets fired on accessing a key not existing. Needs saveMissing set to true.

store events

Please be aware the i18next.store is only available on i18next after the init call.

onAdded

i18next.store.on('added', function(lng, ns) {})

Gets fired when resources got added.

onRemoved

i18next.store.on('removed', function(lng, ns) {})

Gets fired when resources got removed.

resource handling

Can be accessed on i18next or i18next.services.resourceStore.

getResource

i18next.getResource(lng, ns, key, options)

Gets one value by given key.

options:

option	default	description
keySeparator	"."	char to separate keys, or false if no separator is preferred
ignoreJSONStructure	true	if a key is not found as nested key, it will try to lookup as flat key

addResource

i18next.addResource(lng, ns, key, value, options)

Adds one key/value.

options:

option	default	description
keySeparator	"."	char to separate keys, or false if no separator is preferred
silent	false	if set to true adding will not emit an added event

addResources

i18next.addResources(lng, ns, resources)

Adds multiple key/values.

addResourceBundle

i18next.addResourceBundle(lng, ns, resources, deep, overwrite)

Adds a complete bundle.

Setting deep (default false) param to true will extend existing translations in that file. Setting deep and overwrite (default false) to true it will overwrite existing translations in that file.

So omitting deep and overwrite will overwrite all existing translations with the one provided in resources. Using deep you can choose to keep existing nested translation and to overwrite those with the new ones.

i18next.addResourceBundle('en', 'translations', {
  key: 'value',
}, true, true);

hasResourceBundle

i18next.hasResourceBundle(lng, ns)

Checks if a resource bundle exists.

getDataByLanguage

i18next.getDataByLanguage(lng)

Returns a resource data by language.

getResourceBundle

i18next.getResourceBundle(lng, ns)

Returns a resource bundle.

removeResourceBundle

i18next.removeResourceBundle(lng, ns)

Removes an existing bundle.