Migration Guide

v22.x.x to v23.0.0

Redesigned TypeScript types

This PR redesigned the types to be less complex, faster and easier to maintain. The redesign endeavors to enhance the approach to parsing and inferring keys for the t function. Instead of performing a recursive examination of each key-value pair in resources associated with specific namespace(s) each time the t function is invoked, we generate a comprehensive set of keys from all namespaces just once.

Make sure your tsconfig compilerOptions has the strict flag or the strictNullChecks set to true.

Also use TypeScript v5.

More information: Features and Breaking changes


  • When loading multiple namespaces (react-i18next), t function will infer and accept the keys for the first namespace. So this pattern will be accepted now:

  • t function will now infer and accept the keys for the main namespace (i18next):

  • We're introducing a new type (returnObjects) that will infer fewer keys if set to false, and all keys and sub-keys if set to true. If the option returnObjects from t function is set to true, it'll work the same way:

Screenshot 2023-02-12 at 9 52 07 PM

Screenshot 2023-02-12 at 9 57 43 PM

  • t function will now infer interpolation values, but it'll only work if the translation files (resources) are placed in a ts file and using as const (like this) or an interface in a d.ts file (can be generated like this), JSON files don't support as const to convert objects to be type literals (yet).

Breaking changes

All breaking changes described below are minor ones:

  1. Projects with the option returnObjects set as true by default will also have to set the same option in the CustomTypeOptions type. Otherwise, only complete keys will be allowed (key1.key2.key3...).

 // i18next.d.ts
 import 'i18next';
 declare module 'i18next' {
    interface CustomTypeOptions {
     returnObjects: true
  1. Renaming StringMap to $Dictionary, and we'll no longer export it. $Dictionary is an internal helper, and there is no reason to expose it. If needed, you can create a copy and reuse it in your project.

  2. ns property from InterpolationOptions type will be constrained to Namespace rather than string or readonly string[].

  3. Renaming KeysWithSeparator type to JoinKeys, and it will no longer be exposed.

  4. Renaming TFuncKey type to ParseKeys.

  5. Removing NormalizeByTypeOptions type.

  6. Renaming DefaultTFuncReturnWithObject type to DefaultTReturn. It will accept TOptions as generic constraint and will no longer be exposed.

  7. Removing DefaultTFuncReturn type in favor of DefaultTReturn.

  8. Removing NormalizeReturn type.

Removed setDebug function in internal logger

Based on this discussion we decided to remove the setDebug function.

Changed default value for returnNull option to false

To improve the usage for TypeScript users (in combination with React.js) we decided to set the returnNull value to false by default. More information can be found here.

Dropped support for old browsers and Node.js < v12

To have smaller builds and faster loads, we now transpile only for modern browsers and runtimes. More information can be found here.

Prefixed ordinal plural keys

To help translators, ordinal plural keys are now prefixed with _ordinal.

v21.x.x to v22.0.0

Since this is a major rewrite for TypeScript usage we decided to create a major version. For JavaScript users v22.0.0 is equivalent to 21.10.0

v20.x.x to v21.0.0

One of the biggest breaking changes is regarding suffixing plurals. This change streamlines the suffix with the one used in the Intl API. You may need to polyfill the Intl.PluralRules API, in case it is not available it will fallback to the i18next JSON format v3 plural handling. To enforce old behaviour you can enable compatibilityJSON = 'v3' on i18next init call.

import i18next from 'i18next';

  compatibilityJSON: 'v3'
}, (err, t) => { /* resources are loaded */ });

There is also support for ordinal numbers (referring to the ordering or ranking of things, e.g. "1st", "2nd", "3rd" in English). Learn more about plurals: https://www.i18next.com/translation-function/plurals

To convert your existing translations to the new v4 format, have a look at i18next-v4-format-converter or this web tool. (It will only handle keys with the default pluralSeparator _)

skipOnVariables = true

By default the skipOnVariables option now is set to true. To enforce old behaviour you can set skipOnVariables = false on i18next init call.

import i18next from 'i18next';

  interpolation: {
    skipOnVariables: false
}, (err, t) => { /* resources are loaded */ });

natural language detection

i18next now automatically tries to detect natural language keys. This way there is no need to set nsSeparator or keySeparator option to false. In case you want to skip this natural language detection, provide a keySeparator and/or a nsSeparator option.

removed deprecated

The old deprecated whitelist options and functions have been definitively removed.

  • rename option whitelist to supportedLngs

  • rename option nonExplicitWhitelist to nonExplicitSupportedLngs

  • rename function languageUtils.isWhitelisted to languageUtils.isSupportedCode

new resolvedLanguage

There is a new i18next.resolvedLanguage property, that represents the current resolved language. It can be used as primary used language, for example in a language switcher.


If passing the ns option, the defaultNS will, by default, be set to the first ns passed.

v19.x.x to v20.0.0

There should not be any breaking change, but regarding of some misuse of i18next that pop up in last minor releases, we opted for a major version this time. The relevant change behind the scene for this major version was ignoreJSONStructure.

v18.x.x to v19.0.0

Typescript use export default for esm-first approach 1352. No API changes.

v17.x.x to v18.0.0

  • When calling i18next.changeLanguage() both i18next.language and i18next.languages will be set to the new language after calling loadResources -> means when accessing t function meanwhile you will get still the translations for the previous language instead of the fallback.

  • When is this breaking? this does not break any current test - but if you depend on accessing i18next.language or i18next.dir during language change and expect the new language this will break your app.

  • Reasoning: In react-i18next we get in a not ready state for loaded translations while we would prefer just waiting for the new language ready and trigger a rerender then - also a triggered rerender outside of the bound events would end in Suspense...

  • How can I get the language i18next will be set to? i18next.isLanguageChangingTo is set to the language called

v16.x.x to v17.0.0

  • removes named exports in index.js to avoid issues in bundlers

v15.x.x to v16.0.0

  • Build process was updated - no API changes

  • note: dist/es -> dist/esm, dist/commonjs -> dist/cjs (individual files -> one bundled file)

v14.x.x to v15.0.0

  • Build process was updated - no API changes

v13.x.x to v14.0.0

  • Breaking changes in typescript typings for details have a look at this pull request.

v12.x.x to v13.0.0

  • typescript definitions now can directly be used from the i18next module - no longer needed to get them from DefinitelyTyped

  • functions used to return a callback (eg. init, changeLanguage, loadNamespaces) now also return a Promise - while this enables easier handling using async await this also means eg. i18next.init does not return this anylonger and therefore you can't chain calls like i18next.init().on() anylonger.

v11.x.x to v12.0.0

v10.x.x to v11.0.0

v9.x.x to v10.0.0

brings pt, pt-PT, pt-BR plurals in line with, new pt reflects pt-BR and pt-PT gets a special case for plural handling http://www.unicode.org/cldr/charts/26/supplemental/language_plural_rules.html



Portugal Portuguese

plurals=2; plural=(n != 1);


Brazilian Portuguese

plurals=2; plural=(n > 1);



plurals=2; plural=(n > 1);

v8.x.x to v9.0.0

With v9 we removed the compatibility for the v1 API. So the compatibilityAPI: 'v1' flag won't do anything anymore.

You still can append this manually as we do for our old v1 tests - learn more.

v7.x.x to v8.0.0

The nonExplicitWhitelist flag was changed to be used in user detected language too, before it was restricted to defined fallback languages only.

  fallbackLng: 'en',
  whitelist: ['de', 'en', 'zh'],
  nonExplicitWhitelist: true

// eg. `de-AT` will now pass the whitelist check

v6.x.x to v7.0.0

We used to resolve nb-NO, nn-NO to no as language part mainly because there was no way to proper define per local fallbacks. With v7.0.0 we removed that to enable default behaviour also for norwegian language. To get back the old behaviour you can define multiple fallbacks like:

fallbackLng: {
  'nb': ['no', 'en'],
  'nn': ['no', 'en'],
  'default': ['en']

Additional starting from 7.0.0 you could use named exports:

import { init, t } from 'i18next';

v5.x.x to v6.0.0

Return namespace in cimode with appendNamespaceToCIMode option (default now will only return key without namespace - independent of call to t function) #863

This change might break your e2e tests if your depending on the cimode (the returned value can now be set to return always only key or ns+key)

v4.x.x to v5.0.0

Nested keys should not be escaped #854

i18next.cloneInstance() calls now init() (before it depended on having called that function with a callback) #860

v3.x.x to v4.0.0

There is only a small change for webpack2 builds which now targets es build with import/export in place to enable treeshaking (module entrypoint in package.json).

Nothing breaking for non webpack2 users.

v2.x.x to v3.0.0

There is one breaking change regarding suffixing plurals in cases a language has multiple plural forms. Eg. arabic suffixes are now 0, 1, 2, 3, 4, 5 instead of 0, 1, 2, 3, 11, 100.

This change streamlines the suffix with the one used in gettext.

To enforce old behaviour you can enable compatibilityJSON = 'v2' on i18next init call.

import i18next from 'i18next';

  compatibilityJSON: 'v2'
}, (err, t) => { /* resources are loaded */ });

v1.11.x to v2.0.0

While v2.0.0 is a full rewrite of the old codebase it should be possible to run in your app without completely rewrite your integration.

Getting started

The new version does not come with backend, cache and user language detection built in. i18next is more a core library that can be extended with modules on demand. This way it can be seamlessly used in browser, node.js or other javascript runtimes.

Modules are available on npm, via bower or on github to download.


import i18next from 'i18next';
import XHR from 'i18next-xhr-backend';
import Cache from 'i18next-localstorage-cache';
import sprintf from 'i18next-sprintf-postprocessor';
import LanguageDetector from 'i18next-browser-languagedetector';

  .init(options, callback);

hint for jquery user: use additional jquery-i18next


var i18next = require('i18next'),
  FilesystemBackend = require('i18next-node-fs-backend'),
  sprintf = require('i18next-sprintf-postprocessor');

  .init(options, callback);

nodejs + express

var express = require('express');
  i18next = require('i18next'),
  FilesystemBackend = require('i18next-node-fs-backend'),
  sprintf = require('i18next-sprintf-postprocessor'),
  i18nextMiddleware = require('i18next-express-middleware');

  .init(options, callback);

var app = express();

app.use(i18nextMiddleware.handle(i18next)); // expose req.t with fixed lng
app.post('/locales/add/:lng/:ns', i18nextMiddleware.missingKeyHandler(i18next)); // serves missing key route for consumers (browser)
app.get('/locales/resources.json', i18nextMiddleware.getResourcesHandler(i18next)); // serves resources for consumers (browser)


Running v2.0.0 with compatibility flags

Version 2.0.0 has a compatibility layer built in which allows to run it like v1.11.x. Keep in mind this layer will be removed in future version.

import i18next from 'i18next';

  compatibilityAPI: 'v1',
  compatibilityJSON: 'v1',
  // ...old options from v1
}, (err, t) => { /* resources are loaded */ });


Will convert init and t options and expose old API functions. Will be removed with future update.


Will allow to use JSON files in v1 format. Using old interpolation prefix, suffix and no need for singular suffix [0] for singular in languages with more then just 1 plural form.

Not supported any longer in v2.0.0

  • support for older browsers:

    Beginning with v2 we target only modern browsers (Chrome, Firefox, ... and IE >= 10).

    For IE9 you will need to add a es5 shim

  • jquery:

    use additional jquery-i18next

  • synchronous loading:

    i18next.init({ getAsync: false });

    is not supported any longer - as not encouraged by browsers.

  • no conflict:


    was removed as i18next registers to window.i18next and no longer to window.i18n

  • indefinite article:

    i18n.t('myKey', { indefinite_article: true })

    was removed - as the solution was too limited - reconsidering adding a better solution in a future v2 release

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