Didn't work with defaultLanguage different than en?

server.js

app.prepare().then(() => {
    const server = express();

    if (!dev) {
        server.use(compression({threshold: 0}));
    }

    nextI18NextMiddleware(app, server);
...

i18n.js

module.exports = new NextI18Next({
  defaultLanguage: 'mn',
  otherLanguages: ['en'],
});

My App starts with en not mn

[ahmedengu]

I was able to resolve this issue by removing ‘header’ from detectors by adding the following to my config to override the default detectors:

detection: {
    lookupCookie: 'next-i18next',
    order: ['cookie', 'querystring', 'localStorage', 'path', 'subdomain'],
    caches: ['cookie'],
  },

so the set up would be:

import NextI18Next from 'next-i18next'

const NextI18NextInstance = new NextI18Next({
  defaultLanguage: 'ar',
  otherLanguages: ['de'],
  detection: {
    lookupCookie: 'next-i18next',
    order: ['cookie', 'querystring', 'localStorage', 'path', 'subdomain'],
    caches: ['cookie'],
  },
})

export default NextI18NextInstance

/* Optionally, export class methods as named exports */
export const {
  appWithTranslation,
  withTranslation,
} = NextI18NextInstance

the header detector check the request headers for accept-language which is en in most cases

[elyash14]

Hello everyone. but I had this problem and when I changed my default language to something like “fa” in the config, nothing happened and the “en” json file was loaded. I didn’t have any custom server like server.js and after some search and playing with NextI18Next configs, set serverLanguageDetection option to false and everything worked properly. new NextI18Next({ defaultLanguage: 'fa', otherLanguages: ['en'], defaultNS: 'agro', localePath: path.resolve('./public/locales'), debug: true, browserLanguageDetection: true, serverLanguageDetection: false, });