diff --git a/src/main/configStore.ts b/src/main/configStore.ts
index c360b05d..a1833ccc 100644
--- a/src/main/configStore.ts
+++ b/src/main/configStore.ts
@@ -9,6 +9,7 @@ import { copyFile } from 'node:fs/promises';
 import { KeyBinding, Config } from '../../types.js';
 import logger from './logger.js';
 import { isWindows } from './util.js';
+import { fallbackLng } from './i18nCommon.js';
 
 const { app } = electron;
 
@@ -117,7 +118,7 @@ const defaults: Config = {
   autoSaveProjectFile: true,
   wheelSensitivity: 0.2,
   waveformHeight: 40,
-  language: undefined,
+  language: fallbackLng,
   ffmpegExperimental: false,
   preserveChapters: true,
   preserveMetadata: 'default',
diff --git a/src/main/i18n.ts b/src/main/i18n.ts
index 12417aab..3053f5b5 100644
--- a/src/main/i18n.ts
+++ b/src/main/i18n.ts
@@ -1,5 +1,7 @@
 import i18n from 'i18next';
 import Backend from 'i18next-fs-backend';
+// eslint-disable-next-line import/no-extraneous-dependencies
+import { app } from 'electron';
 
 import { commonI18nOptions, loadPath, addPath } from './i18nCommon.js';
 
@@ -8,12 +10,7 @@ import { commonI18nOptions, loadPath, addPath } from './i18nCommon.js';
 // https://github.com/i18next/i18next/issues/869
 export default i18n
   .use(Backend)
-  // detect user language
-  // learn more: https://github.com/i18next/i18next-browser-languageDetector
-  // TODO disabled for now because translations need more reviewing https://github.com/mifi/lossless-cut/issues/346
-  // .use(LanguageDetector)
-  // init i18next
-  // for all options read: https://www.i18next.com/overview/configuration-options
+  .use({ type: 'languageDetector', async: false, detect: () => app.getLocale() })
   // See also i18next-parser.config.mjs
   .init({
     ...commonI18nOptions,
diff --git a/src/main/i18nCommon.ts b/src/main/i18nCommon.ts
index 11a06c60..dbb866e8 100644
--- a/src/main/i18nCommon.ts
+++ b/src/main/i18nCommon.ts
@@ -4,6 +4,7 @@
 import { app } from 'electron';
 import { join } from 'node:path';
 import { InitOptions } from 'i18next';
+import { ElectronLanguageKey, SupportedLanguage } from '../../types';
 
 
 let customLocalesPath: string | undefined;
@@ -20,22 +21,47 @@ function getLangPath(subPath: string) {
 // Weblate hardcodes different lang codes than electron
 // https://www.electronjs.org/docs/api/app#appgetlocale
 // https://source.chromium.org/chromium/chromium/src/+/master:ui/base/l10n/l10n_util.cc
-const mapLang = (lng: string) => ({
-  nb: 'nb_NO',
-  no: 'nb_NO',
-  zh: 'zh_Hans',
-  // https://source.chromium.org/chromium/chromium/src/+/master:ui/base/l10n/l10n_util.cc;l=354
-  'zh-CN': 'zh_Hans', // Chinese simplified (mainland China)
-  'zh-TW': 'zh_Hant', // Chinese traditional (Taiwan)
-  fr: 'fr',
-  'fr-CA': 'fr',
-  'fr-CH': 'fr',
-  'fr-FR': 'fr',
-  it: 'it',
-  'it-CH': 'it',
-  'it-IT': 'it',
-  'ru-RU': 'ru',
-}[lng] || lng);
+function mapLang(lng: ElectronLanguageKey) {
+  const map: Partial<Record<ElectronLanguageKey, string>> = {
+    'de-AT': 'de',
+    'de-CH': 'de',
+    'de-DE': 'de',
+    'de-LI': 'de',
+
+    'es-419': 'es',
+    'es-AR': 'es',
+    'es-CL': 'es',
+    'es-CO': 'es',
+    'es-CR': 'es',
+    'es-ES': 'es',
+    'es-HN': 'es',
+    'es-MX': 'es',
+    'es-PE': 'es',
+    'es-US': 'es',
+    'es-UY': 'es',
+    'es-VE': 'es',
+
+    'fr-CA': 'fr',
+    'fr-CH': 'fr',
+    'fr-FR': 'fr',
+
+    nb: 'nb_NO',
+    no: 'nb_NO',
+
+    zh: 'zh_Hans',
+    'zh-CN': 'zh_Hans',
+    'zh-TW': 'zh_Hant',
+    'zh-HK': 'zh_Hant',
+
+    'pt-BR': 'pt_BR',
+    'pt-PT': 'pt',
+
+    'it-CH': 'it',
+    'it-IT': 'it',
+  };
+
+  return map[lng] ?? lng;
+}
 
 export const fallbackLng = 'en';
 
@@ -53,5 +79,5 @@ export const commonI18nOptions: InitOptions = {
   nsSeparator: false,
 };
 
-export const loadPath = (lng: string, ns: string) => getLangPath(`${mapLang(lng)}/${ns}.json`);
-export const addPath = (lng: string, ns: string) => getLangPath(`${mapLang(lng)}/${ns}.missing.json`);
+export const loadPath = (lng: SupportedLanguage, ns: string) => getLangPath(`${mapLang(lng)}/${ns}.json`);
+export const addPath = (lng: SupportedLanguage, ns: string) => getLangPath(`${mapLang(lng)}/${ns}.missing.json`);
diff --git a/src/renderer/src/App.tsx b/src/renderer/src/App.tsx
index 6e799f17..3ed0882a 100644
--- a/src/renderer/src/App.tsx
+++ b/src/renderer/src/App.tsx
@@ -80,7 +80,6 @@ import { adjustRate } from './util/rate-calculator';
 import { askExtractFramesAsImages } from './dialogs/extractFrames';
 import { askForOutDir, askForImportChapters, askForFileOpenAction, showDiskFull, showExportFailedDialog, showConcatFailedDialog, openYouTubeChaptersDialog, showRefuseToOverwrite, showOpenDialog, showMuxNotSupported, promptDownloadMediaUrl, CleanupChoicesType, showOutputNotWritable, deleteFiles, mustDisallowVob, toastError } from './dialogs';
 import { openSendReportDialog } from './reporting';
-import { fallbackLng } from './i18n';
 import { sortSegments, convertSegmentsToChaptersWithGaps, hasAnySegmentOverlap, isDurationValid, getPlaybackAction, getSegmentTags, filterNonMarkers } from './segments';
 import { generateCutFileNames as generateCutFileNamesRaw, generateCutMergedFileNames as generateCutMergedFileNamesRaw, generateMergedFileNames as generateMergedFileNamesRaw, defaultCutFileTemplate, defaultCutMergedFileTemplate, defaultMergedFileTemplate, GenerateMergedOutFileNamesParams, GeneratedOutFileNames } from './util/outputNameTemplate';
 import { rightBarWidth, leftBarWidth, ffmpegExtractWindow, zoomMax } from './util/constants';
@@ -204,9 +203,8 @@ function App() {
   const mergedFileTemplateOrDefault = mergedFileTemplate || defaultMergedFileTemplate;
 
   useEffect(() => {
-    const l = language || fallbackLng;
-    i18n.changeLanguage(l).catch(console.error);
-    electron.ipcRenderer.send('setLanguage', l);
+    i18n.changeLanguage(language).catch(console.error);
+    electron.ipcRenderer.send('setLanguage', language);
   }, [language]);
 
 
diff --git a/src/renderer/src/components/ConcatSheet.tsx b/src/renderer/src/components/ConcatSheet.tsx
index eaa50a58..ab738e47 100644
--- a/src/renderer/src/components/ConcatSheet.tsx
+++ b/src/renderer/src/components/ConcatSheet.tsx
@@ -103,7 +103,6 @@ function ConcatSheet({ isShown, onHide, paths, mergedFileTemplate, generateMerge
 
   useEffect(() => {
     const abortController = new AbortController();
-    console.log('wat', fileFormat);
 
     (async () => {
       // in simple mode, set merged file template to a generated name based on first file, so they don't *have to* deal with variables
diff --git a/src/renderer/src/components/Settings.tsx b/src/renderer/src/components/Settings.tsx
index 3c6ccef4..857c4d7e 100644
--- a/src/renderer/src/components/Settings.tsx
+++ b/src/renderer/src/components/Settings.tsx
@@ -10,7 +10,7 @@ import Switch from './Switch';
 import useUserSettings from '../hooks/useUserSettings';
 import { askForFfPath } from '../dialogs';
 import { isMasBuild, isStoreBuild } from '../util';
-import { Config, LanguageKey, ModifierKey, TimecodeFormat, langNames } from '../../../../types';
+import { Config, SupportedLanguage, ModifierKey, TimecodeFormat, langNames } from '../../../../types';
 import styles from './Settings.module.css';
 import SelectRaw, { SelectProps } from './Select';
 import ButtonRaw, { ButtonProps } from './Button';
@@ -74,7 +74,7 @@ function Settings({
   const onLangChange = useCallback<ChangeEventHandler<HTMLSelectElement>>((e) => {
     const { value } = e.target;
     const l = value !== '' ? value : undefined;
-    setLanguage(l as LanguageKey | undefined);
+    setLanguage(l as SupportedLanguage | undefined);
   }, [setLanguage]);
 
   const timecodeFormatOptions = useMemo<Record<TimecodeFormat, string>>(() => ({
diff --git a/src/renderer/src/i18n.ts b/src/renderer/src/i18n.ts
index dbad35f7..dc91fdb4 100644
--- a/src/renderer/src/i18n.ts
+++ b/src/renderer/src/i18n.ts
@@ -3,29 +3,18 @@ import { initReactI18next } from 'react-i18next';
 
 const Backend = window.require('i18next-fs-backend');
 
-const { i18n: { commonI18nOptions, fallbackLng, loadPath, addPath } } = window.require('@electron/remote').require('./index.js');
+const remote = window.require('@electron/remote');
+const { i18n: { commonI18nOptions, loadPath, addPath } } = remote.require('./index.js');
 
-// https://www.i18next.com/overview/typescript#argument-of-type-defaulttfuncreturn-is-not-assignable-to-parameter-of-type-xyz
-// todo This should not be necessary anymore since v23.0.0
-declare module 'i18next' {
-  interface CustomTypeOptions {
-    returnNull: false;
-  }
-}
-export { fallbackLng };
+
+// See also main
 
 // https://github.com/i18next/react-i18next/blob/master/example/react/src/i18n.js
 // https://github.com/i18next/i18next/issues/869
 i18n
   .use(Backend)
-  // detect user language
-  // learn more: https://github.com/i18next/i18next-browser-languageDetector
-  // LanguageDetector is disabled because many users are used to english, and I cannot guarantee the status of all the translations so it's best to default to engligh https://github.com/mifi/lossless-cut/issues/346
-  // .use(LanguageDetector)
-  // pass the i18n instance to react-i18next.
+  .use({ type: 'languageDetector', async: false, detect: () => remote.app.getLocale() })
   .use(initReactI18next)
-  // init i18next
-  // for all options read: https://www.i18next.com/overview/configuration-options
   // See also i18next-parser.config.mjs
   .init({
     ...commonI18nOptions,
diff --git a/types.ts b/types.ts
index f432a85d..355ad4bb 100644
--- a/types.ts
+++ b/types.ts
@@ -7,7 +7,197 @@ export interface KeyBinding {
 
 export type CaptureFormat = 'jpeg' | 'png' | 'webp';
 
-// https://www.electronjs.org/docs/api/locales
+// returned from app.getLocale()
+// https://www.electronjs.org/docs/api/app#appgetlocale
+// https://source.chromium.org/chromium/chromium/src/+/master:ui/base/l10n/l10n_util.cc
+export type ElectronLanguageKey =
+'af' // Afrikaans
+| 'ak' // Twi
+| 'am' // Amharic
+| 'an' // Aragonese
+| 'ar' // Arabic
+| 'as' // Assamese
+| 'ast' // Asturian
+| 'ay' // Aymara
+| 'az' // Azerbaijani
+| 'be' // Belarusian
+| 'bg' // Bulgarian
+| 'bho' // Bhojpuri
+| 'bm' // Bambara
+| 'bn' // Bengali
+| 'br' // Breton
+| 'bs' // Bosnian
+| 'ca' // Catalan
+| 'ceb' // Cebuano
+| 'chr' // Cherokee
+| 'ckb' // Kurdish (Arabic),  Sorani
+| 'co' // Corsican
+| 'cs' // Czech
+| 'cy' // Welsh
+| 'da' // Danish
+| 'de' // German
+| 'de-AT' // German (Austria)
+| 'de-CH' // German (Switzerland)
+| 'de-DE' // German (Germany)
+| 'de-LI' // German (Liechtenstein)
+| 'doi' // Dogri
+| 'dv' // Dhivehi
+| 'ee' // Ewe
+| 'el' // Greek
+| 'en' // English
+| 'en-AU' // English (Australia)
+| 'en-CA' // English (Canada)
+| 'en-GB' // English (UK)
+| 'en-GB-oxendict' // English (UK, OED spelling)
+| 'en-IE' // English (Ireland)
+| 'en-IN' // English (India)
+| 'en-NZ' // English (New Zealand)
+| 'en-US' // English (US)
+| 'en-ZA' // English (South Africa)
+| 'eo' // Esperanto
+| 'es' // Spanish
+| 'es-419' // Spanish (Latin America)
+| 'es-AR' // Spanish (Argentina)
+| 'es-CL' // Spanish (Chile)
+| 'es-CO' // Spanish (Colombia)
+| 'es-CR' // Spanish (Costa Rica)
+| 'es-ES' // Spanish (Spain)
+| 'es-HN' // Spanish (Honduras)
+| 'es-MX' // Spanish (Mexico)
+| 'es-PE' // Spanish (Peru)
+| 'es-US' // Spanish (US)
+| 'es-UY' // Spanish (Uruguay)
+| 'es-VE' // Spanish (Venezuela)
+| 'et' // Estonian
+| 'eu' // Basque
+| 'fa' // Persian
+| 'fi' // Finnish
+| 'fil' // Filipino
+| 'fo' // Faroese
+| 'fr' // French
+| 'fr-CA' // French (Canada)
+| 'fr-CH' // French (Switzerland)
+| 'fr-FR' // French (France)
+| 'fy' // Frisian
+| 'ga' // Irish
+| 'gd' // Scots Gaelic
+| 'gl' // Galician
+| 'gn' // Guarani
+| 'gu' // Gujarati
+| 'ha' // Hausa
+| 'haw' // Hawaiian
+| 'he' // Hebrew
+| 'hi' // Hindi
+| 'hmn' // Hmong
+| 'hr' // Croatian
+| 'ht' // Haitian Creole
+| 'hu' // Hungarian
+| 'hy' // Armenian
+| 'ia' // Interlingua
+| 'id' // Indonesian
+| 'ig' // Igbo
+| 'ilo' // Ilocano
+| 'is' // Icelandic
+| 'it' // Italian
+| 'it-CH' // Italian (Switzerland)
+| 'it-IT' // Italian (Italy)
+| 'ja' // Japanese
+| 'jv' // Javanese
+| 'ka' // Georgian
+| 'kk' // Kazakh
+| 'km' // Cambodian
+| 'kn' // Kannada
+| 'ko' // Korean
+| 'kok' // Konkani
+| 'kri' // Krio
+| 'ku' // Kurdish
+| 'ky' // Kyrgyz
+| 'la' // Latin
+| 'lb' // Luxembourgish
+| 'lg' // Luganda
+| 'ln' // Lingala
+| 'lo' // Laothian
+| 'lt' // Lithuanian
+| 'lus' // Mizo
+| 'lv' // Latvian
+| 'mai' // Maithili
+| 'mg' // Malagasy
+| 'mi' // Maori
+| 'mk' // Macedonian
+| 'ml' // Malayalam
+| 'mn' // Mongolian
+| 'mni-Mtei' // Manipuri (Meitei Mayek)
+| 'mo' // Moldavian
+| 'mr' // Marathi
+| 'ms' // Malay
+| 'mt' // Maltese
+| 'my' // Burmese
+| 'nb' // Norwegian (Bokmal)
+| 'ne' // Nepali
+| 'nl' // Dutch
+| 'nn' // Norwegian (Nynorsk)
+| 'no' // Norwegian
+| 'nso' // Sepedi
+| 'ny' // Nyanja
+| 'oc' // Occitan
+| 'om' // Oromo
+| 'or' // Odia (Oriya)
+| 'pa' // Punjabi
+| 'pl' // Polish
+| 'ps' // Pashto
+| 'pt' // Portuguese
+| 'pt-BR' // Portuguese (Brazil)
+| 'pt-PT' // Portuguese (Portugal)
+| 'qu' // Quechua
+| 'rm' // Romansh
+| 'ro' // Romanian
+| 'ru' // Russian
+| 'rw' // Kinyarwanda
+| 'sa' // Sanskrit
+| 'sd' // Sindhi
+| 'sh' // Serbo-Croatian
+| 'si' // Sinhalese
+| 'sk' // Slovak
+| 'sl' // Slovenian
+| 'sm' // Samoan
+| 'sn' // Shona
+| 'so' // Somali
+| 'sq' // Albanian
+| 'sr' // Serbian
+| 'st' // Sesotho
+| 'su' // Sundanese
+| 'sv' // Swedish
+| 'sw' // Swahili
+| 'ta' // Tamil
+| 'te' // Telugu
+| 'tg' // Tajik
+| 'th' // Thai
+| 'ti' // Tigrinya
+| 'tk' // Turkmen
+| 'tn' // Tswana
+| 'to' // Tonga
+| 'tr' // Turkish
+| 'ts' // Tsonga
+| 'tt' // Tatar
+| 'tw' // Twi
+| 'ug' // Uyghur
+| 'uk' // Ukrainian
+| 'ur' // Urdu
+| 'uz' // Uzbek
+| 'vi' // Vietnamese
+| 'wa' // Walloon
+| 'wo' // Wolof
+| 'xh' // Xhosa
+| 'yi' // Yiddish
+| 'yo' // Yoruba
+| 'zh' // Chinese
+| 'zh-CN' // Chinese (China)
+| 'zh-HK' // Chinese (Hong Kong)
+| 'zh-TW' // Chinese (Taiwan)
+| 'zu' // Zulu
+
+// https://www.electronjs.org/docs/api/app#appgetlocale
+// https://source.chromium.org/chromium/chromium/src/+/master:ui/base/l10n/l10n_util.cc
 // See i18n.js
 export const langNames = {
   en: 'English',
@@ -21,23 +211,25 @@ export const langNames = {
   nn: 'Norsk (nynorsk)',
   pl: 'Polski',
   pt: 'Português',
-  pt_BR: 'Português do Brasil',
+  'pt-BR': 'Português do Brasil',
   sl: 'Slovenščina',
-  sk: 'slovenčina',
+  sk: 'Slovenčina',
   fi: 'Suomi',
   ru: 'Русский',
-  uk: 'українська',
+  uk: 'Українська',
   // sr: 'Cрпски',
   tr: 'Türkçe',
   vi: 'Tiếng Việt',
   ja: '日本語',
   zh: '中文',
-  zh_Hant: '繁體中文',
-  zh_Hans: '简体中文',
+  'zh-TW': '繁體中文',
+  'zh-CN': '简体中文',
   ko: '한국어',
-};
+} satisfies Partial<Record<ElectronLanguageKey, string>>;
+
+type ExtraLanguages = 'no';
 
-export type LanguageKey = keyof typeof langNames;
+export type SupportedLanguage = (keyof typeof langNames) | ExtraLanguages;
 
 export type TimecodeFormat = 'timecodeWithDecimalFraction' | 'frameCount' | 'seconds' | 'timecodeWithFramesFraction';
 
@@ -73,7 +265,7 @@ export interface Config {
   autoSaveProjectFile: boolean,
   wheelSensitivity: number,
   waveformHeight: number,
-  language: LanguageKey | undefined,
+  language: SupportedLanguage | undefined,
   ffmpegExperimental: boolean,
   preserveChapters: boolean,
   preserveMetadata: PreserveMetadata,