diff --git a/_scripts/getRegions.mjs b/_scripts/getRegions.mjs
index 482b20470..842bd7cb1 100644
--- a/_scripts/getRegions.mjs
+++ b/_scripts/getRegions.mjs
@@ -46,13 +46,6 @@ for (const language of youTubeLanguages) {
       youTube: language,
       freeTube: language
     })
-  } else if (activeLanguages.includes(language.replace('-', '_'))) {
-    const withUnderScore = language.replace('-', '_')
-    foundLanguageNames.push(withUnderScore)
-    languagesToScrape.push({
-      youTube: language,
-      freeTube: withUnderScore
-    })
   }
   // special cases
   else if (language === 'de') {
@@ -70,10 +63,10 @@ for (const language of youTubeLanguages) {
   } else if (language === 'no') {
     // according to https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
     // "no" is the macro language for "nb" and "nn"
-    foundLanguageNames.push('nb_NO', 'nn')
+    foundLanguageNames.push('nb-NO', 'nn')
     languagesToScrape.push({
       youTube: 'no',
-      freeTube: 'nb_NO'
+      freeTube: 'nb-NO'
     })
     languagesToScrape.push({
       youTube: 'no',
@@ -88,10 +81,10 @@ for (const language of youTubeLanguages) {
       freeTube: 'he'
     })
   } else if (language === 'es-419') {
-    foundLanguageNames.push('es_AR', 'es-MX')
+    foundLanguageNames.push('es-AR', 'es-MX')
     languagesToScrape.push({
       youTube: 'es-419',
-      freeTube: 'es_AR'
+      freeTube: 'es-AR'
     })
     languagesToScrape.push({
       youTube: 'es-419',
diff --git a/_scripts/getShakaLocales.js b/_scripts/getShakaLocales.js
index 5e495bcd3..5beb42407 100644
--- a/_scripts/getShakaLocales.js
+++ b/_scripts/getShakaLocales.js
@@ -41,15 +41,10 @@ function getMappings(shakaLocales, freeTubeLocales) {
         locale,
         locale
       ])
-    } else if (shakaLocales.has(locale.replace('_', '-'))) {
+    } else if (shakaLocales.has(locale.split('-')[0])) {
       mappings.push([
         locale,
-        locale.replace('_', '-')
-      ])
-    } else if (shakaLocales.has(locale.split(/[-_]/)[0])) {
-      mappings.push([
-        locale,
-        locale.split(/[-_]/)[0]
+        locale.split('-')[0]
       ])
     }
   }
@@ -60,7 +55,7 @@ function getMappings(shakaLocales, freeTubeLocales) {
     // according to https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
     // "no" is the macro language for "nb" and "nn"
     [
-      'nb_NO',
+      'nb-NO',
       'no'
     ],
     [
diff --git a/src/datastores/handlers/base.js b/src/datastores/handlers/base.js
index 32457d3c9..614b21cd2 100644
--- a/src/datastores/handlers/base.js
+++ b/src/datastores/handlers/base.js
@@ -1,7 +1,15 @@
 import * as db from '../index'
 
 class Settings {
-  static find() {
+  static async find() {
+    const currentLocale = await db.settings.findOneAsync({ _id: 'currentLocale' })
+
+    // In FreeTube 0.21.3 and earlier the locales 'en-GB', 'es-AR' and 'nb-NO' had underscores instead of a hyphens
+    // This is a one time migration for users that are using one of those locales
+    if (currentLocale?.value.includes('_')) {
+      await this.upsert('currentLocale', currentLocale.value.replace('_', '-'))
+    }
+
     return db.settings.findAsync({ _id: { $ne: 'bounds' } })
   }
 
diff --git a/src/renderer/App.js b/src/renderer/App.js
index 0308944cb..36611d193 100644
--- a/src/renderer/App.js
+++ b/src/renderer/App.js
@@ -122,7 +122,7 @@ export default defineComponent({
     },
 
     locale: function() {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     systemTheme: function () {
diff --git a/src/renderer/components/channel-about/channel-about.js b/src/renderer/components/channel-about/channel-about.js
index 3eb151e1b..4e5360e47 100644
--- a/src/renderer/components/channel-about/channel-about.js
+++ b/src/renderer/components/channel-about/channel-about.js
@@ -55,7 +55,7 @@ export default defineComponent({
     },
 
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     formattedJoined: function () {
diff --git a/src/renderer/components/ft-list-video/ft-list-video.js b/src/renderer/components/ft-list-video/ft-list-video.js
index c90e1fa9c..cffc195fa 100644
--- a/src/renderer/components/ft-list-video/ft-list-video.js
+++ b/src/renderer/components/ft-list-video/ft-list-video.js
@@ -364,7 +364,7 @@ export default defineComponent({
     },
 
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     externalPlayer: function () {
diff --git a/src/renderer/components/ft-playlist-add-video-prompt/ft-playlist-add-video-prompt.js b/src/renderer/components/ft-playlist-add-video-prompt/ft-playlist-add-video-prompt.js
index 0753f7ff1..09fb1a20f 100644
--- a/src/renderer/components/ft-playlist-add-video-prompt/ft-playlist-add-video-prompt.js
+++ b/src/renderer/components/ft-playlist-add-video-prompt/ft-playlist-add-video-prompt.js
@@ -119,7 +119,7 @@ export default defineComponent({
       return this.$store.getters.getNewPlaylistDefaultProperties
     },
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     processedQuery: function() {
       return this.query.trim().toLowerCase()
diff --git a/src/renderer/components/ft-profile-bubble/ft-profile-bubble.js b/src/renderer/components/ft-profile-bubble/ft-profile-bubble.js
index 39d4e226e..c0926f978 100644
--- a/src/renderer/components/ft-profile-bubble/ft-profile-bubble.js
+++ b/src/renderer/components/ft-profile-bubble/ft-profile-bubble.js
@@ -26,7 +26,7 @@ export default defineComponent({
   emits: ['click'],
   computed: {
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     isMainProfile: function () {
       return this.profileId === MAIN_PROFILE_ID
diff --git a/src/renderer/components/ft-profile-channel-list/ft-profile-channel-list.js b/src/renderer/components/ft-profile-channel-list/ft-profile-channel-list.js
index c9b859008..96cefa269 100644
--- a/src/renderer/components/ft-profile-channel-list/ft-profile-channel-list.js
+++ b/src/renderer/components/ft-profile-channel-list/ft-profile-channel-list.js
@@ -66,7 +66,7 @@ export default defineComponent({
       ]
     },
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
   },
   watch: {
diff --git a/src/renderer/components/ft-profile-edit/ft-profile-edit.js b/src/renderer/components/ft-profile-edit/ft-profile-edit.js
index 5b9e5b439..a46a6d7d5 100644
--- a/src/renderer/components/ft-profile-edit/ft-profile-edit.js
+++ b/src/renderer/components/ft-profile-edit/ft-profile-edit.js
@@ -49,7 +49,7 @@ export default defineComponent({
   },
   computed: {
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     colorValues: function () {
       return colors.map(color => color.value)
diff --git a/src/renderer/components/ft-profile-filter-channels-list/ft-profile-filter-channels-list.js b/src/renderer/components/ft-profile-filter-channels-list/ft-profile-filter-channels-list.js
index 57beae3b2..b18f57b70 100644
--- a/src/renderer/components/ft-profile-filter-channels-list/ft-profile-filter-channels-list.js
+++ b/src/renderer/components/ft-profile-filter-channels-list/ft-profile-filter-channels-list.js
@@ -49,7 +49,7 @@ export default defineComponent({
       return this.$t('Profile.{number} selected', { number: this.selectedLength })
     },
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     }
   },
   watch: {
diff --git a/src/renderer/components/ft-profile-selector/ft-profile-selector.js b/src/renderer/components/ft-profile-selector/ft-profile-selector.js
index 3e8eeffeb..d9c519396 100644
--- a/src/renderer/components/ft-profile-selector/ft-profile-selector.js
+++ b/src/renderer/components/ft-profile-selector/ft-profile-selector.js
@@ -21,7 +21,7 @@ export default defineComponent({
   },
   computed: {
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     profileList: function () {
       return this.$store.getters.getProfileList
diff --git a/src/renderer/components/ft-select/ft-select.vue b/src/renderer/components/ft-select/ft-select.vue
index 77f466625..57e9a9a72 100644
--- a/src/renderer/components/ft-select/ft-select.vue
+++ b/src/renderer/components/ft-select/ft-select.vue
@@ -15,7 +15,7 @@
         v-for="(name, index) in selectNames"
         :key="index"
         :value="selectValues[index]"
-        :lang="isLocaleSelector && selectValues[index] !== 'system' ? selectValues[index].replace('_', '-') : null"
+        :lang="isLocaleSelector && selectValues[index] !== 'system' ? selectValues[index] : null"
       >
         {{ name }}
       </option>
diff --git a/src/renderer/components/ft-subscribe-button/ft-subscribe-button.js b/src/renderer/components/ft-subscribe-button/ft-subscribe-button.js
index da395dcb7..b0a0906e1 100644
--- a/src/renderer/components/ft-subscribe-button/ft-subscribe-button.js
+++ b/src/renderer/components/ft-subscribe-button/ft-subscribe-button.js
@@ -51,7 +51,7 @@ export default defineComponent({
   },
   computed: {
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     profileInitials: function () {
       return this.profileDisplayList.map((profile) => {
diff --git a/src/renderer/components/proxy-settings/proxy-settings.js b/src/renderer/components/proxy-settings/proxy-settings.js
index b985c39d6..901ca21d8 100644
--- a/src/renderer/components/proxy-settings/proxy-settings.js
+++ b/src/renderer/components/proxy-settings/proxy-settings.js
@@ -64,7 +64,7 @@ export default defineComponent({
       return `${this.proxyProtocol}://${this.proxyHostname}:${this.proxyPort}`
     },
     lang: function() {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     localeToUse: function() {
       // locales found here: https://ipwhois.io/documentation
diff --git a/src/renderer/components/side-nav/side-nav.js b/src/renderer/components/side-nav/side-nav.js
index dd050476b..45db9ef8e 100644
--- a/src/renderer/components/side-nav/side-nav.js
+++ b/src/renderer/components/side-nav/side-nav.js
@@ -30,7 +30,7 @@ export default defineComponent({
       return this.$store.getters.getActiveProfile
     },
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     activeSubscriptions: function () {
       const subscriptions = deepCopy(this.activeProfile.subscriptions)
diff --git a/src/renderer/components/subscriptions-videos/subscriptions-videos.js b/src/renderer/components/subscriptions-videos/subscriptions-videos.js
index d3457e22f..c7ed19f28 100644
--- a/src/renderer/components/subscriptions-videos/subscriptions-videos.js
+++ b/src/renderer/components/subscriptions-videos/subscriptions-videos.js
@@ -45,7 +45,7 @@ export default defineComponent({
     },
 
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     lastVideoRefreshTimestamp: function () {
diff --git a/src/renderer/components/watch-video-info/watch-video-info.js b/src/renderer/components/watch-video-info/watch-video-info.js
index ed57aa9f2..ef5cf85c6 100644
--- a/src/renderer/components/watch-video-info/watch-video-info.js
+++ b/src/renderer/components/watch-video-info/watch-video-info.js
@@ -119,7 +119,7 @@ export default defineComponent({
     },
 
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     hideVideoLikesAndDislikes: function () {
diff --git a/src/renderer/components/watch-video-playlist/watch-video-playlist.js b/src/renderer/components/watch-video-playlist/watch-video-playlist.js
index ec0ccd27c..bfe449b6e 100644
--- a/src/renderer/components/watch-video-playlist/watch-video-playlist.js
+++ b/src/renderer/components/watch-video-playlist/watch-video-playlist.js
@@ -68,7 +68,7 @@ export default defineComponent({
       return this.$store.getters.getBackendFallback
     },
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     isUserPlaylist: function () {
       return this.playlistType === 'user'
diff --git a/src/renderer/helpers/player/utils.js b/src/renderer/helpers/player/utils.js
index 8085d87cb..939423d16 100644
--- a/src/renderer/helpers/player/utils.js
+++ b/src/renderer/helpers/player/utils.js
@@ -139,7 +139,7 @@ export function qualityLabelToDimension(qualityLabel) {
  * }[]} captions
  */
 export function sortCaptions(captions) {
-  const currentLocale = i18n.locale.replace('_', '-')
+  const currentLocale = i18n.locale
   const userLocale = currentLocale.split('-') // ex. [en,US]
 
   const collator = new Intl.Collator([currentLocale, 'en'])
diff --git a/src/renderer/helpers/utils.js b/src/renderer/helpers/utils.js
index 08203d0b6..79c836930 100644
--- a/src/renderer/helpers/utils.js
+++ b/src/renderer/helpers/utils.js
@@ -12,10 +12,6 @@ export const CHANNEL_HANDLE_REGEX = /^@[\w.-]{3,30}$/
 
 const PUBLISHED_TEXT_REGEX = /(\d+)\s?([a-z]+)/i
 
-function currentLocale () {
-  return i18n.locale.replace('_', '-')
-}
-
 export function getIconForSortPreference(sortPreference) {
   switch (sortPreference) {
     case 'name_descending':
@@ -701,7 +697,7 @@ export function toDistractionFreeTitle(title, minUpperCase = 3) {
 }
 
 export function formatNumber(number, options = undefined) {
-  return Intl.NumberFormat([i18n.locale.replace('_', '-'), 'en'], options).format(number)
+  return Intl.NumberFormat([i18n.locale, 'en'], options).format(number)
 }
 
 export function getTodayDateStrLocalTimezone() {
@@ -767,7 +763,7 @@ export function getRelativeTimeFromDate(date, hideSeconds = false, useThirtyDayM
 
   // Using `Math.ceil` so that -1.x days ago displayed as 1 day ago
   // Notice that the value is turned to negative to be displayed as "ago"
-  return new Intl.RelativeTimeFormat([currentLocale(), 'en']).format(Math.ceil(-timeDiffFromNow), timeUnit)
+  return new Intl.RelativeTimeFormat([i18n.locale, 'en']).format(Math.ceil(-timeDiffFromNow), timeUnit)
 }
 
 /**
diff --git a/src/renderer/i18n/index.js b/src/renderer/i18n/index.js
index 3feed824a..555a3994b 100644
--- a/src/renderer/i18n/index.js
+++ b/src/renderer/i18n/index.js
@@ -11,8 +11,8 @@ const i18n = new VueI18n({
   fallbackLocale: {
     // https://kazupon.github.io/vue-i18n/guide/fallback.html#explicit-fallback-with-decision-maps
 
-    // es_AR -> es -> en-US
-    es_AR: ['es'],
+    // es-AR -> es -> en-US
+    'es-AR': ['es'],
     // es-MX -> es -> en-US
     'es-MX': ['es'],
     // pt-BR -> pt -> en-US
diff --git a/src/renderer/store/modules/settings.js b/src/renderer/store/modules/settings.js
index 2f223954e..1c657507a 100644
--- a/src/renderer/store/modules/settings.js
+++ b/src/renderer/store/modules/settings.js
@@ -316,17 +316,15 @@ const stateWithSideEffects = {
 
       let targetLocale = value
       if (value === 'system') {
-        const systemLocaleName = (await getSystemLocale()).replace('-', '_') // ex: en_US
-        const systemLocaleSplit = systemLocaleName.split('_') // ex: en
+        const systemLocaleName = (await getSystemLocale()).replace('_', '-') // ex: en-US
+        const systemLocaleSplit = systemLocaleName.split('-') // ex: en
         const targetLocaleOptions = allLocales.filter((locale) => {
           // filter out other languages
-          const localeLang = locale.replace('-', '_').split('_')[0]
+          const localeLang = locale.split('-')[0]
           return localeLang.includes(systemLocaleSplit[0])
-        }).sort((a, b) => {
-          const aLocaleName = a.replace('-', '_')
-          const bLocaleName = b.replace('-', '_')
-          const aLocale = aLocaleName.split('_') // ex: [en, US]
-          const bLocale = bLocaleName.split('_')
+        }).sort((aLocaleName, bLocaleName) => {
+          const aLocale = aLocaleName.split('-') // ex: [en, US]
+          const bLocale = bLocaleName.split('-')
 
           if (aLocaleName === systemLocaleName) { // country & language match, prefer a
             return -1
@@ -362,8 +360,8 @@ const stateWithSideEffects = {
         )
       }
 
-      // "es" is used as a fallback for "es_AR" and "es-MX"
-      if (targetLocale === 'es_AR' || targetLocale === 'es-MX') {
+      // "es" is used as a fallback for "es-AR" and "es-MX"
+      if (targetLocale === 'es-AR' || targetLocale === 'es-MX') {
         loadPromises.push(
           loadLocale('es')
         )
diff --git a/src/renderer/views/Playlist/Playlist.js b/src/renderer/views/Playlist/Playlist.js
index 91be3039b..8121a626f 100644
--- a/src/renderer/views/Playlist/Playlist.js
+++ b/src/renderer/views/Playlist/Playlist.js
@@ -97,7 +97,7 @@ export default defineComponent({
       return this.isUserPlaylistRequested ? this.userPlaylistSortOrder : SORT_BY_VALUES.Custom
     },
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     playlistId: function() {
       return this.$route.params.id
diff --git a/src/renderer/views/Settings/Settings.js b/src/renderer/views/Settings/Settings.js
index 6d1573880..722e37bba 100644
--- a/src/renderer/views/Settings/Settings.js
+++ b/src/renderer/views/Settings/Settings.js
@@ -119,7 +119,7 @@ export default defineComponent({
   },
   computed: {
     locale: function() {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     settingsPassword: function () {
diff --git a/src/renderer/views/SubscribedChannels/SubscribedChannels.js b/src/renderer/views/SubscribedChannels/SubscribedChannels.js
index eda06ec8e..b4410831d 100644
--- a/src/renderer/views/SubscribedChannels/SubscribedChannels.js
+++ b/src/renderer/views/SubscribedChannels/SubscribedChannels.js
@@ -56,7 +56,7 @@ export default defineComponent({
     },
 
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     backendPreference: function () {
diff --git a/src/renderer/views/UserPlaylists/UserPlaylists.js b/src/renderer/views/UserPlaylists/UserPlaylists.js
index a29495f61..053d0b504 100644
--- a/src/renderer/views/UserPlaylists/UserPlaylists.js
+++ b/src/renderer/views/UserPlaylists/UserPlaylists.js
@@ -57,7 +57,7 @@ export default defineComponent({
   },
   computed: {
     locale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
 
     allPlaylists: function () {
diff --git a/src/renderer/views/Watch/Watch.js b/src/renderer/views/Watch/Watch.js
index f5a29b77e..382db3f3a 100644
--- a/src/renderer/views/Watch/Watch.js
+++ b/src/renderer/views/Watch/Watch.js
@@ -201,7 +201,7 @@ export default defineComponent({
       return !this.hideRecommendedVideos || (!this.hideLiveChat && this.isLive) || this.watchingPlaylist
     },
     currentLocale: function () {
-      return this.$i18n.locale.replace('_', '-')
+      return this.$i18n.locale
     },
     hideChapters: function () {
       return this.$store.getters.getHideChapters
diff --git a/static/geolocations/en_GB.json b/static/geolocations/en-GB.json
similarity index 100%
rename from static/geolocations/en_GB.json
rename to static/geolocations/en-GB.json
diff --git a/static/geolocations/es_AR.json b/static/geolocations/es-AR.json
similarity index 100%
rename from static/geolocations/es_AR.json
rename to static/geolocations/es-AR.json
diff --git a/static/geolocations/nb_NO.json b/static/geolocations/nb-NO.json
similarity index 100%
rename from static/geolocations/nb_NO.json
rename to static/geolocations/nb-NO.json
diff --git a/static/locales/activeLocales.json b/static/locales/activeLocales.json
index 58d8b378d..0a0357af8 100644
--- a/static/locales/activeLocales.json
+++ b/static/locales/activeLocales.json
@@ -1,6 +1,6 @@
 [
   "en-US",
-  "en_GB",
+  "en-GB",
   "ar",
   "bg",
   "ca",
@@ -9,7 +9,7 @@
   "de-DE",
   "el",
   "es",
-  "es_AR",
+  "es-AR",
   "es-MX",
   "et",
   "eu",
@@ -26,7 +26,7 @@
   "ja",
   "ko",
   "lt",
-  "nb_NO",
+  "nb-NO",
   "nl",
   "nn",
   "pl",
diff --git a/static/locales/en_GB.yaml b/static/locales/en-GB.yaml
similarity index 100%
rename from static/locales/en_GB.yaml
rename to static/locales/en-GB.yaml
diff --git a/static/locales/es_AR.yaml b/static/locales/es-AR.yaml
similarity index 100%
rename from static/locales/es_AR.yaml
rename to static/locales/es-AR.yaml
diff --git a/static/locales/nb_NO.yaml b/static/locales/nb-NO.yaml
similarity index 100%
rename from static/locales/nb_NO.yaml
rename to static/locales/nb-NO.yaml