diff --git a/app/assets/js/authmanager.js b/app/assets/js/authmanager.js
index 3f431440..5a24f30a 100644
--- a/app/assets/js/authmanager.js
+++ b/app/assets/js/authmanager.js
@@ -12,12 +12,122 @@
 const ConfigManager          = require('./configmanager')
 const { LoggerUtil }         = require('helios-core')
 const { RestResponseStatus } = require('helios-core/common')
-const { MojangRestAPI, mojangErrorDisplayable, MojangErrorCode } = require('helios-core/mojang')
-const { MicrosoftAuth, microsoftErrorDisplayable, MicrosoftErrorCode } = require('helios-core/microsoft')
+const { MojangRestAPI, MojangErrorCode } = require('helios-core/mojang')
+const { MicrosoftAuth, MicrosoftErrorCode } = require('helios-core/microsoft')
 const { AZURE_CLIENT_ID }    = require('./ipcconstants')
+const Lang = require('./langloader')
 
 const log = LoggerUtil.getLogger('AuthManager')
 
+// Error messages
+
+function microsoftErrorDisplayable(errorCode) {
+    switch (errorCode) {
+        case MicrosoftErrorCode.NO_PROFILE:
+            return {
+                title: Lang.queryJS('auth.microsoft.error.noProfileTitle'),
+                desc: Lang.queryJS('auth.microsoft.error.noProfileDesc')
+            }
+        case MicrosoftErrorCode.NO_XBOX_ACCOUNT:
+            return {
+                title: Lang.queryJS('auth.microsoft.error.noXboxAccountTitle'),
+                desc: Lang.queryJS('auth.microsoft.error.noXboxAccountDesc')
+            }
+        case MicrosoftErrorCode.XBL_BANNED:
+            return {
+                title: Lang.queryJS('auth.microsoft.error.xblBannedTitle'),
+                desc: Lang.queryJS('auth.microsoft.error.xblBannedDesc')
+            }
+        case MicrosoftErrorCode.UNDER_18:
+            return {
+                title: Lang.queryJS('auth.microsoft.error.under18Title'),
+                desc: Lang.queryJS('auth.microsoft.error.under18Desc')
+            }
+        case MicrosoftErrorCode.UNKNOWN:
+            return {
+                title: Lang.queryJS('auth.microsoft.error.unknownTitle'),
+                desc: Lang.queryJS('auth.microsoft.error.unknownDesc')
+            }
+    }
+}
+
+function mojangErrorDisplayable(errorCode) {
+    switch(errorCode) {
+        case MojangErrorCode.ERROR_METHOD_NOT_ALLOWED:
+            return {
+                title: Lang.queryJS('auth.mojang.error.methodNotAllowedTitle'),
+                desc: Lang.queryJS('auth.mojang.error.methodNotAllowedDesc')
+            }
+        case MojangErrorCode.ERROR_NOT_FOUND:
+            return {
+                title: Lang.queryJS('auth.mojang.error.notFoundTitle'),
+                desc: Lang.queryJS('auth.mojang.error.notFoundDesc')
+            }
+        case MojangErrorCode.ERROR_USER_MIGRATED:
+            return {
+                title: Lang.queryJS('auth.mojang.error.accountMigratedTitle'),
+                desc: Lang.queryJS('auth.mojang.error.accountMigratedDesc')
+            }
+        case MojangErrorCode.ERROR_INVALID_CREDENTIALS:
+            return {
+                title: Lang.queryJS('auth.mojang.error.invalidCredentialsTitle'),
+                desc: Lang.queryJS('auth.mojang.error.invalidCredentialsDesc')
+            }
+        case MojangErrorCode.ERROR_RATELIMIT:
+            return {
+                title: Lang.queryJS('auth.mojang.error.tooManyAttemptsTitle'),
+                desc: Lang.queryJS('auth.mojang.error.tooManyAttemptsDesc')
+            }
+        case MojangErrorCode.ERROR_INVALID_TOKEN:
+            return {
+                title: Lang.queryJS('auth.mojang.error.invalidTokenTitle'),
+                desc: Lang.queryJS('auth.mojang.error.invalidTokenDesc')
+            }
+        case MojangErrorCode.ERROR_ACCESS_TOKEN_HAS_PROFILE:
+            return {
+                title: Lang.queryJS('auth.mojang.error.tokenHasProfileTitle'),
+                desc: Lang.queryJS('auth.mojang.error.tokenHasProfileDesc')
+            }
+        case MojangErrorCode.ERROR_CREDENTIALS_MISSING:
+            return {
+                title: Lang.queryJS('auth.mojang.error.credentialsMissingTitle'),
+                desc: Lang.queryJS('auth.mojang.error.credentialsMissingDesc')
+            }
+        case MojangErrorCode.ERROR_INVALID_SALT_VERSION:
+            return {
+                title: Lang.queryJS('auth.mojang.error.invalidSaltVersionTitle'),
+                desc: Lang.queryJS('auth.mojang.error.invalidSaltVersionDesc')
+            }
+        case MojangErrorCode.ERROR_UNSUPPORTED_MEDIA_TYPE:
+            return {
+                title: Lang.queryJS('auth.mojang.error.unsupportedMediaTypeTitle'),
+                desc: Lang.queryJS('auth.mojang.error.unsupportedMediaTypeDesc')
+            }
+        case MojangErrorCode.ERROR_GONE:
+            return {
+                title: Lang.queryJS('auth.mojang.error.accountGoneTitle'),
+                desc: Lang.queryJS('auth.mojang.error.accountGoneDesc')
+            }
+        case MojangErrorCode.ERROR_UNREACHABLE:
+            return {
+                title: Lang.queryJS('auth.mojang.error.unreachableTitle'),
+                desc: Lang.queryJS('auth.mojang.error.unreachableDesc')
+            }
+        case MojangErrorCode.ERROR_NOT_PAID:
+            return {
+                title: Lang.queryJS('auth.mojang.error.gameNotPurchasedTitle'),
+                desc: Lang.queryJS('auth.mojang.error.gameNotPurchasedDesc')
+            }
+        case MojangErrorCode.UNKNOWN:
+            return {
+                title: Lang.queryJS('auth.mojang.error.unknownErrorTitle'),
+                desc: Lang.queryJS('auth.mojang.error.unknownErrorDesc')
+            }
+        default:
+            throw new Error(`Unknown error code: ${errorCode}`)
+    }
+}
+
 // Functions
 
 /**
diff --git a/app/assets/lang/en_US.toml b/app/assets/lang/en_US.toml
index 59877b74..758e6379 100644
--- a/app/assets/lang/en_US.toml
+++ b/app/assets/lang/en_US.toml
@@ -295,3 +295,45 @@ selectAnotherAccountButton = "Select Another Account"
 checkingForUpdateButton = "Checking for Updates..."
 installNowButton = "Install Now"
 checkForUpdatesButton = "Check for Updates"
+
+[js.auth.microsoft.error]
+noProfileTitle = "Error During Login:<br>Profile Not Set Up"
+noProfileDesc = "Your Microsoft account does not yet have a Minecraft profile set up. If you have recently purchased the game or redeemed it through Xbox Game Pass, you have to set up your profile on <a href=\"https://minecraft.net/\">Minecraft.net</a>.<br><br>If you have not yet purchased the game, you can also do that on <a href=\"https://minecraft.net/\">Minecraft.net</a>."
+noXboxAccountTitle = "Error During Login:<br>No Xbox Account"
+noXboxAccountDesc = "Your Microsoft account has no Xbox account associated with it."
+xblBannedTitle = "Error During Login:<br>Xbox Live Unavailable"
+xblBannedDesc = "Your Microsoft account is from a country where Xbox Live is not available or banned."
+under18Title = "Error During Login:<br>Parental Approval Required"
+under18Desc = "Accounts for users under the age of 18 must be added to a Family by an adult."
+unknownTitle = "Unknown Error During Login"
+unknownDesc = "An unknown error has occurred. Please see the console for details."
+
+[js.auth.mojang.error]
+methodNotAllowedTitle = "Internal Error:<br>Method Not Allowed"
+methodNotAllowedDesc = "Method not allowed. Please report this error."
+notFoundTitle = "Internal Error:<br>Not Found"
+notFoundDesc = "The authentication endpoint was not found. Please report this issue."
+accountMigratedTitle = "Error During Login:<br>Account Migrated"
+accountMigratedDesc = "You've attempted to login with a migrated account. Try again using the account email as the username."
+invalidCredentialsTitle = "Error During Login:<br>Invalid Credentials"
+invalidCredentialsDesc = "The email or password you've entered is incorrect. Please try again."
+tooManyAttemptsTitle = "Error During Login:<br>Too Many Attempts"
+tooManyAttemptsDesc = "There have been too many login attempts with this account recently. Please try again later."
+invalidTokenTitle = "Error During Login:<br>Invalid Token"
+invalidTokenDesc = "The provided access token is invalid."
+tokenHasProfileTitle = "Error During Login:<br>Token Has Profile"
+tokenHasProfileDesc = "Access token already has a profile assigned. Selecting profiles is not implemented yet."
+credentialsMissingTitle = "Error During Login:<br>Credentials Missing"
+credentialsMissingDesc = "Username/password was not submitted or password is less than 3 characters."
+invalidSaltVersionTitle = "Error During Login:<br>Invalid Salt Version"
+invalidSaltVersionDesc = "Invalid salt version."
+unsupportedMediaTypeTitle = "Internal Error:<br>Unsupported Media Type"
+unsupportedMediaTypeDesc = "Unsupported media type. Please report this error."
+accountGoneTitle = "Error During Login:<br>Account Migrated"
+accountGoneDesc = "Account has been migrated to a Microsoft account. Please log in with Microsoft."
+unreachableTitle = "Error During Login:<br>Unreachable"
+unreachableDesc = "Unable to reach the authentication servers. Ensure that they are online and you are connected to the internet."
+gameNotPurchasedTitle = "Error During Login:<br>Game Not Purchased"
+gameNotPurchasedDesc = "The account you are trying to login with has not purchased a copy of Minecraft. You may purchase a copy on <a href=\"https://minecraft.net/\">Minecraft.net</a>"
+unknownErrorTitle = "Unknown Error During Login"
+unknownErrorDesc = "An unknown error has occurred. Please see the console for details."