diff --git a/Libraries/Core/Controllers/InsuranceController.cs b/Libraries/Core/Controllers/InsuranceController.cs
index d0712638..9439f9ac 100644
--- a/Libraries/Core/Controllers/InsuranceController.cs
+++ b/Libraries/Core/Controllers/InsuranceController.cs
@@ -59,11 +59,10 @@ public class InsuranceController(
         }
     }
 
-    /**
-     * Process insurance items of a single profile prior to being given back to the player through the mail service.
-     * 
-     * @returns void
-     */
+    /// <summary>
+    /// Process insurance items of a single profile prior to being given back to the player through the mail service
+    /// </summary>
+    /// <param name="sessionId">Player id</param>
     public void ProcessReturnByProfile(string sessionId)
     {
         // Filter out items that don't need to be processed yet.
@@ -157,13 +156,11 @@ public class InsuranceController(
         return insuranceDetails.Select(ins => ins.Items.Count).Count();
     }
 
-    /**
-     * Remove an insurance package from a profile using the package's system data information.
-     * 
-     * @param sessionID The session ID of the profile to remove the package from.
-     * @param index The array index of the insurance package to remove.
-     * @returns void
-     */
+    /// <summary>
+    /// Remove an insurance package from a profile using the package's system data information.
+    /// </summary>
+    /// <param name="sessionId">The session ID of the profile to remove the package from.</param>
+    /// <param name="insPackage">The array index of the insurance package to remove.</param>
     protected void RemoveInsurancePackageFromProfile(string sessionId, Insurance insPackage)
     {
         var profile = _saveServer.GetProfile(sessionId);
diff --git a/Libraries/Core/Services/CustomLocaleService.cs b/Libraries/Core/Services/CustomLocaleService.cs
index 832fdbb5..2df4f1b4 100644
--- a/Libraries/Core/Services/CustomLocaleService.cs
+++ b/Libraries/Core/Services/CustomLocaleService.cs
@@ -1,26 +1,28 @@
 using Core.Models.Utils;
-using Core.Utils;
 using SptCommon.Annotations;
 
 namespace Core.Services;
 
-[Injectable]
+[Injectable(InjectionType.Singleton)]
 public class CustomLocaleService(
-    ISptLogger<CustomLocaleService> logger,
-    FileUtil fileUtil,
-    DatabaseService databaseService
+    ISptLogger<CustomLocaleService> logger
 )
 {
+    protected Dictionary<string, Dictionary<string, string>> customServerLocales = new();
+    protected Dictionary<string, Dictionary<string, string>> customClientLocales = new();
+
 
     /// <summary>
     /// Path should link to a folder containing every locale that should be added to the server locales
     /// e.g. en.json for english, fr.json for french
     /// Inside each JSON should be a Dictionary of the locale key and localised text
     /// </summary>
-    /// <param name="pathToServerLocales">A path to a folder that contains locales to add to SPT</param>
-    public void AddServerLocales(string pathToServerLocales)
+    /// <param name="locale">en/fr/de</param>
+    /// <param name="localeKey">locale key to store values against</param>
+    /// <param name="localeValue">Localised string to store</param>
+    public void AddServerLocales(string locale, string localeKey, string localeValue)
     {
-
+        AddToDictionary(locale, localeKey, localeValue, customServerLocales);
     }
 
     /// <summary>
@@ -28,9 +30,46 @@ public class CustomLocaleService(
     /// e.g. en.json for english, fr.json for french
     /// Inside each JSON should be a Dictionary of the locale key and localised text
     /// </summary>
-    /// <param name="pathToGameLocales">A path to a folder that contains locales to add to SPT</param>
-    public void AddGameLocales(string pathToGameLocales)
+    /// <param name="locale">en/fr/de</param>
+    /// <param name="localeKey">locale key to store values against</param>
+    /// <param name="localeValue">Localised string to store</param>
+    public void AddGameLocales(string locale, string localeKey, string localeValue)
     {
+        AddToDictionary(locale, localeKey, localeValue, customClientLocales);
+    }
 
+    protected void AddToDictionary(string locale, string localeKey, string localeValue,
+        Dictionary<string, Dictionary<string, string>> dictionaryToAddTo)
+    {
+        dictionaryToAddTo.TryAdd(locale, new Dictionary<string, string>());
+        if (!dictionaryToAddTo.TryGetValue(locale, out var localeDictToAddTo))
+        {
+            logger.Error($"Unable to get custom locale dictionary keyed by: {locale}");
+
+            return;
+        }
+
+        if (!localeDictToAddTo.TryAdd(localeKey, localeValue))
+        {
+            logger.Error($"Unable to add: {localeKey} {localeValue} to custom locale dictionary: {locale}");
+        }
+    }
+
+    public string? GetServerValue(string locale, string localeKey)
+    {
+        return GetValueFromDictionary(locale, localeKey, customServerLocales);
+    }
+
+    public string? GetClientValue(string locale, string localeKey)
+    {
+        return GetValueFromDictionary(locale, localeKey, customClientLocales);
+    }
+
+    protected string? GetValueFromDictionary(string locale, string localeKey,
+        Dictionary<string, Dictionary<string, string>> dictionaryToGetFrom)
+    {
+        return dictionaryToGetFrom.TryGetValue(locale, out var localeDictToGetFrom)
+            ? localeDictToGetFrom.GetValueOrDefault(localeKey) // Locale exists, look up value or return null
+            : null; // No locale (e.g. en/fr/de) at all
     }
 }
diff --git a/Libraries/Core/Services/I18nService.cs b/Libraries/Core/Services/I18nService.cs
index aa284964..751f9ded 100644
--- a/Libraries/Core/Services/I18nService.cs
+++ b/Libraries/Core/Services/I18nService.cs
@@ -11,6 +11,7 @@ public class I18nService
     private readonly Dictionary<string, string> _fallbacks;
     private readonly FileUtil _fileUtil;
     private readonly JsonUtil _jsonUtil;
+    private readonly CustomLocaleService _customLocaleService;
 
     private readonly Dictionary<string, LazyLoad<Dictionary<string, string>>> _loadedLocales = new();
     private HashSet<string> _locales;
@@ -19,6 +20,7 @@ public class I18nService
     public I18nService(
         FileUtil fileUtil,
         JsonUtil jsonUtil,
+        CustomLocaleService customLocaleService,
         HashSet<string> locales,
         Dictionary<string, string> fallbacks,
         string defaultLocale,
@@ -30,6 +32,7 @@ public class I18nService
         _defaultLocale = defaultLocale;
         _directory = directory;
         _jsonUtil = jsonUtil;
+        _customLocaleService = customLocaleService;
         _fileUtil = fileUtil;
 
         Initialize();
@@ -96,7 +99,11 @@ public class I18nService
         if (!locales.Value.TryGetValue(key, out var value))
         {
             _loadedLocales.TryGetValue(_defaultLocale, out var defaults);
-            defaults.Value.TryGetValue(key, out value);
+            if (!defaults.Value.TryGetValue(key, out value))
+            {
+                value = _customLocaleService.GetClientValue(_defaultLocale, key);
+            }
+
             return value ?? key;
         }
 
diff --git a/Libraries/Core/Services/LocalisationService.cs b/Libraries/Core/Services/LocalisationService.cs
index 811e8b29..4003b617 100644
--- a/Libraries/Core/Services/LocalisationService.cs
+++ b/Libraries/Core/Services/LocalisationService.cs
@@ -19,6 +19,7 @@ public class LocalisationService
     public LocalisationService(
         ISptLogger<LocalisationService> logger,
         RandomUtil randomUtil,
+        CustomLocaleService customLocaleService,
         DatabaseServer databaseServer,
         LocaleService localeService,
         JsonUtil jsonUtil,
@@ -32,6 +33,7 @@ public class LocalisationService
         _i18nService = new I18nService(
             fileUtil,
             jsonUtil,
+            customLocaleService,
             localeService.GetServerSupportedLocales().ToHashSet(),
             localeService.GetLocaleFallbacks(),
             "en",