diff --git a/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs b/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs
index 915b815033..187b3f0e31 100644
--- a/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs
+++ b/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs
@@ -116,31 +116,13 @@ namespace Umbraco.Cms.Infrastructure.DependencyInjection
         private static LocalizedTextServiceFileSources SourcesFactory(IServiceProvider container)
         {
             var hostingEnvironment = container.GetRequiredService<IHostingEnvironment>();
-            var globalSettings = container.GetRequiredService<IOptions<GlobalSettings>>().Value;
             var mainLangFolder = new DirectoryInfo(hostingEnvironment.MapPathContentRoot(WebPath.Combine(Constants.SystemDirectories.Umbraco, "config", "lang")));
-            var appPlugins = new DirectoryInfo(hostingEnvironment.MapPathContentRoot(Constants.SystemDirectories.AppPlugins));
-            var configLangFolder = new DirectoryInfo(hostingEnvironment.MapPathContentRoot(WebPath.Combine(Constants.SystemDirectories.Config, "lang")));
-
-            var pluginLangFolders = appPlugins.Exists == false
-                ? Enumerable.Empty<LocalizedTextServiceSupplementaryFileSource>()
-                : appPlugins.GetDirectories()
-                    // Check for both Lang & lang to support case sensitive file systems.
-                    .SelectMany(x => x.GetDirectories("?ang", SearchOption.AllDirectories).Where(x => x.Name.InvariantEquals("lang")))
-                    .SelectMany(x => x.GetFiles("*.xml", SearchOption.TopDirectoryOnly))
-                    .Select(x => new LocalizedTextServiceSupplementaryFileSource(x, false));
-
-            // user defined langs that overwrite the default, these should not be used by plugin creators
-            var userLangFolders = configLangFolder.Exists == false
-                ? Enumerable.Empty<LocalizedTextServiceSupplementaryFileSource>()
-                : configLangFolder
-                    .GetFiles("*.user.xml", SearchOption.TopDirectoryOnly)
-                    .Select(x => new LocalizedTextServiceSupplementaryFileSource(x, true));
 
             return new LocalizedTextServiceFileSources(
                 container.GetRequiredService<ILogger<LocalizedTextServiceFileSources>>(),
                 container.GetRequiredService<AppCaches>(),
                 mainLangFolder,
-                pluginLangFolders.Concat(userLangFolders));
+                container.GetServices<LocalizedTextServiceSupplementaryFileSource>());
         }
     }
 }
diff --git a/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilder.LocalizedText.cs b/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilder.LocalizedText.cs
new file mode 100644
index 0000000000..5deccd14f0
--- /dev/null
+++ b/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilder.LocalizedText.cs
@@ -0,0 +1,94 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.FileProviders;
+
+using Umbraco.Cms.Core.DependencyInjection;
+using Umbraco.Cms.Core.Routing;
+using Umbraco.Cms.Core.Services.Implement;
+
+using IHostingEnvironment = Umbraco.Cms.Core.Hosting.IHostingEnvironment;
+
+namespace Umbraco.Extensions
+{
+    /// <summary>
+    /// Extension methods for <see cref="IUmbracoBuilder"/> for the Umbraco back office
+    /// </summary>
+    public static partial class UmbracoBuilderExtensions
+    {
+        /// <summary>
+        ///  Add the SupplementaryLocalizedTextFilesSources 
+        /// </summary>
+        /// <param name="builder"></param>
+        /// <returns></returns>
+        private static IUmbracoBuilder AddSupplemenataryLocalizedTextFileSources(this IUmbracoBuilder builder)
+        {
+            builder.Services.AddTransient(sp =>
+            {
+                return GetSupplementaryFileSources(
+                    sp.GetRequiredService<IHostingEnvironment>(),
+                    sp.GetRequiredService<IWebHostEnvironment>());
+            });
+
+            return builder;
+        }
+
+
+        /// <summary>
+        ///  Loads the suplimentary localization files from plugins and user config
+        /// </summary>
+        private static IEnumerable<LocalizedTextServiceSupplementaryFileSource> GetSupplementaryFileSources(
+            IHostingEnvironment hostingEnvironment,
+            IWebHostEnvironment webHostEnvironment)
+        {
+            var webFileProvider = webHostEnvironment.WebRootFileProvider;
+            var contentFileProvider = webHostEnvironment.ContentRootFileProvider;
+
+            // plugins in /app_plugins
+            var pluginLangFolders = GetPluginLanguageFileSources(contentFileProvider, Cms.Core.Constants.SystemDirectories.AppPlugins, false);
+
+            // files in /wwwroot/app_plugins (or any virtual location that maps to this)
+            var razorPluginFolders = GetPluginLanguageFileSources(webFileProvider, Cms.Core.Constants.SystemDirectories.AppPlugins, false);
+
+            // user defined langs that overwrite the default, these should not be used by plugin creators
+            var configLangFolder = new DirectoryInfo(hostingEnvironment.MapPathContentRoot(WebPath.Combine(Cms.Core.Constants.SystemDirectories.Config, "lang")));
+
+            var userLangFolders = configLangFolder.Exists == false
+                ? Enumerable.Empty<LocalizedTextServiceSupplementaryFileSource>()
+                : configLangFolder
+                    .GetFiles("*.user.xml", SearchOption.TopDirectoryOnly)
+                    .Select(x => new LocalizedTextServiceSupplementaryFileSource(x, true));
+
+            // returned in order where userLangFolders takes precedence over plugins
+            return pluginLangFolders
+                .Concat(razorPluginFolders)
+                .Concat(userLangFolders);
+        }
+
+
+        /// <summary>
+        ///  Loads the suplimentary localaization files via the file provider.
+        /// </summary>
+        /// <remarks>
+        ///  locates all *.xml files in the lang folder of any sub folder of the one provided.
+        ///  e.g /app_plugins/plugin-name/lang/*.xml
+        /// </remarks>
+        private static IEnumerable<LocalizedTextServiceSupplementaryFileSource> GetPluginLanguageFileSources(
+            IFileProvider fileProvider, string folder, bool overwriteCoreKeys)
+        {
+            // locate all the *.xml files inside Lang folders inside folders of the main folder
+            // e.g. /app_plugins/plugin-name/lang/*.xml
+
+            return fileProvider.GetDirectoryContents(folder)
+                .Where(x => x.IsDirectory)
+                .SelectMany(x => fileProvider.GetDirectoryContents(WebPath.Combine(folder, x.Name)))
+                .Where(x => x.IsDirectory && x.Name.InvariantEquals("lang"))
+                .Select(x => new DirectoryInfo(x.PhysicalPath))
+                .SelectMany(x => x.GetFiles("*.xml", SearchOption.TopDirectoryOnly))
+                .Select(x => new LocalizedTextServiceSupplementaryFileSource(x, overwriteCoreKeys));
+        }
+    }
+}
diff --git a/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilderExtensions.cs b/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilderExtensions.cs
index 63027a3c9e..df09e9a9b2 100644
--- a/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilderExtensions.cs
+++ b/src/Umbraco.Web.BackOffice/DependencyInjection/UmbracoBuilderExtensions.cs
@@ -56,7 +56,8 @@ namespace Umbraco.Extensions
                 .AddLogViewer()
                 .AddExamine()
                 .AddExamineIndexes()
-                .AddControllersWithAmbiguousConstructors();
+                .AddControllersWithAmbiguousConstructors()
+                .AddSupplemenataryLocalizedTextFileSources();
 
         public static IUmbracoBuilder AddUnattendedInstallInstallCreateUser(this IUmbracoBuilder builder)
         {