diff --git a/Modules/GenHTTP.Modules.I18n/Parsers/LanguageParser.cs b/Modules/GenHTTP.Modules.I18n/Parsers/LanguageParser.cs
index ba6fcc0b..7a620110 100644
--- a/Modules/GenHTTP.Modules.I18n/Parsers/LanguageParser.cs
+++ b/Modules/GenHTTP.Modules.I18n/Parsers/LanguageParser.cs
@@ -44,7 +44,6 @@ public static CultureInfo[] ParseFromLanguage(string? language)
 
         try
         {
-
             var actualCount = 0;
             var start = 0;
             int commaIndex;
@@ -95,7 +94,6 @@ public static CultureInfo[] ParseFromLanguage(string? language)
                         rentedArray[actualCount++] = (languagePart.ToString(), qValue);
                     }
                 }
-
             } while (commaIndex >= 0);
 
             if (actualCount == 0)
diff --git a/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcern.cs b/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcern.cs
index 555d6c24..3bdebb59 100644
--- a/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcern.cs
+++ b/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcern.cs
@@ -11,9 +11,9 @@ public sealed class LocalizationConcern : IConcern
     public IHandler Content { get; }
 
     private readonly CultureInfo _defaultCulture;
-    private readonly CultureSelectorDelegate _cultureSelector;
-    private readonly CultureFilterDelegate _cultureFilter;
-    private readonly CultureSetterDelegate _cultureSetter;
+    private readonly CultureSelectorCombinedAsyncDelegate _cultureSelector;
+    private readonly CultureFilterAsyncDelegate _cultureFilter;
+    private readonly CultureSetterAsyncDelegate _cultureSetter;
 
     #endregion
 
@@ -22,9 +22,9 @@ public sealed class LocalizationConcern : IConcern
     public LocalizationConcern(
         IHandler content,
         CultureInfo defaultCulture,
-        CultureSelectorDelegate cultureSelector,
-        CultureFilterDelegate cultureFilter,
-        CultureSetterDelegate cultureSetter
+        CultureSelectorCombinedAsyncDelegate cultureSelector,
+        CultureFilterAsyncDelegate cultureFilter,
+        CultureSetterAsyncDelegate cultureSetter
         )
     {
         Content = content;
@@ -40,13 +40,23 @@ CultureSetterDelegate cultureSetter
 
     #region Functionality
 
+    private async ValueTask<CultureInfo?> ResolveCultureInfoAsync(IRequest request)
+    {
+        await foreach (var candidate in _cultureSelector(request))
+        {
+            if (await _cultureFilter(request, candidate))
+            {
+                return candidate;
+            }
+        }
+        return null;
+    }
+
     public async ValueTask<IResponse?> HandleAsync(IRequest request)
     {
-        var culture = (_cultureSelector(request) ?? [])
-            .FirstOrDefault(c => _cultureFilter(request, c))
-            ?? _defaultCulture;
+        var culture = await ResolveCultureInfoAsync(request) ?? _defaultCulture;
 
-        _cultureSetter(request, culture);
+        await _cultureSetter(request, culture);
 
         return await Content.HandleAsync(request);
     }
diff --git a/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcernBuilder.cs b/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcernBuilder.cs
index 89bb5d3d..06dd3db0 100644
--- a/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcernBuilder.cs
+++ b/Modules/GenHTTP.Modules.I18n/Provider/LocalizationConcernBuilder.cs
@@ -14,9 +14,9 @@ public sealed class LocalizationConcernBuilder : IConcernBuilder
 
     private CultureInfo _defaultCulture = CultureInfo.CurrentCulture;
 
-    private readonly List<CultureSelectorDelegate> _cultureSelectors = [];
-    private CultureFilterDelegate _cultureFilter = (_, _) => true;
-    private readonly List<CultureSetterDelegate> _cultureSetters = [];
+    private readonly List<CultureSelectorAsyncDelegate> _cultureSelectors = [];
+    private CultureFilterAsyncDelegate _cultureFilter = (_, _) => ValueTask.FromResult(true);
+    private readonly List<CultureSetterAsyncDelegate> _cultureSetters = [];
 
     #endregion
 
@@ -46,13 +46,19 @@ public LocalizationConcernBuilder FromHeader(string headerName = "Accept-Languag
         });
 
     public LocalizationConcernBuilder FromLanguage(Func<IRequest, string?> languageSelector)
-        => FromRequest(request =>
+        => FromLanguage(request => ValueTask.FromResult(languageSelector(request)));
+
+    public LocalizationConcernBuilder FromLanguage(Func<IRequest, ValueTask<string?>> languageSelector)
+        => FromRequest(async request =>
         {
-            var language = languageSelector(request);
+            var language = await languageSelector(request);
             return CultureInfoParser.ParseFromLanguage(language);
         });
 
-    public LocalizationConcernBuilder FromRequest(CultureSelectorDelegate cultureSelector)
+    public LocalizationConcernBuilder FromRequest(CultureSelectorDelegate cultureSelector)        
+        => FromRequest(request => ValueTask.FromResult(cultureSelector(request)));
+
+    public LocalizationConcernBuilder FromRequest(CultureSelectorAsyncDelegate cultureSelector)
     {
         _cultureSelectors.Add(cultureSelector);
         return this;
@@ -71,7 +77,13 @@ public LocalizationConcernBuilder Supports(params CultureInfo[] supportedCulture
     public LocalizationConcernBuilder Supports(Predicate<CultureInfo> culturePredicate)
         => Supports((_, culture) => culturePredicate(culture));
 
+    public LocalizationConcernBuilder Supports(Func<CultureInfo, ValueTask<bool>> culturePredicate)
+        => Supports((_, culture) => culturePredicate(culture));
+
     public LocalizationConcernBuilder Supports(CultureFilterDelegate cultureFilter)
+        => Supports((request, culture) => ValueTask.FromResult(cultureFilter(request, culture)));
+
+    public LocalizationConcernBuilder Supports(CultureFilterAsyncDelegate cultureFilter)
     {
         _cultureFilter = cultureFilter;
         return this;
@@ -100,10 +112,20 @@ public LocalizationConcernBuilder Setter(bool currentCulture = false, bool curre
         return this;
     }
 
+    public LocalizationConcernBuilder Setter(Func<CultureInfo, ValueTask> cultureSetter)
+        => Setter((_, culture) => cultureSetter(culture));
+
     public LocalizationConcernBuilder Setter(Action<CultureInfo> cultureSetter)
         => Setter((_, culture) => cultureSetter(culture));
 
     public LocalizationConcernBuilder Setter(CultureSetterDelegate cultureSetter)
+        => Setter((request, culture) => 
+        {
+            cultureSetter(request, culture);
+            return ValueTask.CompletedTask;
+        });
+
+    public LocalizationConcernBuilder Setter(CultureSetterAsyncDelegate cultureSetter)
     {
         _cultureSetters.Add(cultureSetter);
         return this;
@@ -146,14 +168,24 @@ public IConcern Build(IHandler content)
 
     #region Composite functions
 
-    private IEnumerable<CultureInfo> CultureSelector(IRequest request)
-        => _cultureSelectors.SelectMany(selector => selector(request));
+    private async IAsyncEnumerable<CultureInfo> CultureSelector(IRequest request)
+    {        
+        foreach (var selector in _cultureSelectors)
+        {
+            var cultures = await selector(request);
+            foreach (var culture in cultures)
+            {
+                yield return culture;
+            }
+        }
+    }
+
 
-    private void CultureSetter(IRequest request, CultureInfo cultureInfo)
+    private async ValueTask CultureSetter(IRequest request, CultureInfo cultureInfo)
     {
         foreach (var setter in _cultureSetters)
         {
-            setter(request, cultureInfo);
+            await setter(request, cultureInfo);
         }
     }
 
diff --git a/Modules/GenHTTP.Modules.I18n/Provider/Types.cs b/Modules/GenHTTP.Modules.I18n/Provider/Types.cs
index f2b065c6..24f3229b 100644
--- a/Modules/GenHTTP.Modules.I18n/Provider/Types.cs
+++ b/Modules/GenHTTP.Modules.I18n/Provider/Types.cs
@@ -3,6 +3,35 @@
 
 namespace GenHTTP.Modules.I18n.Provider;
 
+/// <summary>
+/// Delegate to extract the cultures for a given request.
+/// </summary>
+/// <param name="request">The request to extract cultures for.</param>
+/// <returns>An enumerable of CultureInfo objects representing the extracted cultures.</returns>
+public delegate IAsyncEnumerable<CultureInfo> CultureSelectorCombinedAsyncDelegate(IRequest request);
+
+/// <summary>
+/// Delegate to extract the cultures for a given request.
+/// </summary>
+/// <param name="request">The request to extract cultures for.</param>
+/// <returns>An enumerable of CultureInfo objects representing the extracted cultures.</returns>
+public delegate ValueTask<IEnumerable<CultureInfo>> CultureSelectorAsyncDelegate(IRequest request);
+
+/// <summary>
+/// Delegate to set the culture for a given request.
+/// </summary>
+/// <param name="request">The request to set the culture for.</param>
+/// <param name="cultureInfo">The CultureInfo object representing the culture to be set.</param>
+public delegate ValueTask CultureSetterAsyncDelegate(IRequest request, CultureInfo cultureInfo);
+
+/// <summary>
+/// Delegate to filter the cultures for a given request.
+/// </summary>
+/// <param name="request">The request to filter cultures for.</param>
+/// <param name="cultureInfo">The CultureInfo object representing the culture to be filtered.</param>
+/// <returns>True if the culture is valid for the request, otherwise false.</returns>
+public delegate ValueTask<bool> CultureFilterAsyncDelegate(IRequest request, CultureInfo cultureInfo);
+
 /// <summary>
 /// Delegate to extract the cultures for a given request.
 /// </summary>