diff --git a/src/Altinn.App.Api/Controllers/ResourceController.cs b/src/Altinn.App.Api/Controllers/ResourceController.cs
index e38ad0cc8e..c7e0d18320 100644
--- a/src/Altinn.App.Api/Controllers/ResourceController.cs
+++ b/src/Altinn.App.Api/Controllers/ResourceController.cs
@@ -1,3 +1,4 @@
+using Altinn.App.Core.Features;
 using Altinn.App.Core.Helpers;
 using Altinn.App.Core.Internal.App;
 using Microsoft.AspNetCore.Mvc;
@@ -11,14 +12,17 @@ namespace Altinn.App.Api.Controllers;
 public class ResourceController : ControllerBase
 {
     private readonly IAppResources _appResourceService;
+    private readonly AppImplementationFactory _appImplementationFactory;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="ResourceController"/> class
     /// </summary>
     /// <param name="appResourcesService">The execution service</param>
-    public ResourceController(IAppResources appResourcesService)
+    /// <param name="serviceProvider">The service provider</param>
+    public ResourceController(IAppResources appResourcesService, IServiceProvider serviceProvider)
     {
         _appResourceService = appResourcesService;
+        _appImplementationFactory = serviceProvider.GetRequiredService<AppImplementationFactory>();
     }
 
     /// <summary>
@@ -71,6 +75,44 @@ public ActionResult GetLayouts(string org, string app, string id)
         return Ok(layouts);
     }
 
+    /// <summary>
+    /// Endpoint for layouts with instance context.
+    /// Uses ICustomLayoutForInstance if implemented with IAppResources as fallback.
+    /// </summary>
+    /// <param name="org">The application owner short name</param>
+    /// <param name="app">The application name</param>
+    /// <param name="instanceOwnerPartyId">The instance owner party id</param>
+    /// <param name="instanceId">The instance id</param>
+    /// <param name="layoutSetId">The layout set id</param>
+    /// <returns>A collection of FormLayout objects in JSON format.</returns>
+    [ProducesResponseType(typeof(string), StatusCodes.Status200OK, "application/json")]
+    [HttpGet]
+    [Route("{org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layouts/{layoutSetId}")]
+    public async Task<ActionResult> GetInstanceLayouts(
+        string org,
+        string app,
+        int instanceOwnerPartyId,
+        string instanceId,
+        string layoutSetId
+    )
+    {
+        ICustomLayoutForInstance? customLayoutService = _appImplementationFactory.Get<ICustomLayoutForInstance>();
+        if (customLayoutService is not null)
+        {
+            string? customLayout = await customLayoutService.GetCustomLayoutForInstance(
+                layoutSetId,
+                instanceOwnerPartyId,
+                Guid.Parse(instanceId)
+            );
+            if (customLayout is not null)
+            {
+                return Ok(customLayout);
+            }
+        }
+        string layouts = _appResourceService.GetLayoutsForSet(layoutSetId);
+        return Ok(layouts);
+    }
+
     /// <summary>
     /// Get the layout settings.
     /// </summary>
@@ -86,6 +128,44 @@ public ActionResult GetLayoutSettings(string org, string app)
         return Ok(settings);
     }
 
+    /// <summary>
+    /// Endpoint for layout settings with instance context.
+    /// Uses ICustomLayoutForInstance if implemented with IAppResources as fallback.
+    /// </summary>
+    /// <param name="org">The application owner short name</param>
+    /// <param name="app">The application name</param>
+    /// <param name="instanceOwnerPartyId">The instance owner party id</param>
+    /// <param name="instanceId">The instance id</param>
+    /// <param name="layoutSetId">The layout set id</param>
+    /// <returns>The settings in the form of a string.</returns>
+    [ProducesResponseType(typeof(string), StatusCodes.Status200OK, "application/json")]
+    [HttpGet]
+    [Route("{org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layoutsettings/{layoutSetId}")]
+    public async Task<ActionResult> GetInstanceLayoutSettings(
+        string org,
+        string app,
+        int instanceOwnerPartyId,
+        string instanceId,
+        string layoutSetId
+    )
+    {
+        ICustomLayoutForInstance? customLayoutService = _appImplementationFactory.Get<ICustomLayoutForInstance>();
+        if (customLayoutService is not null)
+        {
+            string? customLayoutSettings = await customLayoutService.GetCustomLayoutSettingsForInstance(
+                layoutSetId,
+                instanceOwnerPartyId,
+                Guid.Parse(instanceId)
+            );
+            if (customLayoutSettings is not null)
+            {
+                return Ok(customLayoutSettings);
+            }
+        }
+        string? settings = _appResourceService.GetLayoutSettingsStringForSet(layoutSetId);
+        return Ok(settings);
+    }
+
     /// <summary>
     /// Get the layout settings.
     /// </summary>
diff --git a/src/Altinn.App.Core/Features/FeatureFlags.cs b/src/Altinn.App.Core/Features/FeatureFlags.cs
index 402dbc4509..a5373e2ff2 100644
--- a/src/Altinn.App.Core/Features/FeatureFlags.cs
+++ b/src/Altinn.App.Core/Features/FeatureFlags.cs
@@ -12,4 +12,11 @@ public static class FeatureFlags
     /// return validation errors in the response body instead of a string.
     /// </summary>
     public const string JsonObjectInDataResponse = "JsonObjectInDataResponse";
+
+    // TODO: write a better summary here
+    /// <summary>
+    /// Enabling this feature changes backend endpoint used for layouts to
+    /// add instance identifier.
+    /// </summary>
+    public const string AddInstanceIdentifierToLayoutRequests = "AddInstanceIdentifierToLayoutRequests";
 }
diff --git a/src/Altinn.App.Core/Internal/App/FrontendFeatures.cs b/src/Altinn.App.Core/Internal/App/FrontendFeatures.cs
index 45c975a29f..e19f9037a3 100644
--- a/src/Altinn.App.Core/Internal/App/FrontendFeatures.cs
+++ b/src/Altinn.App.Core/Internal/App/FrontendFeatures.cs
@@ -26,6 +26,15 @@ public FrontendFeatures(IFeatureManager featureManager)
         {
             _features.Add("jsonObjectInDataResponse", false);
         }
+
+        if (featureManager.IsEnabledAsync(FeatureFlags.AddInstanceIdentifierToLayoutRequests).Result)
+        {
+            _features.Add("addInstanceIdentifierToLayoutRequests", true);
+        }
+        else
+        {
+            _features.Add("addInstanceIdentifierToLayoutRequests", false);
+        }
     }
 
     /// <inheritdoc />
diff --git a/src/Altinn.App.Core/Internal/App/ICustomLayoutForInstance.cs b/src/Altinn.App.Core/Internal/App/ICustomLayoutForInstance.cs
new file mode 100644
index 0000000000..0c1745b098
--- /dev/null
+++ b/src/Altinn.App.Core/Internal/App/ICustomLayoutForInstance.cs
@@ -0,0 +1,26 @@
+using Altinn.App.Core.Features;
+
+namespace Altinn.App.Core.Internal.App;
+
+/// <summary>
+/// Interface for getting custom layouts for an instance.
+/// </summary>
+[ImplementableByApps]
+public interface ICustomLayoutForInstance
+{
+    /// <summary>
+    /// Gets the custom layout
+    /// </summary>
+    /// <param name="layoutSetId">The layout set ID</param>
+    /// <param name="instanceOwnerPartyId">The instance owner party ID</param>
+    /// <param name="instanceGuid">The instance GUID</param>
+    Task<string?> GetCustomLayoutForInstance(string layoutSetId, int instanceOwnerPartyId, Guid instanceGuid);
+
+    /// <summary>
+    /// Gets the custom layout settings
+    /// </summary>
+    /// <param name="layoutSetId">The layout set ID</param>
+    /// <param name="instanceOwnerPartyId">The instance owner party ID</param>
+    /// <param name="instanceGuid">The instance GUID</param>
+    Task<string?> GetCustomLayoutSettingsForInstance(string layoutSetId, int instanceOwnerPartyId, Guid instanceGuid);
+}
diff --git a/src/Altinn.App.Core/Models/DataElementIdentifier.cs b/src/Altinn.App.Core/Models/DataElementIdentifier.cs
index ca5a655ea4..194a7efbd5 100644
--- a/src/Altinn.App.Core/Models/DataElementIdentifier.cs
+++ b/src/Altinn.App.Core/Models/DataElementIdentifier.cs
@@ -55,7 +55,8 @@ public DataElementIdentifier(DataElement dataElement)
     /// <summary>
     /// Implicit conversion to allow DataElements to be used as DataElementIds
     /// </summary>
-    public static implicit operator DataElementIdentifier(DataElement dataElement) => new(dataElement);
+    public static implicit operator DataElementIdentifier(DataElement dataElement) =>
+        dataElement is null ? throw new ArgumentNullException(nameof(dataElement)) : new(dataElement);
 
     /// <summary>
     /// Implicit conversion to allow DataElements to be used as DataElementIds,
diff --git a/test/Altinn.App.Api.Tests/Controllers/ResourceController_CustomLayoutTests.cs b/test/Altinn.App.Api.Tests/Controllers/ResourceController_CustomLayoutTests.cs
new file mode 100644
index 0000000000..a0c6fc37f7
--- /dev/null
+++ b/test/Altinn.App.Api.Tests/Controllers/ResourceController_CustomLayoutTests.cs
@@ -0,0 +1,131 @@
+using System.Net;
+using System.Text.Json;
+using Altinn.App.Api.Tests.Data;
+using Altinn.App.Core.Internal.App;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit.Abstractions;
+
+namespace Altinn.App.Api.Tests.Controllers;
+
+public class ResourceController_CustomLayoutTests : ApiTestBase, IClassFixture<WebApplicationFactory<Program>>
+{
+    public ResourceController_CustomLayoutTests(WebApplicationFactory<Program> factory, ITestOutputHelper outputHelper)
+        : base(factory, outputHelper) { }
+
+    private class CustomLayoutForInstance : ICustomLayoutForInstance
+    {
+        public Task<string?> GetCustomLayoutForInstance(string layoutSetId, int instanceOwnerPartyId, Guid instanceId)
+        {
+            return Task.FromResult<string?>(instanceId.ToString());
+        }
+
+        public Task<string?> GetCustomLayoutSettingsForInstance(
+            string layoutSetId,
+            int instanceOwnerPartyId,
+            Guid instanceId
+        )
+        {
+            return Task.FromResult<string?>(instanceId.ToString());
+        }
+    }
+
+    [Fact]
+    public async Task GetLayoutsForSet_WithCustomLayoutForInstanceService_ReturnsOk()
+    {
+        OverrideServicesForThisTest = (services) =>
+        {
+            services.AddSingleton<ICustomLayoutForInstance, CustomLayoutForInstance>();
+        };
+
+        string org = "tdd";
+        string app = "contributer-restriction";
+        int instanceOwnerPartyId = 500600;
+        Guid instanceGuid = Guid.Parse("cff1cb24-5bc1-4888-8e06-c634753c5144");
+        string layoutSetId = "default";
+        using HttpClient client = GetRootedUserClient(org, app, 1337, instanceOwnerPartyId);
+
+        TestData.PrepareInstance(org, app, instanceOwnerPartyId, instanceGuid);
+        var response = await client.GetAsync(
+            $"/{org}/{app}/instances/{instanceOwnerPartyId}/{instanceGuid}/layouts/{layoutSetId}"
+        );
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var content = await response.Content.ReadAsStringAsync();
+        Assert.Equal(instanceGuid.ToString(), content);
+    }
+
+    [Fact]
+    public async Task GetLayoutsForSet_WithoutCustomLayoutForInstanceService_ReturnsOk()
+    {
+        string org = "tdd";
+        string app = "contributer-restriction";
+        int instanceOwnerPartyId = 500600;
+        Guid instanceGuid = Guid.Parse("cff1cb24-5bc1-4888-8e06-c634753c5144");
+        string layoutSetId = "default";
+        using HttpClient client = GetRootedUserClient(org, app, 1337, instanceOwnerPartyId);
+
+        TestData.PrepareInstance(org, app, instanceOwnerPartyId, instanceGuid);
+        var response = await client.GetAsync(
+            $"/{org}/{app}/instances/{instanceOwnerPartyId}/{instanceGuid}/layouts/{layoutSetId}"
+        );
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var content = await response.Content.ReadAsStringAsync();
+        using var jsonDoc = JsonDocument.Parse(content);
+        var root = jsonDoc.RootElement;
+        Assert.Equal(JsonValueKind.Object, root.ValueKind);
+        Assert.True(root.TryGetProperty("page", out var pageLayout));
+        Assert.True(pageLayout.TryGetProperty("data", out var data));
+        Assert.True(data.TryGetProperty("layout", out var layout));
+        Assert.Equal(JsonValueKind.Array, layout.ValueKind);
+        Assert.True(layout.GetArrayLength() > 0);
+    }
+
+    [Fact]
+    public async Task GetLayoutSettingsForSet_WithCustomLayoutForInstanceService_ReturnsOk()
+    {
+        OverrideServicesForThisTest = (services) =>
+        {
+            services.AddSingleton<ICustomLayoutForInstance, CustomLayoutForInstance>();
+        };
+
+        string org = "tdd";
+        string app = "contributer-restriction";
+        int instanceOwnerPartyId = 500600;
+        Guid instanceGuid = Guid.Parse("cff1cb24-5bc1-4888-8e06-c634753c5144");
+        string layoutSetId = "default";
+        using HttpClient client = GetRootedUserClient(org, app, 1337, instanceOwnerPartyId);
+
+        TestData.PrepareInstance(org, app, instanceOwnerPartyId, instanceGuid);
+        var response = await client.GetAsync(
+            $"/{org}/{app}/instances/{instanceOwnerPartyId}/{instanceGuid}/layoutsettings/{layoutSetId}"
+        );
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var content = await response.Content.ReadAsStringAsync();
+        Assert.Equal(instanceGuid.ToString(), content);
+    }
+
+    [Fact]
+    public async Task GetLayoutSettingsForSet_WithoutCustomLayoutForInstanceService_ReturnsOk()
+    {
+        string org = "tdd";
+        string app = "contributer-restriction";
+        int instanceOwnerPartyId = 500600;
+        Guid instanceGuid = Guid.Parse("cff1cb24-5bc1-4888-8e06-c634753c5144");
+        string layoutSetId = "default";
+        using HttpClient client = GetRootedUserClient(org, app, 1337, instanceOwnerPartyId);
+
+        TestData.PrepareInstance(org, app, instanceOwnerPartyId, instanceGuid);
+        var response = await client.GetAsync(
+            $"/{org}/{app}/instances/{instanceOwnerPartyId}/{instanceGuid}/layoutsettings/{layoutSetId}"
+        );
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var content = await response.Content.ReadAsStringAsync();
+        using var jsonDoc = JsonDocument.Parse(content);
+        var root = jsonDoc.RootElement;
+        Assert.Equal(JsonValueKind.Object, root.ValueKind);
+    }
+}
diff --git a/test/Altinn.App.Api.Tests/OpenApi/OpenApiSpecChangeDetection.SaveJsonSwagger.verified.json b/test/Altinn.App.Api.Tests/OpenApi/OpenApiSpecChangeDetection.SaveJsonSwagger.verified.json
index 488438728d..97f4fcbe7c 100644
--- a/test/Altinn.App.Api.Tests/OpenApi/OpenApiSpecChangeDetection.SaveJsonSwagger.verified.json
+++ b/test/Altinn.App.Api.Tests/OpenApi/OpenApiSpecChangeDetection.SaveJsonSwagger.verified.json
@@ -5440,6 +5440,74 @@
         }
       }
     },
+    "/{org}/{app}/instances/{instanceOwnerPartyId}/{instanceId}/layouts/{layoutSetId}": {
+      "get": {
+        "tags": [
+          "Resource"
+        ],
+        "summary": "Endpoint for layouts with instance context.\nUses ICustomLayoutForInstance if implemented with IAppResources as fallback.",
+        "parameters": [
+          {
+            "name": "org",
+            "in": "path",
+            "description": "The application owner short name",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "app",
+            "in": "path",
+            "description": "The application name",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "instanceOwnerPartyId",
+            "in": "path",
+            "description": "The instance owner party id",
+            "required": true,
+            "schema": {
+              "type": "integer",
+              "format": "int32"
+            }
+          },
+          {
+            "name": "instanceId",
+            "in": "path",
+            "description": "The instance id",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "layoutSetId",
+            "in": "path",
+            "description": "The layout set id",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "string"
+                }
+              }
+            }
+          }
+        }
+      }
+    },
     "/{org}/{app}/api/layoutsettings": {
       "get": {
         "tags": [
@@ -5480,6 +5548,74 @@
         }
       }
     },
+    "/{org}/{app}/instances/{instanceOwnerPartyId}/{instanceId}/layoutsettings/{layoutSetId}": {
+      "get": {
+        "tags": [
+          "Resource"
+        ],
+        "summary": "Endpoint for layout settings with instance context.\nUses ICustomLayoutForInstance if implemented with IAppResources as fallback.",
+        "parameters": [
+          {
+            "name": "org",
+            "in": "path",
+            "description": "The application owner short name",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "app",
+            "in": "path",
+            "description": "The application name",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "instanceOwnerPartyId",
+            "in": "path",
+            "description": "The instance owner party id",
+            "required": true,
+            "schema": {
+              "type": "integer",
+              "format": "int32"
+            }
+          },
+          {
+            "name": "instanceId",
+            "in": "path",
+            "description": "The instance id",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          },
+          {
+            "name": "layoutSetId",
+            "in": "path",
+            "description": "The layout set id",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "string"
+                }
+              }
+            }
+          }
+        }
+      }
+    },
     "/{org}/{app}/api/layoutsettings/{id}": {
       "get": {
         "tags": [
diff --git a/test/Altinn.App.Api.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt b/test/Altinn.App.Api.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt
index fb9c76b447..9b0af95cea 100644
--- a/test/Altinn.App.Api.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt
+++ b/test/Altinn.App.Api.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt
@@ -523,7 +523,7 @@ namespace Altinn.App.Api.Controllers
     [Microsoft.AspNetCore.Mvc.ApiController]
     public class ResourceController : Microsoft.AspNetCore.Mvc.ControllerBase
     {
-        public ResourceController(Altinn.App.Core.Internal.App.IAppResources appResourcesService) { }
+        public ResourceController(Altinn.App.Core.Internal.App.IAppResources appResourcesService, System.IServiceProvider serviceProvider) { }
         [Microsoft.AspNetCore.Mvc.HttpGet]
         [Microsoft.AspNetCore.Mvc.ProducesResponseType(204)]
         [Microsoft.AspNetCore.Mvc.ProducesResponseType(typeof(string), 200, "application/json", new string[0])]
@@ -531,6 +531,16 @@ namespace Altinn.App.Api.Controllers
         public System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.ActionResult> GetFooterLayout(string org, string app) { }
         [Microsoft.AspNetCore.Mvc.HttpGet]
         [Microsoft.AspNetCore.Mvc.ProducesResponseType(typeof(string), 200, "application/json", new string[0])]
+        [Microsoft.AspNetCore.Mvc.Route("{org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layoutsettings/{lay" +
+            "outSetId}")]
+        public System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.ActionResult> GetInstanceLayoutSettings(string org, string app, int instanceOwnerPartyId, string instanceId, string layoutSetId) { }
+        [Microsoft.AspNetCore.Mvc.HttpGet]
+        [Microsoft.AspNetCore.Mvc.ProducesResponseType(typeof(string), 200, "application/json", new string[0])]
+        [Microsoft.AspNetCore.Mvc.Route("{org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layouts/{layoutSetI" +
+            "d}")]
+        public System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.ActionResult> GetInstanceLayouts(string org, string app, int instanceOwnerPartyId, string instanceId, string layoutSetId) { }
+        [Microsoft.AspNetCore.Mvc.HttpGet]
+        [Microsoft.AspNetCore.Mvc.ProducesResponseType(typeof(string), 200, "application/json", new string[0])]
         [Microsoft.AspNetCore.Mvc.Route("{org}/{app}/api/layoutsets")]
         public Microsoft.AspNetCore.Mvc.ActionResult GetLayoutSets(string org, string app) { }
         [Microsoft.AspNetCore.Mvc.HttpGet]
diff --git a/test/Altinn.App.Core.Tests/Internal/App/AppMetadataTest.GetApplicationMetadata_deserialize_serialize_unmapped_properties.verified.txt b/test/Altinn.App.Core.Tests/Internal/App/AppMetadataTest.GetApplicationMetadata_deserialize_serialize_unmapped_properties.verified.txt
index e847f790dc..9ebfdf0b25 100644
--- a/test/Altinn.App.Core.Tests/Internal/App/AppMetadataTest.GetApplicationMetadata_deserialize_serialize_unmapped_properties.verified.txt
+++ b/test/Altinn.App.Core.Tests/Internal/App/AppMetadataTest.GetApplicationMetadata_deserialize_serialize_unmapped_properties.verified.txt
@@ -3,7 +3,8 @@
   "Features": {
     "footer": true,
     "processActions": true,
-    "jsonObjectInDataResponse": false
+    "jsonObjectInDataResponse": false,
+    "addInstanceIdentifierToLayoutRequests": false
   },
   "OnEntry": {
     "InstanceSelection": null,
diff --git a/test/Altinn.App.Core.Tests/Internal/App/FrontendFeaturesTest.cs b/test/Altinn.App.Core.Tests/Internal/App/FrontendFeaturesTest.cs
index b5f6f5f747..95c27b0816 100644
--- a/test/Altinn.App.Core.Tests/Internal/App/FrontendFeaturesTest.cs
+++ b/test/Altinn.App.Core.Tests/Internal/App/FrontendFeaturesTest.cs
@@ -17,6 +17,7 @@ public async Task GetFeatures_returns_list_of_enabled_features()
             { "footer", true },
             { "processActions", true },
             { "jsonObjectInDataResponse", false },
+            { "addInstanceIdentifierToLayoutRequests", false },
         };
         var featureManagerMock = new Mock<IFeatureManager>();
         IFrontendFeatures frontendFeatures = new FrontendFeatures(featureManagerMock.Object);
@@ -34,9 +35,13 @@ public async Task GetFeatures_returns_list_of_enabled_features_when_feature_flag
             { "footer", true },
             { "processActions", true },
             { "jsonObjectInDataResponse", true },
+            { "addInstanceIdentifierToLayoutRequests", true },
         };
         var featureManagerMock = new Mock<IFeatureManager>();
         featureManagerMock.Setup(f => f.IsEnabledAsync(FeatureFlags.JsonObjectInDataResponse)).ReturnsAsync(true);
+        featureManagerMock
+            .Setup(f => f.IsEnabledAsync(FeatureFlags.AddInstanceIdentifierToLayoutRequests))
+            .ReturnsAsync(true);
         IFrontendFeatures frontendFeatures = new FrontendFeatures(featureManagerMock.Object);
         var actual = await frontendFeatures.GetFrontendFeatures();
         actual.Should().BeEquivalentTo(expected);
diff --git a/test/Altinn.App.Core.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt b/test/Altinn.App.Core.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt
index ec33a03324..7164f6b0c0 100644
--- a/test/Altinn.App.Core.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt
+++ b/test/Altinn.App.Core.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt
@@ -1150,6 +1150,7 @@ namespace Altinn.App.Core.Features
     }
     public static class FeatureFlags
     {
+        public const string AddInstanceIdentifierToLayoutRequests = "AddInstanceIdentifierToLayoutRequests";
         public const string JsonObjectInDataResponse = "JsonObjectInDataResponse";
     }
     public interface IAppOptionsProvider
@@ -2930,6 +2931,11 @@ namespace Altinn.App.Core.Internal.App
     {
         System.Threading.Tasks.Task<Altinn.Platform.Storage.Interface.Models.Application?> GetApplication(string org, string app);
     }
+    public interface ICustomLayoutForInstance
+    {
+        System.Threading.Tasks.Task<string?> GetCustomLayoutForInstance(string layoutSetId, int instanceOwnerPartyId, System.Guid instanceGuid);
+        System.Threading.Tasks.Task<string?> GetCustomLayoutSettingsForInstance(string layoutSetId, int instanceOwnerPartyId, System.Guid instanceGuid);
+    }
     public interface IFrontendFeatures
     {
         System.Threading.Tasks.Task<System.Collections.Generic.Dictionary<string, bool>> GetFrontendFeatures();
diff --git a/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Custom_0_Metadata.verified.txt b/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Custom_0_Metadata.verified.txt
index 4f24127ecb..f5216f4b51 100644
--- a/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Custom_0_Metadata.verified.txt
+++ b/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Custom_0_Metadata.verified.txt
@@ -715,6 +715,34 @@
           ]
         }
       },
+      {
+        endpoint: GET {org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layouts/{layoutSetId},
+        metadata: {
+          errorMessageTextResourceKeyUser: authorization.scopes.insufficient,
+          errorMessageTextResourceKeyServiceOwner: authorization.scopes.insufficient,
+          requiredScopesUsers: [
+            custom:instances.read,
+            altinn:portal/enduser
+          ],
+          requiredScopesServiceOwners: [
+            custom:serviceowner/instances.read
+          ]
+        }
+      },
+      {
+        endpoint: GET {org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layoutsettings/{layoutSetId},
+        metadata: {
+          errorMessageTextResourceKeyUser: authorization.scopes.insufficient,
+          errorMessageTextResourceKeyServiceOwner: authorization.scopes.insufficient,
+          requiredScopesUsers: [
+            custom:instances.read,
+            altinn:portal/enduser
+          ],
+          requiredScopesServiceOwners: [
+            custom:serviceowner/instances.read
+          ]
+        }
+      },
       {
         endpoint: GET {org}/{app}/legacy/instances/{instanceOwnerPartyId:int}/{instanceGuid:guid}/copy,
         metadata: {
diff --git a/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Standard_0_Metadata.verified.txt b/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Standard_0_Metadata.verified.txt
index 3ae594f897..a6cdcb811a 100644
--- a/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Standard_0_Metadata.verified.txt
+++ b/test/Altinn.App.Integration.Tests/CustomScopes/_snapshots/CustomScopesTests.Metadata_Standard_0_Metadata.verified.txt
@@ -580,6 +580,24 @@
           requiredScopesServiceOwners: null
         }
       },
+      {
+        endpoint: GET {org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layouts/{layoutSetId},
+        metadata: {
+          errorMessageTextResourceKeyUser: null,
+          errorMessageTextResourceKeyServiceOwner: null,
+          requiredScopesUsers: null,
+          requiredScopesServiceOwners: null
+        }
+      },
+      {
+        endpoint: GET {org}/{app}/instances/{instanceOwnerPartyId:int}/{instanceId}/layoutsettings/{layoutSetId},
+        metadata: {
+          errorMessageTextResourceKeyUser: null,
+          errorMessageTextResourceKeyServiceOwner: null,
+          requiredScopesUsers: null,
+          requiredScopesServiceOwners: null
+        }
+      },
       {
         endpoint: GET {org}/{app}/legacy/instances/{instanceOwnerPartyId:int}/{instanceGuid:guid}/copy,
         metadata: {
diff --git a/test/Altinn.App.Integration.Tests/PartyTypesAllowed/_snapshots/SubunitOnlyAppTests.ApplicationMetadata_0.verified.txt b/test/Altinn.App.Integration.Tests/PartyTypesAllowed/_snapshots/SubunitOnlyAppTests.ApplicationMetadata_0.verified.txt
index 490482384b..abf291d5c2 100644
--- a/test/Altinn.App.Integration.Tests/PartyTypesAllowed/_snapshots/SubunitOnlyAppTests.ApplicationMetadata_0.verified.txt
+++ b/test/Altinn.App.Integration.Tests/PartyTypesAllowed/_snapshots/SubunitOnlyAppTests.ApplicationMetadata_0.verified.txt
@@ -55,6 +55,7 @@
   Response: {
     Id: ttd/basic,
     Features: {
+      addInstanceIdentifierToLayoutRequests: false,
       footer: true,
       jsonObjectInDataResponse: false,
       processActions: true