diff --git a/.changeset/nine-beers-appear.md b/.changeset/nine-beers-appear.md
new file mode 100644
index 0000000000..ee0e81e200
--- /dev/null
+++ b/.changeset/nine-beers-appear.md
@@ -0,0 +1,8 @@
+---
+'@backstage/core-compat-api': minor
+'@backstage/frontend-plugin-api': minor
+'@backstage/frontend-test-utils': minor
+'@backstage/frontend-app-api': minor
+---
+
+Switched all core extensions to instead use the namespace `'app'`.
diff --git a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
index 862ef68bb5..ed6807514d 100644
--- a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
+++ b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
@@ -60,13 +60,13 @@ describe('collectLegacyRoutes', () => {
         extensions: [
           {
             id: 'page:score-card',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'score-board' },
           },
           {
             id: 'api:plugin.scoringdata.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
@@ -76,13 +76,13 @@ describe('collectLegacyRoutes', () => {
         extensions: [
           {
             id: 'page:stackstorm',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'stackstorm' },
           },
           {
             id: 'api:plugin.stackstorm.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
@@ -92,19 +92,19 @@ describe('collectLegacyRoutes', () => {
         extensions: [
           {
             id: 'page:puppetDb',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
             id: 'page:puppetDb/1',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
             id: 'api:plugin.puppetdb.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
@@ -163,13 +163,13 @@ describe('collectLegacyRoutes', () => {
         extensions: [
           {
             id: 'page:catalog',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'catalog' },
           },
           {
             id: 'page:catalog/1',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             defaultConfig: { path: 'catalog/:namespace/:kind/:name' },
             disabled: false,
           },
@@ -203,7 +203,7 @@ describe('collectLegacyRoutes', () => {
           {
             id: 'api:plugin.catalog.service',
             attachTo: {
-              id: 'core',
+              id: 'app',
               input: 'apis',
             },
             defaultConfig: undefined,
@@ -212,7 +212,7 @@ describe('collectLegacyRoutes', () => {
           {
             id: 'api:catalog-react.starred-entities',
             attachTo: {
-              id: 'core',
+              id: 'app',
               input: 'apis',
             },
             defaultConfig: undefined,
@@ -221,7 +221,7 @@ describe('collectLegacyRoutes', () => {
           {
             id: 'api:plugin.catalog.entity-presentation',
             attachTo: {
-              id: 'core',
+              id: 'app',
               input: 'apis',
             },
             defaultConfig: undefined,
@@ -234,7 +234,7 @@ describe('collectLegacyRoutes', () => {
         extensions: [
           {
             id: 'api:plugin.scoringdata.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
diff --git a/packages/core-compat-api/src/convertLegacyApp.test.tsx b/packages/core-compat-api/src/convertLegacyApp.test.tsx
index a8d6cb2dbc..ef65603c85 100644
--- a/packages/core-compat-api/src/convertLegacyApp.test.tsx
+++ b/packages/core-compat-api/src/convertLegacyApp.test.tsx
@@ -60,13 +60,13 @@ describe('convertLegacyApp', () => {
         extensions: [
           {
             id: 'page:score-card',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'score-board' },
           },
           {
             id: 'api:plugin.scoringdata.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
@@ -76,13 +76,13 @@ describe('convertLegacyApp', () => {
         extensions: [
           {
             id: 'page:stackstorm',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'stackstorm' },
           },
           {
             id: 'api:plugin.stackstorm.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
@@ -92,19 +92,19 @@ describe('convertLegacyApp', () => {
         extensions: [
           {
             id: 'page:puppetDb',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
             id: 'page:puppetDb/1',
-            attachTo: { id: 'core/routes', input: 'routes' },
+            attachTo: { id: 'app/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
             id: 'api:plugin.puppetdb.service',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             disabled: false,
           },
         ],
@@ -113,13 +113,13 @@ describe('convertLegacyApp', () => {
         id: undefined,
         extensions: [
           {
-            id: 'core/layout',
-            attachTo: { id: 'core', input: 'root' },
+            id: 'app/layout',
+            attachTo: { id: 'app', input: 'root' },
             disabled: false,
           },
           {
-            id: 'core/nav',
-            attachTo: { id: 'core/layout', input: 'nav' },
+            id: 'app/nav',
+            attachTo: { id: 'app/layout', input: 'nav' },
             disabled: true,
           },
         ],
diff --git a/packages/core-compat-api/src/convertLegacyApp.ts b/packages/core-compat-api/src/convertLegacyApp.ts
index 593a159875..72ce4b5e61 100644
--- a/packages/core-compat-api/src/convertLegacyApp.ts
+++ b/packages/core-compat-api/src/convertLegacyApp.ts
@@ -103,9 +103,9 @@ export function convertLegacyApp(
   const [routesEl] = routesEls;
 
   const CoreLayoutOverride = createExtension({
-    namespace: 'core',
+    namespace: 'app',
     name: 'layout',
-    attachTo: { id: 'core', input: 'root' },
+    attachTo: { id: 'app', input: 'root' },
     inputs: {
       content: createExtensionInput(
         {
@@ -129,9 +129,9 @@ export function convertLegacyApp(
     },
   });
   const CoreNavOverride = createExtension({
-    namespace: 'core',
+    namespace: 'app',
     name: 'nav',
-    attachTo: { id: 'core/layout', input: 'nav' },
+    attachTo: { id: 'app/layout', input: 'nav' },
     output: {},
     factory: () => ({}),
     disabled: true,
diff --git a/packages/frontend-app-api/src/extensions/Core.tsx b/packages/frontend-app-api/src/extensions/Core.tsx
index 99780e231c..ea722ce862 100644
--- a/packages/frontend-app-api/src/extensions/Core.tsx
+++ b/packages/frontend-app-api/src/extensions/Core.tsx
@@ -25,7 +25,7 @@ import {
 } from '@backstage/frontend-plugin-api';
 
 export const Core = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   attachTo: { id: 'root', input: 'default' }, // ignored
   inputs: {
     apis: createExtensionInput({
diff --git a/packages/frontend-app-api/src/extensions/CoreLayout.tsx b/packages/frontend-app-api/src/extensions/CoreLayout.tsx
index e4f86256f2..2d65dff73a 100644
--- a/packages/frontend-app-api/src/extensions/CoreLayout.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreLayout.tsx
@@ -23,9 +23,9 @@ import {
 import { SidebarPage } from '@backstage/core-components';
 
 export const CoreLayout = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   name: 'layout',
-  attachTo: { id: 'core/router', input: 'children' },
+  attachTo: { id: 'app/router', input: 'children' },
   inputs: {
     nav: createExtensionInput(
       {
diff --git a/packages/frontend-app-api/src/extensions/CoreNav.tsx b/packages/frontend-app-api/src/extensions/CoreNav.tsx
index 12e6b08989..9c0ac5e85a 100644
--- a/packages/frontend-app-api/src/extensions/CoreNav.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreNav.tsx
@@ -79,9 +79,9 @@ const SidebarNavItem = (
 };
 
 export const CoreNav = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   name: 'nav',
-  attachTo: { id: 'core/layout', input: 'nav' },
+  attachTo: { id: 'app/layout', input: 'nav' },
   inputs: {
     items: createExtensionInput({
       target: createNavItemExtension.targetDataRef,
diff --git a/packages/frontend-app-api/src/extensions/CoreRouter.tsx b/packages/frontend-app-api/src/extensions/CoreRouter.tsx
index 3abb7756bc..5c823c2e60 100644
--- a/packages/frontend-app-api/src/extensions/CoreRouter.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreRouter.tsx
@@ -35,9 +35,9 @@ import { BrowserRouter } from 'react-router-dom';
 import { RouteTracker } from '../routing/RouteTracker';
 
 export const CoreRouter = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   name: 'router',
-  attachTo: { id: 'core', input: 'root' },
+  attachTo: { id: 'app', input: 'root' },
   inputs: {
     signInPage: createExtensionInput(
       {
diff --git a/packages/frontend-app-api/src/extensions/CoreRoutes.tsx b/packages/frontend-app-api/src/extensions/CoreRoutes.tsx
index 155a5b60fa..d66c857f3b 100644
--- a/packages/frontend-app-api/src/extensions/CoreRoutes.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreRoutes.tsx
@@ -25,9 +25,9 @@ import {
 import { useRoutes } from 'react-router-dom';
 
 export const CoreRoutes = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   name: 'routes',
-  attachTo: { id: 'core/layout', input: 'content' },
+  attachTo: { id: 'app/layout', input: 'content' },
   inputs: {
     routes: createExtensionInput({
       path: coreExtensionData.routePath,
diff --git a/packages/frontend-app-api/src/routing/extractRouteInfoFromAppNode.test.ts b/packages/frontend-app-api/src/routing/extractRouteInfoFromAppNode.test.ts
index f0ce6ac590..1c332b331f 100644
--- a/packages/frontend-app-api/src/routing/extractRouteInfoFromAppNode.test.ts
+++ b/packages/frontend-app-api/src/routing/extractRouteInfoFromAppNode.test.ts
@@ -49,7 +49,7 @@ function createTestExtension(options: {
     name: options.name,
     attachTo: options.parent
       ? { id: `test/${options.parent}`, input: 'children' }
-      : { id: 'core/routes', input: 'routes' },
+      : { id: 'app/routes', input: 'routes' },
     output: {
       element: coreExtensionData.reactElement,
       path: coreExtensionData.routePath.optional(),
diff --git a/packages/frontend-app-api/src/tree/createAppTree.test.ts b/packages/frontend-app-api/src/tree/createAppTree.test.ts
index 15c8ab4750..9ee58fe2d2 100644
--- a/packages/frontend-app-api/src/tree/createAppTree.test.ts
+++ b/packages/frontend-app-api/src/tree/createAppTree.test.ts
@@ -24,18 +24,18 @@ import { createAppTree } from './createAppTree';
 
 const extBase = {
   id: 'test',
-  attachTo: { id: 'core', input: 'root' },
+  attachTo: { id: 'app', input: 'root' },
   output: {},
   factory: () => ({}),
 };
 
 describe('createAppTree', () => {
-  it('throws an error when a core extension is parametrized', () => {
+  it('throws an error when a app extension is parametrized', () => {
     const config = new MockConfigApi({
       app: {
         extensions: [
           {
-            core: {},
+            app: {},
           },
         ],
       },
@@ -48,17 +48,17 @@ describe('createAppTree', () => {
     ];
     expect(() =>
       createAppTree({ features, config, builtinExtensions: [] }),
-    ).toThrow("Configuration of the 'core' extension is forbidden");
+    ).toThrow("Configuration of the 'app' extension is forbidden");
   });
 
-  it('throws an error when a core extension is overridden', () => {
+  it('throws an error when a app extension is overridden', () => {
     const config = new MockConfigApi({});
     const features = [
       createExtensionOverrides({
         extensions: [
           createExtension({
-            name: 'core',
-            attachTo: { id: 'core/routes', input: 'route' },
+            name: 'app',
+            attachTo: { id: 'app/routes', input: 'route' },
             inputs: {},
             output: {},
             factory: () => ({}),
@@ -69,7 +69,7 @@ describe('createAppTree', () => {
     expect(() =>
       createAppTree({ features, config, builtinExtensions: [] }),
     ).toThrow(
-      "It is forbidden to override the following extension(s): 'core', which is done by one or more extension overrides",
+      "It is forbidden to override the following extension(s): 'app', which is done by one or more extension overrides",
     );
   });
 
diff --git a/packages/frontend-app-api/src/tree/createAppTree.ts b/packages/frontend-app-api/src/tree/createAppTree.ts
index 0f8ce09138..12c7f7fc3a 100644
--- a/packages/frontend-app-api/src/tree/createAppTree.ts
+++ b/packages/frontend-app-api/src/tree/createAppTree.ts
@@ -32,12 +32,12 @@ export interface CreateAppTreeOptions {
 /** @internal */
 export function createAppTree(options: CreateAppTreeOptions): AppTree {
   const tree = resolveAppTree(
-    'core',
+    'app',
     resolveAppNodeSpecs({
       features: options.features,
       builtinExtensions: options.builtinExtensions,
       parameters: readAppExtensionsConfig(options.config),
-      forbidden: new Set(['core']),
+      forbidden: new Set(['app']),
     }),
   );
   instantiateAppNodeTree(tree.root);
diff --git a/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts b/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts
index 49f6203ce4..7855b87df2 100644
--- a/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts
+++ b/packages/frontend-app-api/src/tree/instantiateAppNodeTree.test.ts
@@ -37,7 +37,7 @@ const inputMirrorDataRef = createExtensionDataRef<unknown>('mirror');
 
 const simpleExtension = resolveExtensionDefinition(
   createExtension({
-    namespace: 'core',
+    namespace: 'app',
     name: 'test',
     attachTo: { id: 'ignored', input: 'ignored' },
     output: {
@@ -256,7 +256,7 @@ describe('createAppNodeInstance', () => {
       node: makeNode(
         resolveExtensionDefinition(
           createExtension({
-            namespace: 'core',
+            namespace: 'app',
             name: 'test',
             attachTo: { id: 'ignored', input: 'ignored' },
             inputs: {
@@ -300,17 +300,17 @@ describe('createAppNodeInstance', () => {
     expect(Array.from(instance.getDataRefs())).toEqual([inputMirrorDataRef]);
     expect(instance.getData(inputMirrorDataRef)).toMatchObject({
       optionalSingletonPresent: {
-        node: { spec: { id: 'core/test' } },
+        node: { spec: { id: 'app/test' } },
         output: { test: 'optionalSingletonPresent' },
       },
       singleton: {
-        node: { spec: { id: 'core/test' } },
+        node: { spec: { id: 'app/test' } },
         output: { test: 'singleton', other: 2 },
       },
       many: [
-        { node: { spec: { id: 'core/test' } }, output: { test: 'many1' } },
+        { node: { spec: { id: 'app/test' } }, output: { test: 'many1' } },
         {
-          node: { spec: { id: 'core/test' } },
+          node: { spec: { id: 'app/test' } },
           output: { test: 'many2', other: 3 },
         },
       ],
@@ -324,7 +324,7 @@ describe('createAppNodeInstance', () => {
         attachments: new Map(),
       }),
     ).toThrow(
-      "Invalid configuration for extension 'core/test'; caused by Error: Expected number, received string at 'other'",
+      "Invalid configuration for extension 'app/test'; caused by Error: Expected number, received string at 'other'",
     );
   });
 
@@ -334,7 +334,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               output: {},
@@ -349,7 +349,7 @@ describe('createAppNodeInstance', () => {
         attachments: new Map(),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test'; caused by NopeError: NOPE",
+      "Failed to instantiate extension 'app/test'; caused by NopeError: NOPE",
     );
   });
 
@@ -359,7 +359,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               output: {
@@ -375,7 +375,7 @@ describe('createAppNodeInstance', () => {
         attachments: new Map(),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', duplicate extension data 'test' received via output 'test2'",
+      "Failed to instantiate extension 'app/test', duplicate extension data 'test' received via output 'test2'",
     );
   });
 
@@ -385,7 +385,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               output: {
@@ -400,7 +400,7 @@ describe('createAppNodeInstance', () => {
         attachments: new Map(),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', unknown output provided via 'nonexistent'",
+      "Failed to instantiate extension 'app/test', unknown output provided via 'nonexistent'",
     );
   });
 
@@ -410,7 +410,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               inputs: {
@@ -429,7 +429,7 @@ describe('createAppNodeInstance', () => {
         attachments: new Map(),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', input 'singleton' is required but was not received",
+      "Failed to instantiate extension 'app/test', input 'singleton' is required but was not received",
     );
   });
 
@@ -457,7 +457,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               inputs: {
@@ -472,7 +472,7 @@ describe('createAppNodeInstance', () => {
         ),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', received undeclared input 'undeclared' from extension 'core/test'",
+      "Failed to instantiate extension 'app/test', received undeclared input 'undeclared' from extension 'app/test'",
     );
   });
 
@@ -495,7 +495,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               output: {},
@@ -505,7 +505,7 @@ describe('createAppNodeInstance', () => {
         ),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', received undeclared inputs 'undeclared1' from extension 'core/test' and 'undeclared2' from extensions 'core/test', 'core/test'",
+      "Failed to instantiate extension 'app/test', received undeclared inputs 'undeclared1' from extension 'app/test' and 'undeclared2' from extensions 'app/test', 'app/test'",
     );
   });
 
@@ -524,7 +524,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               inputs: {
@@ -542,7 +542,7 @@ describe('createAppNodeInstance', () => {
         ),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', expected exactly one 'singleton' input but received multiple: 'core/test', 'core/test'",
+      "Failed to instantiate extension 'app/test', expected exactly one 'singleton' input but received multiple: 'app/test', 'app/test'",
     );
   });
 
@@ -561,7 +561,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               inputs: {
@@ -579,7 +579,7 @@ describe('createAppNodeInstance', () => {
         ),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', expected at most one 'singleton' input but received multiple: 'core/test', 'core/test'",
+      "Failed to instantiate extension 'app/test', expected at most one 'singleton' input but received multiple: 'app/test', 'app/test'",
     );
   });
 
@@ -592,7 +592,7 @@ describe('createAppNodeInstance', () => {
         node: makeNode(
           resolveExtensionDefinition(
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'test',
               attachTo: { id: 'ignored', input: 'ignored' },
               inputs: {
@@ -610,7 +610,7 @@ describe('createAppNodeInstance', () => {
         ),
       }),
     ).toThrow(
-      "Failed to instantiate extension 'core/test', input 'singleton' did not receive required extension data 'other' from extension 'core/test'",
+      "Failed to instantiate extension 'app/test', input 'singleton' did not receive required extension data 'other' from extension 'app/test'",
     );
   });
 });
diff --git a/packages/frontend-app-api/src/tree/readAppExtensionsConfig.test.ts b/packages/frontend-app-api/src/tree/readAppExtensionsConfig.test.ts
index 504d5a6197..4531947f9a 100644
--- a/packages/frontend-app-api/src/tree/readAppExtensionsConfig.test.ts
+++ b/packages/frontend-app-api/src/tree/readAppExtensionsConfig.test.ts
@@ -25,18 +25,18 @@ describe('readAppExtensionsConfig', () => {
   it('should disable extension with shorthand notation', () => {
     expect(
       readAppExtensionsConfig(
-        new ConfigReader({ app: { extensions: [{ 'core/router': false }] } }),
+        new ConfigReader({ app: { extensions: [{ 'app/router': false }] } }),
       ),
     ).toEqual([
       {
-        id: 'core/router',
+        id: 'app/router',
         disabled: true,
       },
     ]);
     expect(
       readAppExtensionsConfig(
         new ConfigReader({
-          app: { extensions: [{ 'core/router': { disabled: true } }] },
+          app: { extensions: [{ 'app/router': { disabled: true } }] },
         }),
       ),
     ).toEqual([
@@ -44,7 +44,7 @@ describe('readAppExtensionsConfig', () => {
         at: undefined,
         config: undefined,
         disabled: true,
-        id: 'core/router',
+        id: 'app/router',
       },
     ]);
   });
@@ -52,33 +52,33 @@ describe('readAppExtensionsConfig', () => {
   it('should enable extension with shorthand notation', () => {
     expect(
       readAppExtensionsConfig(
-        new ConfigReader({ app: { extensions: ['core/router'] } }),
+        new ConfigReader({ app: { extensions: ['app/router'] } }),
       ),
     ).toEqual([
       {
-        id: 'core/router',
+        id: 'app/router',
         disabled: false,
       },
     ]);
     expect(
       readAppExtensionsConfig(
-        new ConfigReader({ app: { extensions: [{ 'core/router': true }] } }),
+        new ConfigReader({ app: { extensions: [{ 'app/router': true }] } }),
       ),
     ).toEqual([
       {
-        id: 'core/router',
+        id: 'app/router',
         disabled: false,
       },
     ]);
     expect(
       readAppExtensionsConfig(
         new ConfigReader({
-          app: { extensions: [{ 'core/router': { disabled: false } }] },
+          app: { extensions: [{ 'app/router': { disabled: false } }] },
         }),
       ),
     ).toEqual([
       {
-        id: 'core/router',
+        id: 'app/router',
         disabled: false,
       },
     ]);
@@ -89,12 +89,12 @@ describe('readAppExtensionsConfig', () => {
       readAppExtensionsConfig(
         new ConfigReader({
           app: {
-            extensions: [{ 'core/router': 'some-string' }],
+            extensions: [{ 'app/router': 'some-string' }],
           },
         }),
       ),
     ).toThrow(
-      'Invalid extension configuration at app.extensions[0][core/router], value must be a boolean or object',
+      'Invalid extension configuration at app.extensions[0][app/router], value must be a boolean or object',
     );
   });
 
@@ -156,8 +156,8 @@ describe('expandShorthandExtensionParameters', () => {
   });
 
   it('supports string key', () => {
-    expect(run('core/router')).toEqual({
-      id: 'core/router',
+    expect(run('app/router')).toEqual({
+      id: 'app/router',
       disabled: false,
     });
     expect(() => run('')).toThrowErrorMatchingInlineSnapshot(
@@ -170,96 +170,96 @@ describe('expandShorthandExtensionParameters', () => {
 
   it('supports null value', () => {
     // this is the result of typing:
-    // - core/router:
+    // - app/router:
     // The missing value is interpreted as null by the yaml parser so we deal with that
-    expect(run({ 'core/router': null })).toEqual({
-      id: 'core/router',
+    expect(run({ 'app/router': null })).toEqual({
+      id: 'app/router',
       disabled: false,
     });
   });
 
   it('supports boolean value', () => {
-    expect(run({ 'core/router': true })).toEqual({
-      id: 'core/router',
+    expect(run({ 'app/router': true })).toEqual({
+      id: 'app/router',
       disabled: false,
     });
-    expect(run({ 'core/router': false })).toEqual({
-      id: 'core/router',
+    expect(run({ 'app/router': false })).toEqual({
+      id: 'app/router',
       disabled: true,
     });
   });
 
   it('should not support string values', () => {
     expect(() =>
-      run({ 'core/router': 'example-package#MyRouter' }),
+      run({ 'app/router': 'example-package#MyRouter' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid extension configuration at app.extensions[1][core/router], value must be a boolean or object"`,
+      `"Invalid extension configuration at app.extensions[1][app/router], value must be a boolean or object"`,
     );
   });
 
   it('supports object id only in the key', () => {
     expect(() =>
-      run({ 'core/router': { id: 'some.id' } }),
+      run({ 'app/router': { id: 'some.id' } }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid extension configuration at app.extensions[1][core/router].id, unknown parameter; expected one of 'attachTo', 'disabled', 'config'"`,
+      `"Invalid extension configuration at app.extensions[1][app/router].id, unknown parameter; expected one of 'attachTo', 'disabled', 'config'"`,
     );
   });
 
   it('supports object attachTo', () => {
     expect(
       run({
-        'core/router': { attachTo: { id: 'other.root', input: 'inputs' } },
+        'app/router': { attachTo: { id: 'other.root', input: 'inputs' } },
       }),
     ).toEqual({
-      id: 'core/router',
+      id: 'app/router',
       attachTo: { id: 'other.root', input: 'inputs' },
     });
     expect(() =>
       run({
-        'core/router': {
+        'app/router': {
           id: 'other-id',
         },
       }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid extension configuration at app.extensions[1][core/router].id, unknown parameter; expected one of 'attachTo', 'disabled', 'config'"`,
+      `"Invalid extension configuration at app.extensions[1][app/router].id, unknown parameter; expected one of 'attachTo', 'disabled', 'config'"`,
     );
   });
 
   it('supports object disabled', () => {
-    expect(run({ 'core/router': { disabled: true } })).toEqual({
-      id: 'core/router',
+    expect(run({ 'app/router': { disabled: true } })).toEqual({
+      id: 'app/router',
       disabled: true,
     });
-    expect(run({ 'core/router': { disabled: false } })).toEqual({
-      id: 'core/router',
+    expect(run({ 'app/router': { disabled: false } })).toEqual({
+      id: 'app/router',
       disabled: false,
     });
     expect(() =>
-      run({ 'core/router': { disabled: 0 } }),
+      run({ 'app/router': { disabled: 0 } }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid extension configuration at app.extensions[1][core/router].disabled, must be a boolean"`,
+      `"Invalid extension configuration at app.extensions[1][app/router].disabled, must be a boolean"`,
     );
   });
 
   it('supports object config', () => {
     expect(
-      run({ 'core/router': { config: { disableRedirects: true } } }),
+      run({ 'app/router': { config: { disableRedirects: true } } }),
     ).toEqual({
-      id: 'core/router',
+      id: 'app/router',
       config: { disableRedirects: true },
     });
     expect(() =>
-      run({ 'core/router': { config: 0 } }),
+      run({ 'app/router': { config: 0 } }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid extension configuration at app.extensions[1][core/router].config, must be an object"`,
+      `"Invalid extension configuration at app.extensions[1][app/router].config, must be an object"`,
     );
   });
 
   it('rejects unknown object keys', () => {
     expect(() =>
-      run({ 'core/router': { foo: { settings: true } } }),
+      run({ 'app/router': { foo: { settings: true } } }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid extension configuration at app.extensions[1][core/router].foo, unknown parameter; expected one of 'attachTo', 'disabled', 'config'"`,
+      `"Invalid extension configuration at app.extensions[1][app/router].foo, unknown parameter; expected one of 'attachTo', 'disabled', 'config'"`,
     );
   });
 });
diff --git a/packages/frontend-app-api/src/tree/resolveAppTree.test.ts b/packages/frontend-app-api/src/tree/resolveAppTree.test.ts
index 4fca671554..f964fceb50 100644
--- a/packages/frontend-app-api/src/tree/resolveAppTree.test.ts
+++ b/packages/frontend-app-api/src/tree/resolveAppTree.test.ts
@@ -36,19 +36,19 @@ const baseSpec = {
 
 describe('buildAppTree', () => {
   it('should fail to create an empty tree', () => {
-    expect(() => resolveAppTree('core', [])).toThrow(
-      "No root node with id 'core' found in app tree",
+    expect(() => resolveAppTree('app', [])).toThrow(
+      "No root node with id 'app' found in app tree",
     );
   });
 
   it('should create a tree with only one node', () => {
-    const tree = resolveAppTree('core', [{ ...baseSpec, id: 'core' }]);
+    const tree = resolveAppTree('app', [{ ...baseSpec, id: 'app' }]);
     expect(tree.root).toEqual({
-      spec: { ...baseSpec, id: 'core' },
+      spec: { ...baseSpec, id: 'app' },
       edges: { attachments: new Map() },
     });
     expect(Array.from(tree.orphans)).toEqual([]);
-    expect(Array.from(tree.nodes.keys())).toEqual(['core']);
+    expect(Array.from(tree.nodes.keys())).toEqual(['app']);
   });
 
   it('should create a tree', () => {
@@ -159,7 +159,7 @@ describe('buildAppTree', () => {
 
   it('throws an error when duplicated extensions are detected', () => {
     expect(() =>
-      resolveAppTree('core', [
+      resolveAppTree('app', [
         { ...baseSpec, id: 'a' },
         { ...baseSpec, id: 'a' },
       ]),
diff --git a/packages/frontend-app-api/src/wiring/createApp.test.tsx b/packages/frontend-app-api/src/wiring/createApp.test.tsx
index 1cbe3a65ba..d5a206e7fb 100644
--- a/packages/frontend-app-api/src/wiring/createApp.test.tsx
+++ b/packages/frontend-app-api/src/wiring/createApp.test.tsx
@@ -169,7 +169,7 @@ describe('createApp', () => {
           extensions: [
             createExtension({
               name: 'first',
-              attachTo: { id: 'core', input: 'root' },
+              attachTo: { id: 'app', input: 'root' },
               output: { element: coreExtensionData.reactElement },
               factory() {
                 const Component = () => {
@@ -193,9 +193,9 @@ describe('createApp', () => {
           featureFlags: [{ name: 'test-2' }],
           extensions: [
             createExtension({
-              namespace: 'core',
+              namespace: 'app',
               name: 'router',
-              attachTo: { id: 'core', input: 'root' },
+              attachTo: { id: 'app', input: 'root' },
               disabled: true,
               output: {},
               factory: () => ({}),
@@ -242,24 +242,24 @@ describe('createApp', () => {
     const { tree } = appTreeApi!.getTree();
 
     expect(String(tree.root)).toMatchInlineSnapshot(`
-      "<core out=[core.reactElement]>
+      "<app out=[core.reactElement]>
         root [
-          <core/router out=[core.reactElement]>
+          <app/router out=[core.reactElement]>
             children [
-              <core/layout out=[core.reactElement]>
+              <app/layout out=[core.reactElement]>
                 content [
-                  <core/routes out=[core.reactElement]>
+                  <app/routes out=[core.reactElement]>
                     routes [
                       <page:my-plugin out=[core.routing.path, core.routing.ref, core.reactElement] />
                     ]
-                  </core/routes>
+                  </app/routes>
                 ]
                 nav [
-                  <core/nav out=[core.reactElement] />
+                  <app/nav out=[core.reactElement] />
                 ]
-              </core/layout>
+              </app/layout>
             ]
-          </core/router>
+          </app/router>
         ]
         components [
           <component:core.components.progress out=[core.component.component] />
@@ -289,7 +289,7 @@ describe('createApp', () => {
           <api:core.auth.atlassian out=[core.api.factory] />
           <api:plugin.permission.api out=[core.api.factory] />
         ]
-      </core>"
+      </app>"
     `);
   });
 });
diff --git a/packages/frontend-app-api/src/wiring/createApp.tsx b/packages/frontend-app-api/src/wiring/createApp.tsx
index 337da91708..09a7034ffb 100644
--- a/packages/frontend-app-api/src/wiring/createApp.tsx
+++ b/packages/frontend-app-api/src/wiring/createApp.tsx
@@ -172,7 +172,7 @@ export function createExtensionTree(options: {
       );
     },
     getRootRoutes(): JSX.Element[] {
-      return this.getExtensionAttachments('core/routes', 'routes').map(node => {
+      return this.getExtensionAttachments('app/routes', 'routes').map(node => {
         const path = node.getData(coreExtensionData.routePath);
         const element = node.getData(coreExtensionData.reactElement);
         const routeRef = node.getData(coreExtensionData.routeRef);
@@ -199,7 +199,7 @@ export function createExtensionTree(options: {
         );
       };
 
-      return this.getExtensionAttachments('core/nav', 'items')
+      return this.getExtensionAttachments('app/nav', 'items')
         .map((node, index) => {
           const target = node.getData(createNavItemExtension.targetDataRef);
           if (!target) {
diff --git a/packages/frontend-plugin-api/src/components/ExtensionBoundary.test.tsx b/packages/frontend-plugin-api/src/components/ExtensionBoundary.test.tsx
index 669335d577..66fb3901fc 100644
--- a/packages/frontend-plugin-api/src/components/ExtensionBoundary.test.tsx
+++ b/packages/frontend-plugin-api/src/components/ExtensionBoundary.test.tsx
@@ -27,7 +27,7 @@ const wrapInBoundaryExtension = (element: JSX.Element) => {
   const routeRef = createRouteRef();
   return createExtension({
     name: 'test',
-    attachTo: { id: 'core/routes', input: 'routes' },
+    attachTo: { id: 'app/routes', input: 'routes' },
     output: {
       element: coreExtensionData.reactElement,
       path: coreExtensionData.routePath,
diff --git a/packages/frontend-plugin-api/src/extensions/createApiExtension.test.ts b/packages/frontend-plugin-api/src/extensions/createApiExtension.test.ts
index d3bd84bc7f..0636d0d79d 100644
--- a/packages/frontend-plugin-api/src/extensions/createApiExtension.test.ts
+++ b/packages/frontend-plugin-api/src/extensions/createApiExtension.test.ts
@@ -35,7 +35,7 @@ describe('createApiExtension', () => {
       version: 'v1',
       kind: 'api',
       namespace: 'test',
-      attachTo: { id: 'core', input: 'apis' },
+      attachTo: { id: 'app', input: 'apis' },
       disabled: false,
       configSchema: undefined,
       inputs: {},
@@ -71,7 +71,7 @@ describe('createApiExtension', () => {
       version: 'v1',
       kind: 'api',
       namespace: 'test',
-      attachTo: { id: 'core', input: 'apis' },
+      attachTo: { id: 'app', input: 'apis' },
       disabled: false,
       configSchema: undefined,
       inputs: {},
diff --git a/packages/frontend-plugin-api/src/extensions/createApiExtension.ts b/packages/frontend-plugin-api/src/extensions/createApiExtension.ts
index e941c4f2a0..1680332960 100644
--- a/packages/frontend-plugin-api/src/extensions/createApiExtension.ts
+++ b/packages/frontend-plugin-api/src/extensions/createApiExtension.ts
@@ -55,7 +55,7 @@ export function createApiExtension<
     // Since ApiRef IDs use a global namespace we use the namespace here in order to override
     // potential plugin IDs and always end up with the format `api:<api-ref-id>`
     namespace: apiRef.id,
-    attachTo: { id: 'core', input: 'apis' },
+    attachTo: { id: 'app', input: 'apis' },
     inputs: extensionInputs,
     configSchema,
     output: {
diff --git a/packages/frontend-plugin-api/src/extensions/createComponentExtension.tsx b/packages/frontend-plugin-api/src/extensions/createComponentExtension.tsx
index 175b37b144..2efa106750 100644
--- a/packages/frontend-plugin-api/src/extensions/createComponentExtension.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createComponentExtension.tsx
@@ -54,7 +54,7 @@ export function createComponentExtension<
     kind: 'component',
     namespace: options.ref.id,
     name: options.name,
-    attachTo: { id: 'core', input: 'components' },
+    attachTo: { id: 'app', input: 'components' },
     inputs: options.inputs,
     disabled: options.disabled,
     configSchema: options.configSchema,
diff --git a/packages/frontend-plugin-api/src/extensions/createNavItemExtension.tsx b/packages/frontend-plugin-api/src/extensions/createNavItemExtension.tsx
index d2062c74c5..4b92d4dace 100644
--- a/packages/frontend-plugin-api/src/extensions/createNavItemExtension.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createNavItemExtension.tsx
@@ -35,7 +35,7 @@ export function createNavItemExtension(options: {
     namespace,
     name,
     kind: 'nav-item',
-    attachTo: { id: 'core/nav', input: 'items' },
+    attachTo: { id: 'app/nav', input: 'items' },
     configSchema: createSchemaFromZod(z =>
       z.object({
         title: z.string().default(title),
diff --git a/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.test.tsx b/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.test.tsx
index 265b381094..90e1448448 100644
--- a/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.test.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.test.tsx
@@ -34,7 +34,7 @@ describe('createNavLogoExtension', () => {
       version: 'v1',
       kind: 'nav-logo',
       name: 'test',
-      attachTo: { id: 'core/nav', input: 'logos' },
+      attachTo: { id: 'app/nav', input: 'logos' },
       disabled: false,
       inputs: {},
       output: {
diff --git a/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.tsx b/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.tsx
index 8e2454ddc3..3d66b26d6b 100644
--- a/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createNavLogoExtension.tsx
@@ -31,7 +31,7 @@ export function createNavLogoExtension(options: {
     kind: 'nav-logo',
     name: options?.name,
     namespace: options?.namespace,
-    attachTo: { id: 'core/nav', input: 'logos' },
+    attachTo: { id: 'app/nav', input: 'logos' },
     output: {
       logos: createNavLogoExtension.logoElementsDataRef,
     },
diff --git a/packages/frontend-plugin-api/src/extensions/createPageExtension.test.tsx b/packages/frontend-plugin-api/src/extensions/createPageExtension.test.tsx
index 28f74d544c..2de72296ac 100644
--- a/packages/frontend-plugin-api/src/extensions/createPageExtension.test.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createPageExtension.test.tsx
@@ -45,7 +45,7 @@ describe('createPageExtension', () => {
       version: 'v1',
       name: 'test',
       kind: 'page',
-      attachTo: { id: 'core/routes', input: 'routes' },
+      attachTo: { id: 'app/routes', input: 'routes' },
       configSchema: expect.anything(),
       disabled: false,
       inputs: {},
@@ -102,7 +102,7 @@ describe('createPageExtension', () => {
       version: 'v1',
       name: 'test',
       kind: 'page',
-      attachTo: { id: 'core/routes', input: 'routes' },
+      attachTo: { id: 'app/routes', input: 'routes' },
       configSchema: expect.anything(),
       disabled: false,
       inputs: {},
diff --git a/packages/frontend-plugin-api/src/extensions/createPageExtension.tsx b/packages/frontend-plugin-api/src/extensions/createPageExtension.tsx
index 3b936ef210..dfe549f32b 100644
--- a/packages/frontend-plugin-api/src/extensions/createPageExtension.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createPageExtension.tsx
@@ -67,7 +67,7 @@ export function createPageExtension<
     kind: 'page',
     namespace: options.namespace,
     name: options.name,
-    attachTo: options.attachTo ?? { id: 'core/routes', input: 'routes' },
+    attachTo: options.attachTo ?? { id: 'app/routes', input: 'routes' },
     configSchema,
     inputs: options.inputs,
     disabled: options.disabled,
diff --git a/packages/frontend-plugin-api/src/extensions/createSignInPageExtension.tsx b/packages/frontend-plugin-api/src/extensions/createSignInPageExtension.tsx
index ee993b1bc0..543a5447ad 100644
--- a/packages/frontend-plugin-api/src/extensions/createSignInPageExtension.tsx
+++ b/packages/frontend-plugin-api/src/extensions/createSignInPageExtension.tsx
@@ -50,7 +50,7 @@ export function createSignInPageExtension<
     kind: 'sign-in-page',
     namespace: options?.namespace,
     name: options?.name,
-    attachTo: options.attachTo ?? { id: 'core/router', input: 'signInPage' },
+    attachTo: options.attachTo ?? { id: 'app/router', input: 'signInPage' },
     configSchema: options.configSchema,
     inputs: options.inputs,
     disabled: options.disabled,
diff --git a/packages/frontend-plugin-api/src/extensions/createThemeExtension.ts b/packages/frontend-plugin-api/src/extensions/createThemeExtension.ts
index dd6c2f742f..cc6dbdabe9 100644
--- a/packages/frontend-plugin-api/src/extensions/createThemeExtension.ts
+++ b/packages/frontend-plugin-api/src/extensions/createThemeExtension.ts
@@ -23,7 +23,7 @@ export function createThemeExtension(theme: AppTheme) {
     kind: 'theme',
     namespace: 'app',
     name: theme.id,
-    attachTo: { id: 'core', input: 'themes' },
+    attachTo: { id: 'app', input: 'themes' },
     output: {
       theme: createThemeExtension.themeDataRef,
     },
diff --git a/packages/frontend-plugin-api/src/extensions/createTranslationExtension.test.ts b/packages/frontend-plugin-api/src/extensions/createTranslationExtension.test.ts
index ea57fdbc8f..3712da7185 100644
--- a/packages/frontend-plugin-api/src/extensions/createTranslationExtension.test.ts
+++ b/packages/frontend-plugin-api/src/extensions/createTranslationExtension.test.ts
@@ -44,7 +44,7 @@ describe('createTranslationExtension', () => {
       version: 'v1',
       kind: 'translation',
       namespace: 'test',
-      attachTo: { id: 'core', input: 'translations' },
+      attachTo: { id: 'app', input: 'translations' },
       disabled: false,
       inputs: {},
       output: {
@@ -81,7 +81,7 @@ describe('createTranslationExtension', () => {
       version: 'v1',
       kind: 'translation',
       namespace: 'test',
-      attachTo: { id: 'core', input: 'translations' },
+      attachTo: { id: 'app', input: 'translations' },
       disabled: false,
       inputs: {},
       output: {
@@ -119,7 +119,7 @@ describe('createTranslationExtension', () => {
       kind: 'translation',
       namespace: 'test',
       name: 'sv',
-      attachTo: { id: 'core', input: 'translations' },
+      attachTo: { id: 'app', input: 'translations' },
       disabled: false,
       inputs: {},
       output: {
diff --git a/packages/frontend-plugin-api/src/extensions/createTranslationExtension.ts b/packages/frontend-plugin-api/src/extensions/createTranslationExtension.ts
index 3db29cdeb5..8497a64b88 100644
--- a/packages/frontend-plugin-api/src/extensions/createTranslationExtension.ts
+++ b/packages/frontend-plugin-api/src/extensions/createTranslationExtension.ts
@@ -26,7 +26,7 @@ export function createTranslationExtension(options: {
     kind: 'translation',
     namespace: options.resource.id,
     name: options.name,
-    attachTo: { id: 'core', input: 'translations' },
+    attachTo: { id: 'app', input: 'translations' },
     output: {
       resource: createTranslationExtension.translationDataRef,
     },
diff --git a/packages/frontend-plugin-api/src/wiring/createExtensionOverrides.test.ts b/packages/frontend-plugin-api/src/wiring/createExtensionOverrides.test.ts
index 6f5f19e29e..de2d2f9a92 100644
--- a/packages/frontend-plugin-api/src/wiring/createExtensionOverrides.test.ts
+++ b/packages/frontend-plugin-api/src/wiring/createExtensionOverrides.test.ts
@@ -38,13 +38,13 @@ describe('createExtensionOverrides', () => {
         extensions: [
           createExtension({
             name: 'a',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             output: {},
             factory: () => ({}),
           }),
           createExtension({
             namespace: 'b',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             output: {},
             factory: () => ({}),
           }),
@@ -52,7 +52,7 @@ describe('createExtensionOverrides', () => {
             kind: 'k',
             namespace: 'c',
             name: 'n',
-            attachTo: { id: 'core', input: 'apis' },
+            attachTo: { id: 'app', input: 'apis' },
             output: {},
             factory: () => ({}),
           }),
@@ -65,7 +65,7 @@ describe('createExtensionOverrides', () => {
           {
             "$$type": "@backstage/Extension",
             "attachTo": {
-              "id": "core",
+              "id": "app",
               "input": "apis",
             },
             "configSchema": undefined,
@@ -79,7 +79,7 @@ describe('createExtensionOverrides', () => {
           {
             "$$type": "@backstage/Extension",
             "attachTo": {
-              "id": "core",
+              "id": "app",
               "input": "apis",
             },
             "configSchema": undefined,
@@ -93,7 +93,7 @@ describe('createExtensionOverrides', () => {
           {
             "$$type": "@backstage/Extension",
             "attachTo": {
-              "id": "core",
+              "id": "app",
               "input": "apis",
             },
             "configSchema": undefined,
@@ -116,7 +116,7 @@ describe('createExtensionOverrides', () => {
       extensions: [
         createExtension({
           namespace: 'a',
-          attachTo: { id: 'core', input: 'apis' },
+          attachTo: { id: 'app', input: 'apis' },
           output: {},
           factory: () => ({}),
         }),
diff --git a/packages/frontend-plugin-api/src/wiring/createPlugin.test.ts b/packages/frontend-plugin-api/src/wiring/createPlugin.test.ts
index c7f31eb60d..cb02048bdc 100644
--- a/packages/frontend-plugin-api/src/wiring/createPlugin.test.ts
+++ b/packages/frontend-plugin-api/src/wiring/createPlugin.test.ts
@@ -102,7 +102,7 @@ const Child2 = createExtension({
 
 const outputExtension = createExtension({
   name: 'output',
-  attachTo: { id: 'core', input: 'root' },
+  attachTo: { id: 'app', input: 'root' },
   inputs: {
     names: createExtensionInput({
       name: nameExtensionDataRef,
@@ -150,7 +150,7 @@ describe('createPlugin', () => {
     await renderWithEffects(
       createTestAppRoot({
         features: [plugin],
-        config: { app: { extensions: [{ 'core/router': false }] } },
+        config: { app: { extensions: [{ 'app/router': false }] } },
       }),
     );
 
@@ -172,7 +172,7 @@ describe('createPlugin', () => {
         config: {
           app: {
             extensions: [
-              { 'core/router': false },
+              { 'app/router': false },
               {
                 'test/2': {
                   config: { name: 'extension-2-renamed' },
@@ -210,7 +210,7 @@ describe('createPlugin', () => {
         features: [plugin],
         config: {
           app: {
-            extensions: [{ 'core/router': false }],
+            extensions: [{ 'app/router': false }],
           },
         },
       }),
diff --git a/packages/frontend-test-utils/src/app/createExtensionTester.test.tsx b/packages/frontend-test-utils/src/app/createExtensionTester.test.tsx
index 04da2b7e89..40baaa3ac9 100644
--- a/packages/frontend-test-utils/src/app/createExtensionTester.test.tsx
+++ b/packages/frontend-test-utils/src/app/createExtensionTester.test.tsx
@@ -64,7 +64,7 @@ describe('createExtensionTester', () => {
     });
     const tester = createExtensionTester(extension);
     expect(() => tester.render()).toThrow(
-      "Failed to instantiate extension 'core/routes', input 'routes' did not receive required extension data 'core.reactElement' from extension 'test'",
+      "Failed to instantiate extension 'app/routes', input 'routes' did not receive required extension data 'core.reactElement' from extension 'test'",
     );
   });
 
@@ -82,7 +82,7 @@ describe('createExtensionTester', () => {
     const detailsPageExtension = createExtension({
       ...defaultDefinition,
       name: 'details',
-      attachTo: { id: 'core/routes', input: 'routes' },
+      attachTo: { id: 'app/routes', input: 'routes' },
       output: {
         path: coreExtensionData.routePath,
         element: coreExtensionData.reactElement,
@@ -130,7 +130,7 @@ describe('createExtensionTester', () => {
     const detailsPageExtension = createExtension({
       ...defaultDefinition,
       name: 'details',
-      attachTo: { id: 'core/routes', input: 'routes' },
+      attachTo: { id: 'app/routes', input: 'routes' },
       configSchema: createSchemaFromZod(z =>
         z.object({ title: z.string().optional() }),
       ),
diff --git a/packages/frontend-test-utils/src/app/createExtensionTester.tsx b/packages/frontend-test-utils/src/app/createExtensionTester.tsx
index fdac4746d5..aae2e5ed32 100644
--- a/packages/frontend-test-utils/src/app/createExtensionTester.tsx
+++ b/packages/frontend-test-utils/src/app/createExtensionTester.tsx
@@ -64,9 +64,9 @@ const NavItem = (props: {
 };
 
 const TestCoreNavExtension = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   name: 'nav',
-  attachTo: { id: 'core/layout', input: 'nav' },
+  attachTo: { id: 'app/layout', input: 'nav' },
   inputs: {
     items: createExtensionInput({
       target: createNavItemExtension.targetDataRef,
@@ -150,9 +150,9 @@ const AuthenticationProvider = (props: {
 };
 
 const TestCoreRouterExtension = createExtension({
-  namespace: 'core',
+  namespace: 'app',
   name: 'router',
-  attachTo: { id: 'core', input: 'root' },
+  attachTo: { id: 'app', input: 'root' },
   inputs: {
     signInPage: createExtensionInput(
       {
@@ -195,10 +195,10 @@ export class ExtensionTester {
   ): ExtensionTester {
     const tester = new ExtensionTester();
     const { output, factory, ...rest } = toInternalExtensionDefinition(subject);
-    // attaching to core/routes to render as index route
+    // attaching to app/routes to render as index route
     const extension = createExtension({
       ...rest,
-      attachTo: { id: 'core/routes', input: 'routes' },
+      attachTo: { id: 'app/routes', input: 'routes' },
       output: {
         ...output,
         path: coreExtensionData.routePath,
diff --git a/packages/frontend-test-utils/src/app/renderInTestApp.tsx b/packages/frontend-test-utils/src/app/renderInTestApp.tsx
index f4011535a4..0cd05741b0 100644
--- a/packages/frontend-test-utils/src/app/renderInTestApp.tsx
+++ b/packages/frontend-test-utils/src/app/renderInTestApp.tsx
@@ -27,7 +27,7 @@ import { createExtensionTester } from './createExtensionTester';
 export function renderInTestApp(element: JSX.Element) {
   const extension = createExtension({
     namespace: 'test',
-    attachTo: { id: 'core', input: 'root' },
+    attachTo: { id: 'app', input: 'root' },
     output: {
       element: coreExtensionData.reactElement,
     },