diff --git a/packages/core-app-api/src/apis/implementations/AlertApi/AlertApiForwarder.ts b/packages/core-app-api/src/apis/implementations/AlertApi/AlertApiForwarder.ts
index 8bab1b539d..28cb5bc068 100644
--- a/packages/core-app-api/src/apis/implementations/AlertApi/AlertApiForwarder.ts
+++ b/packages/core-app-api/src/apis/implementations/AlertApi/AlertApiForwarder.ts
@@ -13,9 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { AlertApi, AlertMessage } from '@backstage/core-plugin-api';
+import { AlertApi, AlertMessage, Observable } from '@backstage/core-plugin-api';
 import { PublishSubject } from '../../../lib/subjects';
-import { Observable } from '../../../types';
 
 /**
  * Base implementation for the AlertApi that simply forwards alerts to consumers.
diff --git a/packages/core-app-api/src/apis/implementations/AppThemeApi/AppThemeSelector.ts b/packages/core-app-api/src/apis/implementations/AppThemeApi/AppThemeSelector.ts
index 6d7adbb03a..3bd4d764ea 100644
--- a/packages/core-app-api/src/apis/implementations/AppThemeApi/AppThemeSelector.ts
+++ b/packages/core-app-api/src/apis/implementations/AppThemeApi/AppThemeSelector.ts
@@ -14,9 +14,8 @@
  * limitations under the License.
  */
 
-import { AppThemeApi, AppTheme } from '@backstage/core-plugin-api';
+import { AppThemeApi, AppTheme, Observable } from '@backstage/core-plugin-api';
 import { BehaviorSubject } from '../../../lib/subjects';
-import { Observable } from '../../../types';
 
 const STORAGE_KEY = 'theme';
 
diff --git a/packages/core-app-api/src/apis/implementations/ErrorApi/ErrorApiForwarder.ts b/packages/core-app-api/src/apis/implementations/ErrorApi/ErrorApiForwarder.ts
index 479fcdf92d..875d07c0a3 100644
--- a/packages/core-app-api/src/apis/implementations/ErrorApi/ErrorApiForwarder.ts
+++ b/packages/core-app-api/src/apis/implementations/ErrorApi/ErrorApiForwarder.ts
@@ -13,9 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { ErrorApi, ErrorContext } from '@backstage/core-plugin-api';
+import { ErrorApi, ErrorContext, Observable } from '@backstage/core-plugin-api';
 import { PublishSubject } from '../../../lib/subjects';
-import { Observable } from '../../../types';
 
 /**
  * Base implementation for the ErrorApi that simply forwards errors to consumers.
diff --git a/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthPendingRequests.ts b/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthPendingRequests.ts
index f0710cb466..370ba9a3a1 100644
--- a/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthPendingRequests.ts
+++ b/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthPendingRequests.ts
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
+import { Observable } from '@backstage/core-plugin-api';
 import { BehaviorSubject } from '../../../lib/subjects';
-import { Observable } from '../../../types';
 
 type RequestQueueEntry<ResultType> = {
   scopes: Set<string>;
diff --git a/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthRequestManager.ts b/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthRequestManager.ts
index 7a69e82aab..e50c18d271 100644
--- a/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthRequestManager.ts
+++ b/packages/core-app-api/src/apis/implementations/OAuthRequestApi/OAuthRequestManager.ts
@@ -19,10 +19,10 @@ import {
   PendingAuthRequest,
   AuthRequester,
   AuthRequesterOptions,
+  Observable,
 } from '@backstage/core-plugin-api';
 import { OAuthPendingRequests, PendingRequest } from './OAuthPendingRequests';
 import { BehaviorSubject } from '../../../lib/subjects';
-import { Observable } from '../../../types';
 
 /**
  * The OAuthRequestManager is an implementation of the OAuthRequestApi.
diff --git a/packages/core-app-api/src/apis/implementations/StorageApi/WebStorage.ts b/packages/core-app-api/src/apis/implementations/StorageApi/WebStorage.ts
index 225bf0ea5e..3f49b644f6 100644
--- a/packages/core-app-api/src/apis/implementations/StorageApi/WebStorage.ts
+++ b/packages/core-app-api/src/apis/implementations/StorageApi/WebStorage.ts
@@ -17,8 +17,8 @@ import {
   StorageApi,
   StorageValueChange,
   ErrorApi,
+  Observable,
 } from '@backstage/core-plugin-api';
-import { Observable } from '../../../types';
 import ObservableImpl from 'zen-observable';
 
 const buckets = new Map<string, WebStorage>();
diff --git a/packages/core-app-api/src/apis/implementations/auth/github/GithubAuth.ts b/packages/core-app-api/src/apis/implementations/auth/github/GithubAuth.ts
index 040fccf0e1..2ab0e5390f 100644
--- a/packages/core-app-api/src/apis/implementations/auth/github/GithubAuth.ts
+++ b/packages/core-app-api/src/apis/implementations/auth/github/GithubAuth.ts
@@ -24,13 +24,13 @@ import {
   ProfileInfo,
   BackstageIdentity,
   AuthRequestOptions,
+  Observable,
 } from '@backstage/core-plugin-api';
 import { SessionManager } from '../../../../lib/AuthSessionManager/types';
 import {
   AuthSessionStore,
   StaticAuthSessionManager,
 } from '../../../../lib/AuthSessionManager';
-import { Observable } from '../../../../types';
 import { OAuthApiCreateOptions } from '../types';
 
 export type GithubAuthResponse = {
diff --git a/packages/core-app-api/src/apis/implementations/auth/oauth2/OAuth2.ts b/packages/core-app-api/src/apis/implementations/auth/oauth2/OAuth2.ts
index a63636b6f1..c6c251a4f5 100644
--- a/packages/core-app-api/src/apis/implementations/auth/oauth2/OAuth2.ts
+++ b/packages/core-app-api/src/apis/implementations/auth/oauth2/OAuth2.ts
@@ -18,7 +18,6 @@ import OAuth2Icon from '@material-ui/icons/AcUnit';
 import { DefaultAuthConnector } from '../../../../lib/AuthConnector';
 import { RefreshingAuthSessionManager } from '../../../../lib/AuthSessionManager';
 import { SessionManager } from '../../../../lib/AuthSessionManager/types';
-import { Observable } from '../../../../types';
 import {
   AuthRequestOptions,
   BackstageIdentity,
@@ -29,6 +28,7 @@ import {
   SessionState,
   SessionApi,
   BackstageIdentityApi,
+  Observable,
 } from '@backstage/core-plugin-api';
 import { OAuth2Session } from './types';
 import { OAuthApiCreateOptions } from '../types';
diff --git a/packages/core-app-api/src/apis/implementations/auth/saml/SamlAuth.ts b/packages/core-app-api/src/apis/implementations/auth/saml/SamlAuth.ts
index 4bb887eb80..7f747d6977 100644
--- a/packages/core-app-api/src/apis/implementations/auth/saml/SamlAuth.ts
+++ b/packages/core-app-api/src/apis/implementations/auth/saml/SamlAuth.ts
@@ -17,7 +17,6 @@
 import SamlIcon from '@material-ui/icons/AcUnit';
 import { DirectAuthConnector } from '../../../../lib/AuthConnector';
 import { SessionManager } from '../../../../lib/AuthSessionManager/types';
-import { Observable } from '../../../../types';
 import {
   ProfileInfo,
   BackstageIdentity,
@@ -26,6 +25,7 @@ import {
   ProfileInfoApi,
   BackstageIdentityApi,
   SessionApi,
+  Observable,
 } from '@backstage/core-plugin-api';
 import { SamlSession } from './types';
 import {
diff --git a/packages/core-app-api/src/index.ts b/packages/core-app-api/src/index.ts
index 23e31f6a2c..816e788a2b 100644
--- a/packages/core-app-api/src/index.ts
+++ b/packages/core-app-api/src/index.ts
@@ -17,4 +17,3 @@
 export * from './apis';
 export * from './app';
 export * from './routing';
-export * from './types';
diff --git a/packages/core-app-api/src/lib/AuthSessionManager/SessionStateTracker.ts b/packages/core-app-api/src/lib/AuthSessionManager/SessionStateTracker.ts
index 62cdff44ce..72ca789cc9 100644
--- a/packages/core-app-api/src/lib/AuthSessionManager/SessionStateTracker.ts
+++ b/packages/core-app-api/src/lib/AuthSessionManager/SessionStateTracker.ts
@@ -15,8 +15,7 @@
  */
 
 import { BehaviorSubject } from '../subjects';
-import { SessionState } from '@backstage/core-plugin-api';
-import { Observable } from '../../types';
+import { Observable, SessionState } from '@backstage/core-plugin-api';
 
 export class SessionStateTracker {
   private readonly subject = new BehaviorSubject<SessionState>(
diff --git a/packages/core-app-api/src/lib/AuthSessionManager/types.ts b/packages/core-app-api/src/lib/AuthSessionManager/types.ts
index 7b6e5920df..0bed895fba 100644
--- a/packages/core-app-api/src/lib/AuthSessionManager/types.ts
+++ b/packages/core-app-api/src/lib/AuthSessionManager/types.ts
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-import { Observable } from '../../types';
-import { SessionState } from '@backstage/core-plugin-api';
+import { Observable, SessionState } from '@backstage/core-plugin-api';
 
 export type GetSessionOptions = {
   optional?: boolean;
diff --git a/packages/core-app-api/src/lib/subjects.ts b/packages/core-app-api/src/lib/subjects.ts
index 5239e460af..52870538f0 100644
--- a/packages/core-app-api/src/lib/subjects.ts
+++ b/packages/core-app-api/src/lib/subjects.ts
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { Observable } from '../types';
+import { Observable } from '@backstage/core-plugin-api';
 import ObservableImpl from 'zen-observable';
 
 // TODO(Rugvip): These are stopgap and probably incomplete implementations of subjects.
diff --git a/packages/core-app-api/src/types.ts b/packages/core-app-api/src/types.ts
deleted file mode 100644
index ab0aa56a1b..0000000000
--- a/packages/core-app-api/src/types.ts
+++ /dev/null
@@ -1,73 +0,0 @@
-/*
- * Copyright 2020 Spotify AB
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/**
- * This file contains non-react related core types used throughout Backstage.
- */
-
-/**
- * Observer interface for consuming an Observer, see TC39.
- */
-export type Observer<T> = {
-  next?(value: T): void;
-  error?(error: Error): void;
-  complete?(): void;
-};
-
-/**
- * Subscription returned when subscribing to an Observable, see TC39.
- */
-export type Subscription = {
-  /**
-   * Cancels the subscription
-   */
-  unsubscribe(): void;
-
-  /**
-   * Value indicating whether the subscription is closed.
-   */
-  readonly closed: boolean;
-};
-
-// Declares the global well-known Symbol.observable
-// We get the actual runtime polyfill from zen-observable
-declare global {
-  interface SymbolConstructor {
-    readonly observable: symbol;
-  }
-}
-
-/**
- * Observable sequence of values and errors, see TC39.
- *
- * https://github.com/tc39/proposal-observable
- *
- * This is used as a common return type for observable values and can be created
- * using many different observable implementations, such as zen-observable or RxJS 5.
- */
-export type Observable<T> = {
-  [Symbol.observable](): Observable<T>;
-
-  /**
-   * Subscribes to this observable to start receiving new values.
-   */
-  subscribe(observer: Observer<T>): Subscription;
-  subscribe(
-    onNext?: (value: T) => void,
-    onError?: (error: Error) => void,
-    onComplete?: () => void,
-  ): Subscription;
-};
diff --git a/packages/core-plugin-api/src/types.ts b/packages/core-plugin-api/src/types.ts
index 13a8a72570..ab0aa56a1b 100644
--- a/packages/core-plugin-api/src/types.ts
+++ b/packages/core-plugin-api/src/types.ts
@@ -39,9 +39,17 @@ export type Subscription = {
   /**
    * Value indicating whether the subscription is closed.
    */
-  readonly closed: Boolean;
+  readonly closed: boolean;
 };
 
+// Declares the global well-known Symbol.observable
+// We get the actual runtime polyfill from zen-observable
+declare global {
+  interface SymbolConstructor {
+    readonly observable: symbol;
+  }
+}
+
 /**
  * Observable sequence of values and errors, see TC39.
  *
@@ -51,12 +59,14 @@ export type Subscription = {
  * using many different observable implementations, such as zen-observable or RxJS 5.
  */
 export type Observable<T> = {
+  [Symbol.observable](): Observable<T>;
+
   /**
    * Subscribes to this observable to start receiving new values.
    */
   subscribe(observer: Observer<T>): Subscription;
   subscribe(
-    onNext: (value: T) => void,
+    onNext?: (value: T) => void,
     onError?: (error: Error) => void,
     onComplete?: () => void,
   ): Subscription;