diff --git a/src/common/config.ts b/src/common/config.ts
index ac634f2e7..06a058d6e 100644
--- a/src/common/config.ts
+++ b/src/common/config.ts
@@ -3,6 +3,7 @@ import { readFileSync } from "fs";
 import * as path from "path";
 
 import * as logger from "../logger";
+import { currentProjectId } from "./utilities/utils";
 
 let cache: AppOptions | null = null;
 
@@ -36,15 +37,15 @@ export function firebaseConfig(): AppOptions | null {
     return cache;
   }
 
-  if (process.env.GCLOUD_PROJECT) {
+  const projectId = currentProjectId();
+  if (projectId) {
     logger.warn(
       "Warning, estimating Firebase Config based on GCLOUD_PROJECT. Initializing firebase-admin may fail"
     );
     cache = {
-      databaseURL:
-        process.env.DATABASE_URL || `https://${process.env.GCLOUD_PROJECT}.firebaseio.com`,
-      storageBucket: process.env.STORAGE_BUCKET_URL || `${process.env.GCLOUD_PROJECT}.appspot.com`,
-      projectId: process.env.GCLOUD_PROJECT,
+      databaseURL: process.env.DATABASE_URL || `https://${projectId}.firebaseio.com`,
+      storageBucket: process.env.STORAGE_BUCKET_URL || `${projectId}.appspot.com`,
+      projectId: projectId,
     };
     return cache;
   } else {
diff --git a/src/common/encoding.ts b/src/common/encoding.ts
index 88b40ef3f..581a7cef7 100644
--- a/src/common/encoding.ts
+++ b/src/common/encoding.ts
@@ -20,6 +20,8 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+import { currentProjectId } from "./utilities/utils";
+
 // Copied from firebase-tools/src/gcp/proto
 
 /**
@@ -76,12 +78,13 @@ export function serviceAccountFromShorthand(serviceAccount: string): string | nu
   if (serviceAccount === "default") {
     return null;
   } else if (serviceAccount.endsWith("@")) {
-    if (!process.env.GCLOUD_PROJECT) {
+    const projectId = currentProjectId();
+    if (!projectId) {
       throw new Error(
-        `Unable to determine email for service account '${serviceAccount}' because process.env.GCLOUD_PROJECT is not set.`
+        `Unable to determine email for service account '${serviceAccount}' (process.env.GCLOUD_PROJECT and process.env.GCP_PROJECT missing)`
       );
     }
-    return `${serviceAccount}${process.env.GCLOUD_PROJECT}.iam.gserviceaccount.com`;
+    return `${serviceAccount}${projectId}.iam.gserviceaccount.com`;
   } else if (serviceAccount.includes("@")) {
     return serviceAccount;
   } else {
diff --git a/src/common/providers/database.ts b/src/common/providers/database.ts
index e1da47c7d..7dfcbfad8 100644
--- a/src/common/providers/database.ts
+++ b/src/common/providers/database.ts
@@ -24,6 +24,7 @@ import { App } from "firebase-admin/app";
 import * as database from "firebase-admin/database";
 import { firebaseConfig } from "../../common/config";
 import { joinPath, pathParts } from "../../common/utilities/path";
+import { currentProjectId } from "../utilities/utils";
 
 /**
  * Interface representing a Firebase Realtime database data snapshot.
@@ -60,8 +61,8 @@ export class DataSnapshot implements database.DataSnapshot {
       this.instance = app.options.databaseURL;
     } else if (config.databaseURL) {
       this.instance = config.databaseURL;
-    } else if (process.env.GCLOUD_PROJECT) {
-      this.instance = "https://" + process.env.GCLOUD_PROJECT + "-default-rtdb.firebaseio.com";
+    } else if (currentProjectId()) {
+      this.instance = "https://" + currentProjectId() + "-default-rtdb.firebaseio.com";
     }
 
     this._path = path;
diff --git a/src/common/providers/identity.ts b/src/common/providers/identity.ts
index 9997d7569..2f2ba01dc 100644
--- a/src/common/providers/identity.ts
+++ b/src/common/providers/identity.ts
@@ -26,6 +26,7 @@ import * as logger from "../../logger";
 import { EventContext } from "../../v1/cloud-functions";
 import { getApp } from "../app";
 import { isDebugFeatureEnabled } from "../debug";
+import { currentProjectId } from "../utilities/utils";
 import { HttpsError, unsafeDecodeToken } from "./https";
 
 export { HttpsError };
@@ -784,7 +785,7 @@ export function getUpdateMask(authResponse?: BeforeCreateResponse | BeforeSignIn
 export function wrapHandler(eventType: AuthBlockingEventType, handler: HandlerV1 | HandlerV2) {
   return async (req: express.Request, res: express.Response): Promise<void> => {
     try {
-      const projectId = process.env.GCLOUD_PROJECT;
+      const projectId = currentProjectId();
       if (!isValidRequest(req)) {
         logger.error("Invalid request, unable to process");
         throw new HttpsError("invalid-argument", "Bad Request");
diff --git a/src/common/utilities/utils.ts b/src/common/utilities/utils.ts
index 0bcfc1ad1..3309ac634 100644
--- a/src/common/utilities/utils.ts
+++ b/src/common/utilities/utils.ts
@@ -24,6 +24,24 @@ function isObject(obj: any): boolean {
   return typeof obj === "object" && !!obj;
 }
 
+/**
+ * Retrieves the current GCL project ID from process.env.GCLOUD_PROJECT (which
+ * is guaranteed to be set during firebase deploy) or process.env.PROJECT_ID
+ * (which is guaranteed to be set by the Extensions backend). Use this instead
+ * of directly querying process.env if your code can be used in either context.
+ *  
+ * @internal 
+ */
+export function currentProjectId(assertPresence = false): string {
+  const projectId = process.env.GCLOUD_PROJECT || process.env.PROJECT_ID;
+  if (!projectId && assertPresence) {
+    throw new Error(
+      `Unable to determine current GCP project--neither process.env.GCLOUD_PROJECT nor process.env.GCP_PROJECT are set.`
+    );
+  }
+  return projectId;
+}
+
 /** @hidden */
 export function applyChange(src: any, dest: any) {
   // if not mergeable, don't merge
diff --git a/src/logger/index.ts b/src/logger/index.ts
index e50e5088a..36336aff1 100644
--- a/src/logger/index.ts
+++ b/src/logger/index.ts
@@ -22,6 +22,7 @@
 
 import { format } from "util";
 import { traceContext } from "../common/trace";
+import { currentProjectId } from "../common/utilities/utils";
 
 import { CONSOLE_SEVERITY, UNPATCHED_CONSOLE } from "./common";
 
@@ -156,7 +157,7 @@ function entryFromArgs(severity: LogSeverity, args: any[]): LogEntry {
   }
   return {
     "logging.googleapis.com/trace": ctx?.traceId
-      ? `projects/${process.env.GCLOUD_PROJECT}/traces/${ctx.traceId}`
+      ? `projects/${currentProjectId()}/traces/${ctx.traceId}`
       : undefined,
     ...entry,
     severity,
diff --git a/src/v1/providers/analytics.ts b/src/v1/providers/analytics.ts
index 63895a7ca..e3bfe00ca 100644
--- a/src/v1/providers/analytics.ts
+++ b/src/v1/providers/analytics.ts
@@ -20,6 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+import { currentProjectId } from "../../common/utilities/utils";
 import { CloudFunction, Event, EventContext, makeCloudFunction } from "../cloud-functions";
 import { DeploymentOptions } from "../function-configuration";
 
@@ -43,10 +44,7 @@ export function event(analyticsEventType: string) {
 /** @internal */
 export function _eventWithOptions(analyticsEventType: string, options: DeploymentOptions) {
   return new AnalyticsEventBuilder(() => {
-    if (!process.env.GCLOUD_PROJECT) {
-      throw new Error("process.env.GCLOUD_PROJECT is not set.");
-    }
-    return "projects/" + process.env.GCLOUD_PROJECT + "/events/" + analyticsEventType;
+    return "projects/" + currentProjectId(true) + "/events/" + analyticsEventType;
   }, options);
 }
 
diff --git a/src/v1/providers/auth.ts b/src/v1/providers/auth.ts
index edef7b0bb..92e1dc3d2 100644
--- a/src/v1/providers/auth.ts
+++ b/src/v1/providers/auth.ts
@@ -44,6 +44,7 @@ import {
 } from "../cloud-functions";
 import { DeploymentOptions } from "../function-configuration";
 import { initV1Endpoint } from "../../runtime/manifest";
+import { currentProjectId } from "../../common/utilities/utils";
 
 // TODO: yank in next breaking change release
 export { UserRecord, UserInfo, UserRecordMetadata, userRecordConstructor };
@@ -88,10 +89,7 @@ export function user(userOptions?: UserOptions): UserBuilder {
 export function _userWithOptions(options: DeploymentOptions, userOptions: UserOptions) {
   return new UserBuilder(
     () => {
-      if (!process.env.GCLOUD_PROJECT) {
-        throw new Error("process.env.GCLOUD_PROJECT is not set.");
-      }
-      return "projects/" + process.env.GCLOUD_PROJECT;
+      return "projects/" + currentProjectId(true);
     },
     options,
     userOptions
diff --git a/src/v1/providers/firestore.ts b/src/v1/providers/firestore.ts
index 57ccf4603..7fd1df725 100644
--- a/src/v1/providers/firestore.ts
+++ b/src/v1/providers/firestore.ts
@@ -27,6 +27,7 @@ import { getApp } from "../../common/app";
 import { Change } from "../../common/change";
 import { ParamsOf } from "../../common/params";
 import { dateToTimestampProto } from "../../common/utilities/encoder";
+import { currentProjectId } from "../../common/utilities/utils";
 import * as logger from "../../logger";
 import { CloudFunction, Event, EventContext, makeCloudFunction } from "../cloud-functions";
 import { DeploymentOptions } from "../function-configuration";
@@ -101,15 +102,7 @@ export class NamespaceBuilder {
 
   document<Path extends string>(path: Path) {
     return new DocumentBuilder<Path>(() => {
-      if (!process.env.GCLOUD_PROJECT) {
-        throw new Error("process.env.GCLOUD_PROJECT is not set.");
-      }
-      const database = posix.join(
-        "projects",
-        process.env.GCLOUD_PROJECT,
-        "databases",
-        this.database
-      );
+      const database = posix.join("projects", currentProjectId(true), "databases", this.database);
       return posix.join(
         database,
         this.namespace ? `documents@${this.namespace}` : "documents",
diff --git a/src/v1/providers/pubsub.ts b/src/v1/providers/pubsub.ts
index 57a28803c..709ce9c71 100644
--- a/src/v1/providers/pubsub.ts
+++ b/src/v1/providers/pubsub.ts
@@ -20,6 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+import { currentProjectId } from "../../common/utilities/utils";
 import { CloudFunction, EventContext, makeCloudFunction } from "../cloud-functions";
 import { DeploymentOptions, ScheduleRetryConfig } from "../function-configuration";
 
@@ -46,10 +47,7 @@ export function _topicWithOptions(topic: string, options: DeploymentOptions): To
   }
 
   return new TopicBuilder(() => {
-    if (!process.env.GCLOUD_PROJECT) {
-      throw new Error("process.env.GCLOUD_PROJECT is not set.");
-    }
-    return `projects/${process.env.GCLOUD_PROJECT}/topics/${topic}`;
+    return `projects/${currentProjectId(true)}/topics/${topic}`;
   }, options);
 }
 
@@ -101,11 +99,8 @@ export function _scheduleWithOptions(
   options: DeploymentOptions
 ): ScheduleBuilder {
   const triggerResource = () => {
-    if (!process.env.GCLOUD_PROJECT) {
-      throw new Error("process.env.GCLOUD_PROJECT is not set.");
-    }
     // The CLI will append the correct topic name based on region and function name
-    return `projects/${process.env.GCLOUD_PROJECT}/topics`;
+    return `projects/${currentProjectId(true)}/topics`;
   };
   return new ScheduleBuilder(triggerResource, {
     ...options,
diff --git a/src/v1/providers/remoteConfig.ts b/src/v1/providers/remoteConfig.ts
index cf67383dc..70de8fcfc 100644
--- a/src/v1/providers/remoteConfig.ts
+++ b/src/v1/providers/remoteConfig.ts
@@ -20,6 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+import { currentProjectId } from "../../common/utilities/utils";
 import { CloudFunction, EventContext, makeCloudFunction } from "../cloud-functions";
 import { DeploymentOptions } from "../function-configuration";
 
@@ -49,10 +50,7 @@ export function _onUpdateWithOptions(
   options: DeploymentOptions
 ): CloudFunction<TemplateVersion> {
   const triggerResource = () => {
-    if (!process.env.GCLOUD_PROJECT) {
-      throw new Error("process.env.GCLOUD_PROJECT is not set.");
-    }
-    return `projects/${process.env.GCLOUD_PROJECT}`;
+    return `projects/${currentProjectId(true)}`;
   };
   return new UpdateBuilder(triggerResource, options).onUpdate(handler);
 }
diff --git a/src/v1/providers/testLab.ts b/src/v1/providers/testLab.ts
index d0d0cd06a..49c711326 100644
--- a/src/v1/providers/testLab.ts
+++ b/src/v1/providers/testLab.ts
@@ -20,6 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+import { currentProjectId } from "../../common/utilities/utils";
 import { CloudFunction, Event, EventContext, makeCloudFunction } from "../cloud-functions";
 import { DeploymentOptions } from "../function-configuration";
 
@@ -38,10 +39,7 @@ export function testMatrix() {
 /** @internal */
 export function _testMatrixWithOpts(opts: DeploymentOptions) {
   return new TestMatrixBuilder(() => {
-    if (!process.env.GCLOUD_PROJECT) {
-      throw new Error("process.env.GCLOUD_PROJECT is not set.");
-    }
-    return "projects/" + process.env.GCLOUD_PROJECT + "/testMatrices/{matrix}";
+    return "projects/" + currentProjectId(true) + "/testMatrices/{matrix}";
   }, opts);
 }
 
diff --git a/src/v2/providers/pubsub.ts b/src/v2/providers/pubsub.ts
index 98b966c45..aa4b3191e 100644
--- a/src/v2/providers/pubsub.ts
+++ b/src/v2/providers/pubsub.ts
@@ -33,6 +33,7 @@ import { wrapTraceContext } from "../trace";
 import { Expression } from "../../params";
 import * as options from "../options";
 import { SecretParam } from "../../params/types";
+import { currentProjectId } from "../../common/utilities/utils";
 
 /**
  * Google Cloud Pub/Sub is a globally distributed message bus that automatically scales as you need it.
@@ -323,7 +324,7 @@ export function onMessagePublished<T = any>(
         },
         eventTrigger: {
           eventType: "google.cloud.pubsub.topic.v1.messagePublished",
-          resource: `projects/${process.env.GCLOUD_PROJECT}/topics/${topic}`,
+          resource: `projects/${currentProjectId()}/topics/${topic}`,
         },
       };
     },