diff --git a/package.json b/package.json
index 6b757c3..eb9eb61 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "notificationapi-node-server-sdk",
-  "version": "0.17.2",
+  "version": "0.18.0",
   "description": "NotificationAPI server-side library for Node.js",
   "keywords": [
     "notificationapi",
diff --git a/src/__tests__/index.test.ts b/src/__tests__/index.test.ts
index e11f23c..cfe9db0 100644
--- a/src/__tests__/index.test.ts
+++ b/src/__tests__/index.test.ts
@@ -7,10 +7,12 @@ import {
   Channels,
   CreateSubNotificationRequest,
   DeleteSubNotificationRequest,
+  PushProviders,
   SendRequest,
   SetUserPreferencesRequest,
   User
 } from '../interfaces';
+import { createHmac } from 'crypto';
 
 const axiosMock = new MockAdapter(axios);
 const restoreConsole = mockConsole();
@@ -502,3 +504,57 @@ describe('setUserPreferences with subNotificationId', () => {
     );
   });
 });
+describe('Identify user', () => {
+  const userEndPointRegex = /.*\/users\/.*/;
+  const clientId = 'testClientId_identify_user';
+  const clientSecret = 'testClientSecret_identify_user';
+  const userId = 'testUserId_identify_user';
+  const user: User = {
+    id: userId,
+    email: 'test+node_server_sdk@notificationapi.com',
+    number: '+15005550006',
+    pushTokens: [
+      {
+        type: PushProviders.FCM,
+        token: 'samplePushToken',
+        device: {
+          app_id: 'sample_app_id',
+          ad_id: 'sample_ad_id',
+          device_id: 'sample_device_id',
+          platform: 'sample_platform',
+          manufacturer: 'sample_manufacturer',
+          model: 'sample_model'
+        }
+      }
+    ],
+    webPushTokens: [
+      {
+        sub: {
+          endpoint: 'sample_endpoint',
+          keys: {
+            p256dh: 'sample_p256dh',
+            auth: 'sample_auth'
+          }
+        }
+      }
+    ]
+  };
+  test('makes API calls with a correct request body', async () => {
+    axiosMock.onPost(userEndPointRegex).reply(200);
+    await notificationapi.init(clientId, clientSecret);
+    await notificationapi.identifyUser(user);
+    const { id, ...userData } = user;
+    expect(axiosMock.history.post).toHaveLength(1);
+    expect(axiosMock.history.post[0].data).toEqual(JSON.stringify(userData));
+    expect(axiosMock.history.post[0].url).toEqual(
+      `https://api.notificationapi.com/${clientId}/users/${id}`
+    );
+    expect(axiosMock.history.post[0].headers.Authorization).toEqual(
+      `Basic ${Buffer.from(
+        `${clientId}:${userId}:${createHmac('sha256', clientSecret)
+          .update(`${userId}`)
+          .digest('base64')}`
+      ).toString('base64')}`
+    );
+  });
+});
diff --git a/src/index.ts b/src/index.ts
index e620d22..254efc6 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -4,9 +4,11 @@ import {
   InitConfiguration,
   RetractRequest,
   SendRequest,
-  SetUserPreferencesRequest
+  SetUserPreferencesRequest,
+  User
 } from './interfaces';
 import axios, { AxiosResponse, Method } from 'axios';
+import { createHmac } from 'crypto';
 
 const DEFAULT_BASE_URL = 'https://api.notificationapi.com';
 
@@ -37,6 +39,24 @@ class NotificationAPI {
     this.clientId = clientId;
     this.clientSecret = clientSecret;
   };
+  /** used to identify your user */
+  identifyUser = async (user: User): Promise<AxiosResponse> => {
+    const { id, ...userData } = user;
+    const hashedUserId = `${createHmac('sha256', this.clientSecret as string)
+      .update(id)
+      .digest('base64')}`;
+
+    const customAuthorization =
+      'Basic ' +
+      Buffer.from(`${this.clientId}:${id}:${hashedUserId}`).toString('base64');
+
+    return this.request(
+      'POST',
+      `users/${encodeURIComponent(id)}`,
+      userData,
+      customAuthorization
+    );
+  };
   /** Used to send a notification to the specified user. */
   send = async (sendRequest: SendRequest): Promise<AxiosResponse> => {
     return this.request('POST', 'sender', sendRequest);
@@ -77,19 +97,20 @@ class NotificationAPI {
   request = async (
     method: Method,
     uri: string,
-    data?: unknown
+    data?: unknown,
+    customAuthorization?: string
   ): Promise<AxiosResponse> => {
+    const authorization: string =
+      customAuthorization ??
+      'Basic ' +
+        Buffer.from(`${this.clientId}:${this.clientSecret}`).toString('base64');
     try {
       const res = await axios.request({
         method,
         url: `${this.baseURL}/${this.clientId}/${uri}`,
         data,
         headers: {
-          Authorization:
-            'Basic ' +
-            Buffer.from(`${this.clientId}:${this.clientSecret}`).toString(
-              'base64'
-            )
+          Authorization: authorization
         }
       });
       if (res.status === 202) {
diff --git a/src/interfaces.ts b/src/interfaces.ts
index d627bd7..f137bd6 100644
--- a/src/interfaces.ts
+++ b/src/interfaces.ts
@@ -5,6 +5,10 @@ export interface User {
   email?: string;
   /** Required for SMS/CALL notifications, otherwise optional. Valid format: +15005550006. Unformatted US/Canada numbers are also accepted, e.g., (415) 555-1212, 415-555-1212, or 4155551212.*/
   number?: string;
+  /**Tokens which are required to send mobile push notifications, a user can have multiple devices and a push token is required for each device*/
+  pushTokens?: PushToken[];
+  /**Tokens which are required to send web push notification, a user can have multiple devices and a web push token is required for each device */
+  webPushTokens?: WebPushToken[];
 }
 
 export interface SendRequest {
@@ -95,3 +99,53 @@ export interface InitConfiguration {
   /** To updated the based url. Optional.*/
   baseURL?: string;
 }
+
+export interface PushToken {
+  /**[apn | fcm] The provider token is to be associated with. */
+  type: PushProviders;
+  /**The full token string. */
+  token: string;
+  /**Information about the device the token is associated with. */
+  device: Device;
+}
+
+export enum PushProviders {
+  /**firebase-fcm token provider */
+  FCM = 'FCM',
+  /**APN token provider */
+  APN = 'APN'
+}
+
+export interface Device {
+  /**Id of the application the token is used for */
+  app_id?: string;
+  /**Id of the advertising identifier */
+  ad_id?: string;
+  /**Id of the device the token is associated with */
+  device_id: string;
+  /**The device platform i.e. android, ios*/
+  platform?: string;
+  /**The device manufacturer */
+  manufacturer?: string;
+  /**The device model */
+  model?: string;
+}
+
+/**
+ * Configuration for a Push Subscription. This can be obtained on the frontend by calling
+ * serviceWorkerRegistration.pushManager.subscribe().
+ * The expected format is the same output as JSON.stringify'ing a PushSubscription in the browser.
+ */
+export interface PushSubscription {
+  /**a string value containing the endpoint associated with the push subscription. */
+  endpoint: string;
+  keys: {
+    /**An Elliptic curve Diffie–Hellman public key on the P-256 curve (that is, the NIST secp256r1 elliptic curve). The resulting key is an uncompressed point in ANSI X9.62 format. */
+    p256dh: string;
+    /**An authentication secret, as described in Message Encryption for Web Push. */
+    auth: string;
+  };
+}
+export interface WebPushToken {
+  sub: PushSubscription;
+}