Enable file sharing using UI Library and Azure Blob Storage


This feature of Azure Communication Services is currently in preview.

Preview APIs and SDKs are provided without a service-level agreement. We recommend that you don't use them for production workloads. Some features might not be supported, or they might have constrained capabilities.

For more information, review Supplemental Terms of Use for Microsoft Azure Previews.

In this tutorial, we'll be configuring the Azure Communication Services UI Library Chat Composite to enable file sharing. The UI Library Chat Composite provides a set of rich components and UI controls that can be used to enable file sharing. We will be leveraging Azure Blob Storage to enable the storage of the files that are shared through the chat thread.


Azure Communication Services doesn't provide a file storage service. You will need to use your own file storage service for sharing files. For the pupose of this tutorial, we will be using Azure Blob Storage.**

Download code

Access the full code for this tutorial on GitHub. If you want to leverage file sharing using UI Components, reference this sample.


This tutorial assumes that you already know how to setup and run a Chat Composite. You can follow the Chat Composite tutorial to learn how to set up and run a Chat Composite.


The UI Library Chat Composite supports file sharing by enabling developers to pass the URL to a hosted file that is sent through the Azure Communication Services chat service. The UI Library renders the attached file and supports multiple extensions to configure the look and feel of the file sent. More specifically, it supports the following features:

  1. Attach file button for picking files through the OS File Picker
  2. Configure allowed file extensions.
  3. Enable/disable multiple uploads.
  4. File Icons for a wide variety of file types.
  5. File upload/download cards with progress indicators.
  6. Ability to dynamically validate each file upload and display errors on the UI.
  7. Ability to cancel an upload and remove an uploaded file before it is sent.
  8. View uploaded files in MessageThread, download them. Allows asynchronous downloads.

The diagram below shows a typical flow of a file sharing scenario for both upload and download. The section marked as Client Managed shows the building blocks that need to be implemented by developers.

Filesharing typical flow

Setup File Storage using Azure Blob

You can follow the tutorial Upload file to Azure Blob Storage with an Azure Function to write the backend code required for file sharing.

Once implemented, you can call this Azure Function inside the uploadHandler function to upload files to Azure Blob Storage. For the remaining of the tutorial, we will assume you have generated the function using the tutorial for Azure Blob Storage linked above.

Securing your Azure Blob Storage Container

Note that the tutorial above assumes that your Azure blob storage container allows public access to the files you upload. Making your Azure storage containers public isn't recommended for real world production applications.

For downloading the files you upload to Azure blob storage, you can use shared access signatures (SAS). A shared access signature (SAS) provides secure delegated access to resources in your storage account. With a SAS, you have granular control over how a client can access your data.

The downloadable GitHub sample showcases the use of SAS for creating SAS URLs to Azure Storage contents. Additionally, you can read more about SAS.

UI Library requires a React environment to be setup. Next we will do that. If you already have a React App, you can skip this section.

Set Up React App

We'll use the create-react-app template for this quickstart. For more information, see: Get Started with React

npx create-react-app ui-library-quickstart-composites --template typescript

cd ui-library-quickstart-composites

At the end of this process, you should have a full application inside of the folder ui-library-quickstart-composites. For this quickstart, we'll be modifying files inside of the src folder.

Install the Package

Use the npm install command to install the Azure Communication Services UI Library for JavaScript.

npm install @azure/communication-react

@azure/communication-react specifies core Azure Communication Services as peerDependencies so that you can most consistently use the API from the core libraries in your application. You need to install those libraries as well:

npm install @azure/communication-calling@1.4.4
npm install @azure/communication-chat@1.2.0

Run Create React App

Let's test the Create React App installation by running:

npm run start

Configuring Chat Composite to enable File Sharing

You will need to replace the variable values for both common variable required to initialize the chat composite.


import { FileUploadHandler, FileUploadManager } from '@azure/communication-react';
import { initializeFileTypeIcons } from '@fluentui/react-file-type-icons'; 
import {
} from '@azure/communication-react';
import React, { useMemo } from 'react';


function App(): JSX.Element {
  // Common variables
  const endpointUrl = 'INSERT_ENDPOINT_URL';
  const userId = ' INSERT_USER_ID';
  const displayName = 'INSERT_DISPLAY_NAME';
  const token = 'INSERT_ACCESS_TOKEN';
  const threadId = 'INSERT_THREAD_ID';

  // We can't even initialize the Chat and Call adapters without a well-formed token.
  const credential = useMemo(() => {
    try {
      return new AzureCommunicationTokenCredential(token);
    } catch {
      console.error('Failed to construct token credential');
      return undefined;
  }, [token]);

  // Memoize arguments to `useAzureCommunicationChatAdapter` so that
  // a new adapter is only created when an argument changes.
  const chatAdapterArgs = useMemo(
    () => ({
      endpoint: endpointUrl,
      userId: fromFlatCommunicationIdentifier(userId) as CommunicationUserIdentifier,
    [userId, displayName, credential, threadId]
  const chatAdapter = useAzureCommunicationChatAdapter(chatAdapterArgs);

  if (!!chatAdapter) {
    return (
        <div style={containerStyle}>
              fileSharing: {
                uploadHandler: fileUploadHandler,
                // If `fileDownloadHandler` is not provided. The file URL is opened in a new tab.
                downloadHandler: fileDownloadHandler,
                accept: 'image/png, image/jpeg, text/plain, .docx',
                multiple: true
            }} />
  if (credential === undefined) {
    return <h3>Failed to construct credential. Provided token is malformed.</h3>;
  return <h3>Initializing...</h3>;

const fileUploadHandler: FileUploadHandler = async (userId, fileUploads) => {
  for (const fileUpload of fileUploads) {
    try {
      const { name, url, extension } = await uploadFileToAzureBlob(fileUpload);
      fileUpload.notifyUploadCompleted({ name, extension, url });
    } catch (error) {
      if (error instanceof Error) {

const uploadFileToAzureBlob = async (fileUpload: FileUploadManager) => {
  // You need to handle the file upload here and upload it to Azure Blob Storage.
  // Below you can find snippets for how to configure the upload
  // Optionally, you can also update the file upload progress.
  return {
    name: 'SampleFile.jpg', // File name displayed during download
    url: 'https://sample.com/sample.jpg', // Download URL of the file.
    extension: 'jpeg' // File extension used for file icon during download.
const fileDownloadHandler: FileDownloadHandler = async (userId, fileData) => {
      return new URL(fileData.url);

Configure upload method to use Azure Blob Storage

To enable Azure Blob Storage upload, we will modify the uploadFileToAzureBlob method we declared above with the following code. You will need to replace the Azure Function information below to enable to upload.


const uploadFileToAzureBlob = async (fileUpload: FileUploadManager) => {
  const file = fileUpload.file;
  if (!file) {
    throw new Error('fileUpload.file is undefined');

  const filename = file.name;
  const fileExtension = file.name.split('.').pop();

  // Following is an example of calling an Azure Function to handle file upload
  // The https://learn.microsoft.com/azure/developer/javascript/how-to/with-web-app/azure-function-file-upload
  // tutorial uses 'username' parameter to specify the storage container name.
  // Note that the container in the tutorial is private by default. To get default downloads working in
  // this sample, you need to change the container's access level to Public via Azure Portal.
  const username = 'ui-library';
  // You can get function url from the Azure Portal:
  const azFunctionBaseUri='<YOUR_AZURE_FUNCTION_URL>';
  const uri = `${azFunctionBaseUri}&username=${username}&filename=${filename}`;
  const formData = new FormData();
  formData.append(file.name, file);
  const response = await axios.request({
    method: "post",
    url: uri,
    data: formData,
    onUploadProgress: (p) => {
      // Optionally, you can update the file upload progess.
      fileUpload.notifyUploadProgressChanged(p.loaded / p.total);
  const storageBaseUrl = 'https://<YOUR_STORAGE_ACCOUNT>.blob.core.windows.net';

  return {
    name: filename,
    url: `${storageBaseUrl}/${username}/${filename}`,
    extension: fileExtension

Error Handling

When an upload fails, the UI Library Chat Composite will display an error message.

File Upload Error Bar

Here is sample code showcasing how you can fail an upload due to a size validation error by changing the fileUploadHandler above.


import { FileUploadHandler } from from '@azure/communication-react';

const fileUploadHandler: FileUploadHandler = async (userId, fileUploads) => {
  for (const fileUpload of fileUploads) {
    if (fileUpload.file && fileUpload.file.size > 99 * 1024 * 1024) {
      // Notify ChatComposite about upload failure. 
      // Allows you to provide a custom error message.
      fileUpload.notifyUploadFailed('File too big. Select a file under 99 MB.');

File Downloads - Advanced Usage

By default, the file url provided through notifyUploadCompleted method will be used to trigger a file download. However, if you need to handle a download in a different way, you can provide a custom downloadHandler to ChatComposite. Below we will modify the fileDownloadHandler that we declared above to check for an authorized user before allowing to download the file.


import { FileDownloadHandler } from "communication-react";

const isUnauthorizedUser = (userId: string): boolean => {
  // You need to write your own logic here for this example.

const fileDownloadHandler: FileDownloadHandler = async (userId, fileData) => {
  if (isUnauthorizedUser(userId)) {
    // Error message will be displayed to the user.
    return { errorMessage: 'You don’t have permission to download this file.' };
  } else {
    // If this function returns a Promise that resolves a URL string, 
    // the URL is opened in a new tab. 
    return new URL(fileData.url);

Download errors will be displayed to users in an error bar on top of the Chat Composite.

File Download Error

Clean up resources

If you want to clean up and remove a Communication Services subscription, you can delete the resource or resource group. Deleting the resource group also deletes any other resources associated with it. You can find out more about cleaning up Azure Communication Service resources and cleaning Azure Function Resources.

Next steps

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