Build your first Outlook add-in

In this article, you'll walk through the process of building an Outlook task pane add-in that displays at least one property of a selected message.

Create the add-in

You can create an Office Add-in by using the Yeoman generator for Office Add-ins or Visual Studio. The Yeoman generator creates a Node.js project that can be managed with Visual Studio Code or any other editor, whereas Visual Studio creates a Visual Studio solution. Select the tab for the one you'd like to use and then follow the instructions to create your add-in and test it locally.

Prerequisites

  • Node.js (the latest LTS version). Visit the Node.js site to download and install the right version for your operating system.

  • The latest version of Yeoman and the Yeoman generator for Office Add-ins. To install these tools globally, run the following command via the command prompt.

    npm install -g yo generator-office
    

    Note

    Even if you've previously installed the Yeoman generator, we recommend you update your package to the latest version from npm.

  • Office connected to a Microsoft 365 subscription (including Office on the web).

    Note

    If you don't already have Office, you might qualify for a Microsoft 365 E5 developer subscription through the Microsoft 365 Developer Program; for details, see the FAQ. Alternatively, you can sign up for a 1-month free trial or purchase a Microsoft 365 plan.

  • Outlook 2016 or later on Windows (connected to a Microsoft 365 account), Outlook on Mac, or Outlook on the web.

Create the add-in project

  1. Run the following command to create an add-in project using the Yeoman generator. A folder that contains the project will be added to the current directory.

    yo office
    

    Note

    When you run the yo office command, you may receive prompts about the data collection policies of Yeoman and the Office Add-in CLI tools. Use the information that's provided to respond to the prompts as you see fit.

    When prompted, provide the following information to create your add-in project.

    • Choose a project type - Office Add-in Task Pane project

    • Choose a script type - JavaScript

    • What do you want to name your add-in? - My Office Add-in

    • Which Office client application would you like to support? - Outlook

    The prompts and answers for the Yeoman generator in a command line interface.

    After you complete the wizard, the generator will create the project and install supporting Node components.

    Note

    If you're using Node.js version 20.0.0 or later, you may see a warning when the generator runs the installation that you have an unsupported engine. We're working on a fix for this. In the meantime, the warning doesn't affect the generator or the project you generate, so it can be ignored.

    Tip

    You can ignore the next steps guidance that the Yeoman generator provides after the add-in project's been created. The step-by-step instructions within this article provide all of the guidance you'll need to complete this tutorial.

  2. Navigate to the root folder of the web application project.

    cd "My Office Add-in"
    

Explore the project

The add-in project that you've created with the Yeoman generator contains sample code for a very basic task pane add-in.

  • The ./manifest.xml file in the root directory of the project defines the settings and capabilities of the add-in.
  • The ./src/taskpane/taskpane.html file contains the HTML markup for the task pane.
  • The ./src/taskpane/taskpane.css file contains the CSS that's applied to content in the task pane.
  • The ./src/taskpane/taskpane.js file contains the Office JavaScript API code that facilitates interaction between the task pane and Outlook.

Update the code

  1. Open your project in VS Code or your preferred code editor.

    Tip

    On Windows, you can navigate to the root directory of the project via the command line and then enter code . to open that folder in VS Code. On Mac, you'll need to add the code command to the path before you can use that command to open the project folder in VS Code.

  2. Open the file ./src/taskpane/taskpane.html and replace the entire <main> element (within the <body> element) with the following markup. This new markup adds a label where the script in ./src/taskpane/taskpane.js will write data.

    <main id="app-body" class="ms-welcome__main" style="display: none;">
        <h2 class="ms-font-xl"> Discover what Office Add-ins can do for you today! </h2>
        <p><label id="item-subject"></label></p>
        <div role="button" id="run" class="ms-welcome__action ms-Button ms-Button--hero ms-font-xl">
            <span class="ms-Button-label">Run</span>
        </div>
    </main>
    
  3. In your code editor, open the file ./src/taskpane/taskpane.js, then add the following code to the run function. This code uses the Office JavaScript API to get a reference to the current message and write its subject property value to the task pane.

    // Get a reference to the current message
    const item = Office.context.mailbox.item;
    
    // Write message property value to the task pane
    document.getElementById("item-subject").innerHTML = "<b>Subject:</b> <br/>" + item.subject;
    

    Your taskpane.js file should now contain the following code.

    /*
     * Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
     * See LICENSE in the project root for license information.
     */
    
    /* global document, Office */
    
    Office.onReady((info) => {
      if (info.host === Office.HostType.Outlook) {
        document.getElementById("sideload-msg").style.display = "none";
        document.getElementById("app-body").style.display = "flex";
        document.getElementById("run").onclick = run;
      }
    });
    
    export async function run() {
      // Get a reference to the current message
      const item = Office.context.mailbox.item;
    
      // Write message property value to the task pane
      document.getElementById("item-subject").innerHTML = "<b>Subject:</b> <br/>" + item.subject;
    }
    

Try it out

Note

Office Add-ins should use HTTPS, not HTTP, even while you're developing. If you're prompted to install a certificate after you run one of the following commands, accept the prompt to install the certificate that the Yeoman generator provides. You may also have to run your command prompt or terminal as an administrator for the changes to be made.

  1. Run the following command in the root directory of your project. When you run this command, the local web server starts and your add-in will be sideloaded.

    npm start
    
  2. In Outlook, view a message in the Reading Pane, or open the message in its own window.

  3. Choose the Home tab (or the Message tab if you opened the message in a new window), and then choose the Show Taskpane button on the ribbon to open the add-in task pane.

    A message window in Outlook with the add-in ribbon button highlighted.

  4. When prompted with the WebView Stop On Load dialog box, select OK.

    Note

    If you select Cancel, the dialog won't be shown again while this instance of the add-in is running. However, if you restart your add-in, you'll see the dialog again.

  5. Scroll to the bottom of the task pane and choose the Run link to write the message subject to the task pane.

    The add-in's task pane with the Run link highlighted.

    The add-in's task pane displaying message subject.

Next steps

Congratulations, you've successfully created your first Outlook task pane add-in! Next, learn more about the capabilities of an Outlook add-in and build a more complex add-in by following along with the Outlook add-in tutorial.

Troubleshooting

Ensure your environment is ready for Office development by following the instructions in Set up your development environment.

The automatic npm install step Yo Office performs may fail. If you see errors when trying to run npm start, navigate to the newly created project folder in a command prompt and manually run npm install. For more information about Yo Office, see Create Office Add-in projects using the Yeoman Generator.

Some of the sample code uses ES6 JavaScript. This isn't compatible with older versions of Office that use the Trident (Internet Explorer 11) browser engine. For information on how to support those platforms in your add-in, see Support older Microsoft webviews and Office versions. If you don't already have a Microsoft 365 subscription to use for development, you might qualify for a Microsoft 365 E5 developer subscription through the Microsoft 365 Developer Program; for details, see the FAQ. Alternatively, you can sign up for a 1-month free trial or purchase a Microsoft 365 plan.

If you receive the error "We can't open this add-in from localhost" in the task pane, follow the steps outlined in the troubleshooting article.

Code samples

See also