Microsoft has partnered with leading companies to build add-ins that help you get things done right from your inbox. Add-ins in Outlook on the web are programs or utilities that help you automate tasks when you view or create messages.
How do add-ins work?
Installed add-ins are turned on by default, but you'll be prompted to give consent the first time you run them if they need access your data. Even after you add and give consent for an add-in, it can only run when you select it. Most add-ins have access only to the data in the email message that you're working in.
When you install an add-in in Outlook on the web, it will appear in other versions of Outlook as well. For example, if you install an add-in in Outlook on the web, you will see the add-in when you open Outlook 2016.
All add-ins are validated by Microsoft, including those that you install from the Office Store. For more information, see the privacy statement and the terms and conditions section in the add-in’s consent form.
Here's an example of an add-in. The message includes a date and time that triggers the Suggested Meetings add-in, which is installed by default. Selecting the text that includes the date and time opens the Suggested Meetings add-in, but won't take you away from the message. From there, you can select Schedule event to add the event as-is to your calendar or select Edit details to modify the event before adding it to your calendar.

How do I add add-ins?
Note: If the instructions don't match what you see, you might be using an older version of Outlook on the web. Try the Instructions for classic Outlook on the web.
Outlook add-ins can be installed from the in-app Microsoft 365 store or from an XML file.
Add add-ins while reading a message
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In Outlook on the web, select a message.
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From the message's action bar, select Apps > Add apps.
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On the Apps page, search for an add-in by entering the name in the search box or by exploring the add-ins listed in the Featured section.
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Select the add-in of your choice, then choose Add to install the add-in.
Add add-ins while composing a message
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In Outlook on the web, create a new message or reply to an existing message.
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From the ribbon, select Message > Apps > Add apps.
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On the Apps page, search for an add-in by entering the name in the search box or by exploring the add-ins listed in the Featured section.
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Select the add-in of your choice, then choose Add to install the add-in.
Add custom add-ins from a file
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In your preferred browser, go to https://aka.ms/olksideload to open the Add-Ins for Outlook dialog.
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Select My add-ins.
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In the Custom Addins section, select Add a custom add-in, then choose Add from file.
Note: The Add from URL option is no longer available to install a custom Outlook add-in. As a workaround, open the URL in your preferred browser to download the add-in file, then use the Add from File option to install it.
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Select the file for the add-in.
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Select Open to install the add-in.
Instructions for classic Outlook on the web
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Select
Settings > Manage add-ins.
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For free add-ins, use the toggle controls to turn them on or off. For paid add-ins and free trials, select Get it to finish your purchase.
You can also install more add-ins from the Office Store.
If you see a message that you already own an add-in, see You already own this add-in for Outlook.
Add-ins deployed by admins
If you are part of an organization and a new add-in is installed for you by your IT admin, the add-in will be available on the surface where they are designed to work.
Example while composing a message

Example while composing an appointment

Frequently asked questions
Platform |
Requirements |
Outlook 2013 or Outlook 2016 for Windows |
Exchange 2013 SP1+, Exchange Online, or an Outlook account |
Outlook 2016 for Mac |
Exchange 2013 SP1+, Exchange Online, or an Outlook account |
Outlook for iOS or Outlook for Android |
Exchange Online or an Outlook account |
Web browser |
Exchange Online or an Outlook account |
Outlook detects if add-in requested keywords or entities, such as meeting suggestions or addresses, are in your message, and it underlines them. Please note that Microsoft always safeguards your privacy and doesn't attempt to read or comprehend your message. Even though you might see underlined text, no information is sent to the add-in.
Remember, the add-in can run only after you have given your consent to activate it and you selected the underlined text.
An add-in might send data to its own service, but only to complete the task you've requested. For example, the Bing maps add-in might send information to the Bing online service in order to find the location you've requested. All add-ins are required to comply by their privacy policies and Microsoft standards. See the add-in's privacy statement for more details.
Go to the Office Store, and search for the add-in you're looking for. Then, select the add-in to find information such as its overview, requirements, ratings, and reviews.