Integrating with Office Online

You can integrate with Office Online to enable your users to view and edit Excel, PowerPoint, and Word files directly in the browser.

If you deliver a web-based experience that allows your users to store Office files or includes Office files as a key part of your solution, you now have the opportunity to integrate Office Online into your experience. This integration works directly against files stored by you. Your users won’t need a separate storage solution to view and edit Office files.

A screenshot that shows a file viewed in Office Online.

Figure 1 Word file open for editing in Office Online

Viewing Office files

You can make viewing available in two ways:

  • By using the high-fidelity previews in Office Online as an integrated part of your experience. For example, you can use these previews in a light box view of a Word document.
  • By offering to show Office files in a full-page interactive preview. Depending on your solution, this might be useful for file browsing or showing read-only files to users or in cases where users don’t have a license to edit files in Office Online.

Editing Office files

Editing is a core part of Office Online integration. When you integrate with Office Online, your users can edit Excel, PowerPoint, and Word files directly in the browser. In addition, users can edit documents collaboratively with other users using Office Online. Here are the key points to note about editing.

Consumers Business users
Do not need an Office 365 subscription. Do need an Office 365 subscription to edit files, but not to view files.
Do not have to log on to use Office Online. Are prompted to authenticate with an Office 365 or a Microsoft account to edit.

Integration process

Integrating with Office Online is relatively simple. You just need to do some HTML and JavaScript work, and set up a few simple REST endpoints. If you are familiar with existing Office protocols, note that you don’t have to implement the [MS-FSSHTTP]: File Synchronization via SOAP over HTTP Protocol (Cobalt). At a high level, to integrate with Office Online, you:

  • Read XML from Office Online that describes the capabilities of Office Online. This is called WOPI discovery.
  • Implement REST endpoints that Office Online uses to learn about, fetch, and update files. To do this, you implement the server side of the WOPI protocol.
  • Provide an HTML page (or pages) that wrap Office Online. This page is called the Building a host page.

The following figure shows the WOPI protocol workflow.

An image that shows the WOPI workfow.

Figure 2 WOPI protocol workflow

To do this, you will need to ensure that your solution meets a few basic requirements.


Authentication is handled by passing Office Online an access token that you generate. Assign this token a reasonable expiration date. Also, we recommend that tokens be valid for a single user against a single file, to help mitigate the risk of token leaks.

See also

Access token

Conflict resolution

Office Online does support multiuser authoring scenarios if all users are using Office Online. However, you are responsible for managing conflicts that may come from applications other than Office Online, either with some form of file locking, or by using another type of conflict resolution.

File IDs

Ensure that files are represented by a persistent ID. This ID must be URL-safe because it might be passed as part of the URL at different times. Also, the ID must not change when the file is renamed, moved, or edited. This ensures an uninterrupted editing experience for your users.

See also

File ID

File versions

You should have a mechanism by which users can clearly identify file versions through the REST APIs. Because files are cached to improve viewing performance, file versions are extremely helpful. Without them, users can’t easily determine whether they have the latest version of the file.

Desktop application integration

We encourage you to provide a way for users to open files in the Excel, PowerPoint, and Word desktop applications from the browser. Office Online is great for many things, but sometimes your users will want to transition to the desktop applications to access features that aren’t available in Office Online at this time.

Security considerations

Office Online is designed to work for enterprises that have strict security requirements. To make sure your integration is as secure as possible, ensure that:

  • All traffic is SSL encrypted.
  • Initial requests to Office Online are made by using POST, where the access token is in the body of the POST request.

Office Online identity can be established by using a public proof key to decrypt part of the WOPI requests. Also, the Office Online file cache indexes stored file contents by using a SHA256 hash as the cache key. You can pass Office Online the hash value using the SHA256 property in the CheckFileInfo response. If not provided, Office Online will generate a cache key from the file ID and version. To ensure that users can’t force a cache collision and view the wrong file, no user-provided information is used to generate the cache key.

Managing Office 365 subscriptions

Business users require an Office 365 subscription to edit files in Office Online. The simplest way to implement this is to have users sign in with a Microsoft account or other valid identity. This establishes that they have the correct subscription. To limit the number of times a user needs to sign in, Office Online first checks for a cookie.

To provide a better experience for users with Office 365 subscriptions, hosts can optionally implement the PutUserInfo WOPI operation. See Tracking users’ subscription status for more information.


If you’re interested in integrating your solution with Office Online, take a moment to register at Office 365 Cloud Storage Partner Program.