Enable auto-acceleration in SharePoint
Auto-acceleration is a feature in SharePoint in which you specify the default identity provider endpoint for your organization. When a user accesses a resource, instead of signing in to login.microsoftonline.com, the user is sent directly to the identity provider (IdP). If you configured Integrated Windows Authentication on AD FS and the user's computer is domain-joined, they will have a completely seamless single sign on experience, just like accessing an on-premises resource.
To enable auto-acceleration, you must have a single identity provider (IdP). SharePoint must have a specific site to target when accelerating. Your organization can have multiple domains as long as there is a single IdP endpoint.
To enable auto-acceleration, you need to use Microsoft PowerShell.
If you installed a previous version of the SharePoint Online Management Shell, go to Add or remove programs and uninstall "SharePoint Online Management Shell."
On the Download Center page, select your language and then click the Download button. You'll be asked to choose between downloading a x64 and x86 .msi file. Download the x64 file if you're running the 64-bit version of Windows or the x86 file if you're running the 32-bit version. If you don't know, see Which version of Windows operating system am I running?. After the file downloads, run it and follow the steps in the Setup Wizard.
Connect to SharePoint as a global admin or SharePoint admin in Microsoft 365. To learn how, see Getting started with SharePoint Online Management Shell.
Run the following command to enable auto-acceleration on sites that are not shared externally:
Set-SPOTenant -SignInAccelerationDomain "contoso.com"
If you have configured your IdP to support guests, you can enable auto-acceleration on sites that have external sharing enabled by running:
Set-SPOTenant -EnableGuestSignInAcceleration $true
You must run SignInAccelerationDomain before running this command.
For more information, see Set-SPOTenant.
Frequently asked questions about auto-acceleration
What can I do to make the experience as smooth as possible for my users?
A: You can do two things. First, ensure that your internal and external sites are clearly separated. Second, encourage users to access internal sites first as part of their daily workflow. Perhaps consider creating an internal-only site that serves as a welcome page. You can also modify your Group Policy so that users will be directed to an internal home page whenever they open their browser. After the user has signed in to one site (by using either method), they will not be prompted to sign to other sites.
What do I need to do to take advantage of auto acceleration on externally shared sites?
A: Guests can potentially authenticate in one of three places: Azure Active Directory (if their organization is a "cloud" organization or they use a Microsoft account), the IdP of the user's organization, or your IdP (if you use an on-premises extranet solution). If you want to enable auto-acceleration for externally shared sites, your IdP needs to be capable of supporting these use cases (or at least the ones that you want your guests to use). To support guests in Azure AD, Microsoft account, or other IdPs, your IdP will need to be capable of returning the user to the Azure AD signin screen for authentication.