Modernize a Classic SharePoint Site Safely: Practical Workflow for Business Users

If you manage a classic SharePoint site that still uses the old team site template or publishing infrastructure, you may see warnings about modernization. Classic sites lack modern team site features like the quick launch, modern document libraries, and Microsoft 365 group connectivity. This article explains a safe, step-by-step workflow to modernize a classic SharePoint site without breaking permissions, content, or customizations. You will learn how to prepare, test, and apply modernization in a controlled way.

What Modernization Does to a Classic SharePoint Site

Modernizing a classic SharePoint site converts the user interface from the old 2010 or 2013 experience to the modern SharePoint experience. This change affects only the visual layout and navigation. The underlying content — documents, lists, pages, permissions, and site features — remains unchanged. Modernization does not delete any data or break existing permission inheritance unless you manually change those settings afterward.

The key technical difference is that a modernized site gains a new home page layout, a simplified navigation bar, and improved compatibility with modern web parts. The site is not moved to a new URL. All existing links to documents and pages continue to work. The site collection ID remains the same, so no DNS or URL changes are required.

What Modernization Does Not Do

Modernization does not automatically connect the site to a Microsoft 365 group. It does not change the site owner. It also does not remove custom master pages or custom CSS. If your site has heavy customizations, you may need to clean those up separately before or after the modernization process.

How to Modernize a Classic SharePoint Site Safely

The following workflow uses the SharePoint admin center and SharePoint Online Management Shell. You need SharePoint admin permissions to run these steps. Perform each step in the order listed. Do not skip the health check.

Step 1: Run the Site Health Check

1. Open the classic site settings
   Go to the classic SharePoint site. Click the gear icon in the upper right and select Site settings.
2. Navigate to the upgrade section
   Under the Site Collection Administration section, click Site collection upgrade. If you do not see this option, the site may already be modern or you lack permissions.
3. Click Check for issues
   On the Site collection upgrade page, click Check for issues. SharePoint scans the site for known compatibility problems. Wait for the report to finish. Review any warnings. Common warnings include custom master pages, old web part zones, and unsupported sandbox solutions.
4. Resolve critical issues
   If the report shows red errors, fix those before proceeding. For example, if a custom master page is flagged, either remove it or update it to a compatible version. You can find the master page in Site settings > Master page.

Step 2: Back Up the Site

1. Export the site template
   Go to Site settings > Save site as template. This creates a .wsp file that contains the site structure, content types, and list definitions. This is not a full content backup. It is a fallback for the site structure.
2. Back up content manually if needed
   If the site contains critical documents, download a copy to a local folder or use the SharePoint Admin Center to export the site to a .csv file. The export tool is under Admin centers > SharePoint > More features > Content migration.

Step 3: Connect to SharePoint Online Management Shell

1. Install the module if not already installed
   Open Windows PowerShell as an administrator. Run Install-Module -Name Microsoft.Online.SharePoint.PowerShell. Confirm the installation.
2. Connect to SharePoint Online
   Run Connect-SPOService -Url https://yourtenant-admin.sharepoint.com. Replace yourtenant with your actual tenant name. Sign in with an account that has SharePoint admin permissions.

Step 4: Request the Modernization

1. Run the Request-SPOSiteUpgrade command
   In the PowerShell window, run Request-SPOSiteUpgrade -Identity https://yourtenant.sharepoint.com/sites/classicsite. Replace the URL with the actual URL of the classic site. This command queues the modernization job.
2. Wait for the job to complete
   The command returns immediately. The actual modernization runs in the background. Check the status by running Get-SPOSite -Identity https://yourtenant.sharepoint.com/sites/classicsite | fl Status. Look for the Status property. It changes from Active to Upgrading and then back to Active. This can take from a few minutes to an hour depending on site size.

Step 5: Verify the Modernization

1. Open the site in a browser
   Navigate to the site URL. The home page now shows the modern layout. The left navigation bar is replaced with a top navigation bar. The site title appears at the top.
2. Check the site status in the admin center
   Go to the SharePoint admin center > Active sites. Find the site. Under Site status, confirm it shows Active and the Template column shows a modern template like STS#3 for a team site.
3. Test key pages and libraries
   Click through a few document libraries, lists, and pages. Verify that all content displays correctly. Check that custom web parts that were on classic pages still work. If they do not, you may need to recreate them using modern web parts.

Common Issues After Modernization and How to Handle Them

Custom Master Page Breaks the Modern Layout

If your classic site used a custom master page, the modern layout may not apply correctly. The site might still show the classic UI. To fix this, go to Site settings > Master page and switch the master page back to the default seattle.master for classic or remove the custom master page entirely. Then run the modernization request again.

Modernization Request Fails with an Error

If the PowerShell command returns an error like Cannot upgrade site because it has unsupported features, check the site health report again. Common unsupported features include sandbox solutions, old wiki pages, and custom themes. Remove or update those features before retrying the request.

Site Navigation Does Not Work as Expected

After modernization, the top navigation bar may not show all links that were in the classic left navigation. You need to manually configure the modern navigation. Go to Site settings > Navigation and choose Structural navigation or Managed navigation. Then edit the top navigation links to match the old structure.

Classic Site vs Modern Site: Key Differences After Modernization

Item	Classic Site	Modern Site
Home page layout	Wiki page with web part zones	Modern page with sections and web parts
Navigation	Left-side quick launch	Top horizontal navigation bar
Document library display	Classic view with ribbon	Modern view with file cards and preview
Compatibility with Microsoft 365 groups	Not connected	Not automatically connected — requires group connection separately
Custom master pages	Supported	Ignored — modern layout uses its own framework
Sandbox solutions	Supported	Not supported — must be removed before modernization

The modernization process does not change the site template in the database. It only changes the rendering engine. You can revert to the classic experience temporarily by clicking the Switch to classic link at the bottom of any modern page. This link is available only for a limited time after modernization. After 30 days, the option disappears.

If you need to revert permanently, you can use the SharePoint admin center to restore the site from a backup or use a site template that was saved before modernization. However, reverting is not recommended unless the site has critical issues that cannot be resolved in the modern UI.

After you confirm the modernized site works correctly, consider connecting it to a Microsoft 365 group if the site is used for team collaboration. This enables features like a shared mailbox, a shared calendar, and Microsoft Teams integration. To connect the site to a group, go to Site settings > Site permissions > Connect to a new Microsoft 365 group. Follow the wizard to complete the connection.