This chapter covers SharePoint Modern sites versus Classic sites, a key topic in the MS-900 exam domain 'M365 Productivity' (Objective 2.3: Describe the capabilities of Microsoft 365 productivity solutions). Understanding the differences between these two site architectures is critical because Microsoft is deprecating Classic features and pushing adoption of Modern sites. Expect 3-5 exam questions on this topic, focusing on feature comparisons, migration benefits, and which site type to use in given scenarios.
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Think of a Classic SharePoint site as a house built in the 1990s. It has a fixed layout: a living room (default home page), a kitchen (document library), a dining room (list), and a few bedrooms (subsites). The walls are load-bearing—you cannot move them without major structural work. Customizing this house means adding wallpaper (custom CSS), installing a new door (custom master page), or even building an extension (custom web part development). But the core structure remains rigid, and every change requires a contractor (developer) and often breaks the original design. Now, a Modern SharePoint site is like a loft apartment with movable walls. The space is open, and you can rearrange furniture (web parts) by dragging and dropping. You can add a kitchen island (Quick Links web part), a media wall (Hero web part), or a whiteboard (Yammer feed) without any structural changes. The building code (SharePoint framework) ensures everything fits together seamlessly. Importantly, the loft is built on a newer foundation (the SharePoint Online service) that automatically updates, whereas the old house requires manual maintenance. In Microsoft 365, Classic sites are being phased out because they are expensive to maintain and customize, while Modern sites offer flexibility, responsiveness, and integration with Microsoft Teams, Power Platform, and other cloud services. The exam tests your understanding of these differences and why organizations should migrate from Classic to Modern.
What Are SharePoint Modern and Classic Sites?
SharePoint has evolved from an on-premises server product (SharePoint 2010, 2013, 2016, 2019) to a cloud-first platform in Microsoft 365. Classic sites are the legacy site templates from on-premises versions, carried forward for backward compatibility. Modern sites are the new generation, designed for mobile, responsive, and integrated experiences. The term 'Modern' refers to the site architecture, UI framework, and underlying APIs.
Why Two Types Exist
Microsoft introduced Modern sites gradually starting in 2016. The goal was to provide a simpler, faster, and more intuitive experience without requiring custom development. Classic sites remain for scenarios requiring deep customization (e.g., custom master pages, custom web parts built with ASP.NET). However, Microsoft has announced that many Classic features are deprecated and will be removed. For example, Classic publishing sites (Publishing Portal) are no longer available for new sites. The exam emphasizes that Modern is the default and recommended choice.
Key Differences at a Glance
UI Framework: Classic uses SharePoint Server-side rendering with .master pages, .aspx pages, and web parts based on SharePoint Server. Modern uses client-side rendering (SharePoint Framework - SPFx) with React, Angular, or plain JavaScript. The UI is built with Fluent UI (formerly Office UI Fabric).
Responsiveness: Modern sites are fully responsive out of the box—they adapt to any screen size. Classic sites require custom CSS or separate mobile views.
Integration: Modern sites natively integrate with Microsoft Teams, Power Automate, Power Apps, and Microsoft 365 Groups. Classic sites require manual configuration.
Subsites vs. Flat Structure: Classic sites encourage deep hierarchy (site > subsite > subsite). Modern sites promote a flat structure—each site is a 'site' and you use hubs to organize. Subsites are not recommended in Modern.
Customization: Classic allows full control via SharePoint Designer, custom master pages, and server-side code. Modern restricts customization to client-side web parts, themes, and extensions—no server-side code.
Version Support: Classic sites in SharePoint Online are still functional but will eventually be phased out. Modern sites are the focus of all new features.
How Modern Sites Work Internally
Modern sites are built on the SharePoint Online service using the following components:
Site Templates: There are three main Modern templates: Team site (connected to a Microsoft 365 Group), Communication site (for broadcasting information), and modern Team site without a Group. The template determines default pages and features.
Pages: Modern pages are stored as .aspx files but are rendered client-side. Each page is composed of client-side web parts (SPFx). The page layout is defined by a JSON-based schema stored in the page library.
Web Parts: Modern web parts are SPFx components that run entirely in the browser. They fetch data via REST APIs. Examples: Hero, Quick Links, Document Library, Events, Yammer, Microsoft365Feed.
Site Pages Library: The Site Pages library holds all modern pages. Pages can be published with a start and end date, and approval workflow.
Navigation: Modern sites use either top navigation (horizontal bar) or hub navigation. Classic sites use left navigation (tree view) or top navigation with flyouts.
Permissions: Modern team sites inherit permissions from the associated Microsoft 365 Group. Communication sites use SharePoint groups. You can break inheritance as needed.
Classic Sites Architecture
Classic sites rely on the SharePoint Server Object Model. They have a site collection with a root site and optionally subsites. Key elements:
Master Pages: The .master file defines the chrome (header, footer, navigation). Custom master pages allow complete UI replacement.
Page Layouts: Classic publishing pages use page layouts that define content placeholders.
Web Parts: Classic web parts are compiled .NET assemblies deployed as .webpart files. They run server-side and postback to the server.
SharePoint Designer: A desktop tool that allows editing workflows, master pages, and site structure. It is deprecated for Modern sites.
Content Types and Site Columns: Both Classic and Modern use content types, but Classic heavily relies on them for structure.
Migration Path from Classic to Modern
Microsoft provides tools to migrate Classic sites to Modern:
SharePoint Modernization Scanner: Analyzes classic sites and reports on compatibility issues (e.g., custom master pages, custom web parts).
Site Transformation Tool: Converts classic wiki pages to modern pages, converts classic web parts to modern equivalents.
Manual Migration: For heavily customized sites, you may need to rebuild the site using modern templates and reimplement customizations using SPFx.
Exam-Relevant Defaults and Values
Default site template for new sites: Modern Team site (Group-connected) for most users.
Maximum number of sites: 500,000 per tenant (soft limit, can be increased).
Hub sites: Up to 2,000 sites per hub, up to 100 hubs per tenant.
Classic features deprecated: Publishing portal, custom master pages, SharePoint Designer workflows (replaced by Power Automate).
Modern pages support: Up to 300 web parts per page (practical limit lower).
Configuration and Verification
To check if a site is Modern or Classic:
Look at the URL: Modern sites often have /SitePages/Home.aspx while Classic might have /Pages/default.aspx.
In the browser, open the site. Modern sites have a left navigation that collapses, and a top bar with 'New' button. Classic sites have a ribbon at the top.
Using PowerShell:
Connect-PnPOnline -Url https://tenant.sharepoint.com/sites/yoursite
Get-PnPWeb | Select-Object Title, WebTemplate, ConfigurationThe WebTemplate property shows values like GROUP#0 (Modern team site), SITEPAGEPUBLISHING#0 (Modern communication site), or STS#0 (Classic team site).
How Modern Sites Interact with Other Technologies
Microsoft 365 Groups: Modern team sites are backed by a Group. The Group provides a shared mailbox, calendar, and Planner plan.
Microsoft Teams: When you create a Team, a modern site is automatically provisioned as the 'Files' tab.
Power Platform: You can add Power Apps and Power Automate flows directly to modern pages.
Yammer: The Yammer web part allows embedding conversations.
Viva Connections: Modern sites serve as the landing experience for Viva Connections.
Performance Considerations
Modern sites generally perform better because they use client-side rendering and caching. Classic sites with many customizations can be slow due to server postbacks. Modern pages load asynchronously, and web parts are lazy-loaded. The Page Diagnostics for SharePoint tool can analyze performance.
Security and Compliance
Both site types support the same security features: permissions, sharing, and sensitivity labels. However, Modern sites integrate with Microsoft 365 compliance features like retention labels and DLP more seamlessly because they are tied to Microsoft 365 Groups.
Identify Site Type
First, determine whether an existing SharePoint site is Modern or Classic. Open the site in a browser. Look for the left navigation—in Modern sites, it collapses to icons; in Classic, it is a full text tree. Check the URL: Modern team sites have 'SitePages' in the URL; Classic often has 'Pages'. Also, check the site template using PowerShell: `Get-PnPWeb | Select-Object WebTemplate`. 'GROUP#0' or 'SITEPAGEPUBLISHING#0' indicates Modern; 'STS#0' indicates Classic team site. This step is crucial for migration planning.
Assess Customizations
Use the SharePoint Modernization Scanner to identify Classic customizations that block modernization. The scanner checks for custom master pages, alternate CSS, custom web parts, and SharePoint Designer workflows. It outputs a compatibility report. For each issue, decide whether to remove the customization or reimplement it using SPFx. Custom master pages must be removed—Modern sites use a fixed chrome. Custom web parts need to be rebuilt as SPFx client-side web parts. This step determines migration effort.
Plan Site Architecture
Decide on the target Modern site architecture. Classic sites often have deep subsite hierarchies. Modern sites should use a flat structure: each subsite becomes a separate site collection, and you use hub sites to organize them. Determine if the site should be a Team site (with Group) or Communication site. Team sites are for collaboration; Communication sites for publishing. Consider whether to connect to a Microsoft 365 Group, which brings a mailbox and calendar. Hub site association provides shared navigation and search.
Execute Migration
Use the SharePoint Site Transformation Tool (SIT) to automate migration. SIT converts classic wiki pages to modern pages, maps classic web parts to modern equivalents (e.g., Content Editor Web Part to Content Embed web part), and restructures navigation. For pages that cannot be converted, you may need to manually create new modern pages. Migrate document libraries and lists as-is—they are compatible. After migration, test the site thoroughly. Verify that permissions, workflows, and customizations work as expected.
Post-Migration Validation
After migration, validate the site's functionality. Check all pages load correctly in modern view. Test navigation—hub navigation should be set up if needed. Ensure that any custom SPFx web parts are deployed and working. Verify that the site appears in search results. Use the Page Diagnostics tool to check performance. Confirm that integration with Teams (if applicable) is functional. Finally, communicate changes to users and provide training on the new interface.
Enterprise Scenario 1: Migrating a Classic Intranet to Modern
A large enterprise with 10,000 employees has a Classic SharePoint intranet built on SharePoint 2013, now migrated to SharePoint Online but still using Classic templates. The intranet has hundreds of subsites, custom master pages, and numerous custom web parts. The problem: the Classic site is slow, not mobile-friendly, and users struggle with the outdated UI. The IT team decides to migrate to Modern Communication sites. They use the Modernization Scanner to identify customizations: 50 custom web parts, 10 custom master pages, and 30 SharePoint Designer workflows. They rebuild the web parts as SPFx solutions, remove master pages (accepting the default Modern chrome), and replace workflows with Power Automate flows. They flatten the hierarchy: each department gets its own Communication site, and they create a hub site for the corporate intranet. The migration takes 6 months. Post-migration, page load time drops from 8 seconds to 2 seconds, mobile usage increases by 40%, and user satisfaction improves.
Enterprise Scenario 2: Team Collaboration with Modern Team Sites
A mid-size company (500 users) uses Classic team sites for project collaboration. Each project has a site with subsites for phases. Users complain about navigation and difficulty finding documents. The IT admin creates a new Modern team site for each project, connected to a Microsoft 365 Group. They use the hub site feature to link related projects. The flat structure simplifies navigation, and the Group integration provides a shared calendar and Planner for task management. The admin adds Power Automate flows to notify the team when documents are updated. The migration is straightforward because the Classic sites had minimal customizations. The main challenge is user adoption—training users on the new interface. The admin creates a quick-start guide and holds lunch-and-learn sessions.
Common Pitfalls
Ignoring customizations: Trying to migrate a heavily customized Classic site without rebuilding custom web parts leads to broken functionality.
Deep hierarchy: Keeping subsite structure in Modern sites defeats the purpose. Always flatten.
Not testing: Post-migration, some web parts may not render correctly. Always test on a pilot group.
Performance: Too many web parts on a modern page can slow it down. Keep web parts under 20 per page.
What MS-900 Tests on This Topic
The MS-900 exam objective 2.3 'Describe the capabilities of Microsoft 365 productivity solutions' includes SharePoint Modern vs Classic. Specifically, you should know:
The differences between Modern and Classic sites (UI, customization, integration)
Which site type is recommended for new sites (Modern)
The benefits of Modern sites (mobile, integration, simplicity)
The migration tools available (Modernization Scanner, Site Transformation Tool)
That Classic features are being deprecated (e.g., custom master pages, SharePoint Designer workflows)
Common Wrong Answers and Why Candidates Choose Them
'Classic sites offer better performance' – Candidates confuse server-side rendering with faster load times. In reality, Classic sites with customizations are slower due to postbacks. Modern sites use client-side rendering and caching, making them faster.
'Modern sites require custom development' – This is false. Modern sites are designed to be customized without code using web parts. Classic sites often require custom development for advanced customizations.
'Subsites are recommended in Modern sites' – The opposite is true. Modern sites promote a flat structure; subsites are legacy. Candidates who remember on-premises hierarchies choose this wrong answer.
'Classic sites are fully responsive' – Classic sites are not responsive out of the box. Modern sites are fully responsive.
Specific Numbers and Terms That Appear on the Exam
Site templates: 'Team site' and 'Communication site' are the two modern templates.
Hub sites: Up to 2,000 sites per hub, up to 100 hubs per tenant.
Maximum sites: 500,000 per tenant (soft limit).
Deprecated features: Publishing portal, custom master pages, SharePoint Designer workflows.
Migration tools: 'SharePoint Modernization Scanner' and 'Site Transformation Tool'.
Group-connected site: Modern team site that is connected to a Microsoft 365 Group.
Edge Cases and Exceptions
Classic publishing sites: Still exist but cannot be created new. Exam may ask if you can create a new publishing site—answer is no.
Hybrid scenarios: If a tenant has on-premises SharePoint, Classic sites may be needed for hybrid features. But MS-900 focuses on cloud.
Customizations: Some classic customizations (like custom web parts) can be migrated to SPFx, but others (like custom master pages) cannot. The exam tests that custom master pages are not supported in Modern.
How to Eliminate Wrong Answers
Use the underlying mechanism: Modern sites are built on client-side technology, integrated with Microsoft 365 services, and designed for mobile. If an answer suggests Classic is better for mobile or integration, eliminate it. If an answer says Classic is the default for new sites, eliminate it. Remember that Microsoft is deprecating Classic features, so any answer promoting Classic as the future is wrong.
Modern sites are the default and recommended site type for new SharePoint sites in Microsoft 365.
Classic sites are legacy and many features are deprecated; they are only retained for backward compatibility.
Modern sites are fully responsive and mobile-friendly; Classic sites are not.
Modern sites integrate natively with Microsoft Teams, Power Automate, Power Apps, and Microsoft 365 Groups.
Custom master pages and server-side code are not supported in Modern sites; use SPFx for customizations.
Migration from Classic to Modern can be automated using the SharePoint Modernization Scanner and Site Transformation Tool.
Hub sites allow organizing up to 2,000 sites per hub with shared navigation and search.
The two main Modern site templates are Team site (with or without Group) and Communication site.
These come up on the exam all the time. Here's how to tell them apart.
Modern Site
Client-side rendering using SPFx
Fully responsive out of the box
Flat site structure; no subsites recommended
Integrated with Microsoft 365 Groups, Teams, Power Platform
Customization via client-side web parts and themes
Classic Site
Server-side rendering with .master pages
Not responsive; requires custom CSS
Hierarchical structure with subsites
Limited integration; manual setup required
Customization via SharePoint Designer, custom master pages, server-side code
Mistake
Classic sites are faster than Modern sites because they use server-side rendering.
Correct
Modern sites are generally faster because they use client-side rendering, caching, and asynchronous loading. Classic sites with customizations often have slow postbacks and full page reloads.
Mistake
Modern sites cannot be customized at all.
Correct
Modern sites can be customized using SPFx web parts, themes, and extensions. They do not allow server-side code, but client-side customization is powerful and supported.
Mistake
Subsites are recommended for organizing content in Modern sites.
Correct
Modern sites promote a flat structure. Subsites are legacy and not recommended. Use hub sites to organize multiple site collections.
Mistake
You can still create new Classic publishing sites in SharePoint Online.
Correct
Microsoft has disabled creation of new Classic publishing sites. Existing ones remain, but you cannot create new ones.
Mistake
Classic sites are fully responsive on mobile devices.
Correct
Classic sites are not responsive out of the box. They require custom CSS or separate mobile views. Modern sites are fully responsive by default.
Reveal each answer, then mark whether you got it right. Score 60%+ to unlock the next chapter.
Yes, you can migrate content from Classic to Modern sites. Use the SharePoint Site Transformation Tool to convert pages and web parts. Document libraries and lists are compatible and can be moved using built-in migration tools. However, custom master pages and server-side customizations must be replaced. The tool automates most of the process, but some manual work may be required for heavily customized sites.
Classic sites will continue to function for now, but Microsoft is gradually deprecating Classic features. For example, you cannot create new Classic publishing sites. Microsoft recommends migrating to Modern sites to avoid future disruption. Eventually, Classic sites may be fully retired, but no date has been announced. The exam emphasizes that Modern is the future.
A Team site is designed for collaboration among a group of users. It can be connected to a Microsoft 365 Group, providing a shared mailbox, calendar, and Planner. A Communication site is for broadcasting information to a wider audience, like an intranet homepage. Communication sites do not have a Group and are typically used for one-way communication.
Technically, you can create subsites in Modern sites, but it is not recommended. Microsoft advises a flat architecture where each subsite becomes a separate site collection. Use hub sites to organize them. Subsites in Modern sites are considered a legacy behavior and may not be fully supported in the future.
A hub site is a central site that connects related sites. It provides shared navigation, branding, and search across all associated sites. Up to 2,000 sites can be associated with a hub. Hub sites help organize content without using subsites. They are a key feature of Modern site architecture.
You can check the site template using PowerShell: `Get-PnPWeb | Select-Object WebTemplate`. Values like 'GROUP#0' or 'SITEPAGEPUBLISHING#0' indicate Modern. 'STS#0' indicates Classic team site. Also, in the browser, Modern sites have a left navigation that collapses to icons, while Classic has a full text tree.
No. SharePoint Designer workflows are deprecated and not supported in Modern sites. They should be replaced with Power Automate flows. The exam tests that Power Automate is the recommended solution for automation in Modern sites.
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