Modern SharePoint Hub Sites: Why They Replaced Subsites and How They Fix Classic URL Hierarchies

Hub sites in modern SharePoint Online solve a problem that classic SharePoint created: rigid, deep site hierarchies that were hard to change.

If your organization started with classic SharePoint, you may still see those old structures around. Understanding what hubs replace will help you design better site architecture going forward.

This post explains:

• How classic SharePoint used subsites
• Why deep hierarchies became a problem
• How modern SharePoint changes the model
• Where hub sites fit in

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Classic SharePoint: subsites as the only way to organize

In classic SharePoint, you didn’t have much choice. All team sites lived under a single site collection, arranged in a hierarchy.

A common pattern looked like this:

• One top‑level site collection for team sites
• Under it, department sites as subsites:
  • /sites/finance
  • /sites/manufacturing
  • /sites/hr
  • /sites/it
• Under each department, child sites for teams or functions:
  • /sites/it/helpdesk
  • /sites/it/projects
  • /sites/it/security
• Under those, more subsites for specific projects, products, or work areas.

This is how organizations created structure: by nesting sites under sites.

Why this became a problem

The subsite model caused two major issues:

1. URL-based hierarchy
2. Inflexible structure when the organization changed

Let’s look at both.

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The URL problem: long, fragile addresses

In classic SharePoint, structure was tightly tied to URLs. Each level added more to the address.

For example:

• Top-level site:
  • orgname.sharepoint.com/sites/finance
• Child site (payables):
  • orgname.sharepoint.com/sites/finance/payables
• Team site under that (vendors team):
  • orgname.sharepoint.com/sites/finance/payables/vendors
• Default document library:
  • orgname.sharepoint.com/sites/finance/payables/vendors/Documents

This grows quickly. There is a limit to how long URLs can be, so admins had to compress names:

• finance → fin
• payables → pay
• documents → docs

There were even sessions and guidance focused on naming conventions just to keep URLs under the limit. The trade‑off was:

• Short URLs that no one understands, or
• Descriptive URLs that risk hitting length limits and breaking.

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The structure problem: hard to move or reorganize

The second issue was inflexibility.

Because sites were nested under other sites:

• To create a new IT project site, you had to go to the IT site and intentionally create a subsite.
• That subsite’s URL permanently reflected its position in the tree.

When the business changed, the structure did not adapt easily. For example:

• You create a Vendors site directly under Finance.
• Later, Finance splits into Payables and Receivables.
• You want Vendors to sit under Payables.

Originally, moving a subsite like that was either:

• Not supported at all, or
• Only possible with third‑party tools.

Support for moving sites improved over time, but it remained complex and risky. Reorganizing a live SharePoint hierarchy to reflect real organizational changes could be:

• Time‑consuming
• Error‑prone
• Expensive

It became clear that relying on nested subsites and URL structure was not sustainable.

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Modern SharePoint: flat sites with short URLs

Modern SharePoint changes the model:

• Each site is its own site collection.
• Site URLs are short and flat:
  • orgname.sharepoint.com/sites/sitename

You no longer create layers of subsites to show relationships. Instead, you:

• Create independent sites for departments, projects, and teams.
• Use navigation, shared branding, and hub sites to connect them.

Benefits of this approach:

• You avoid deep, fragile URL paths.
• Site names can be clear and readable.
• You can change how sites relate to each other without renaming or moving subsites in a hard hierarchy.

This is where hub sites come in: they provide a way to group related sites logically without nesting them under each other in the URL.

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What hub sites give you (high level)

You’ll see more detail in the next parts of your training, but at a high level hub sites:

• Group related sites (for example, all HR‑related sites)
• Provide shared navigation across those sites
• Support consistent branding and theme
• Roll up content (news, events, etc.) from associated sites into one place

Instead of using subsites under /sites/hr, you:

• Create separate sites like:
  • orgname.sharepoint.com/sites/HR
  • orgname.sharepoint.com/sites/Benefits
  • orgname.sharepoint.com/sites/Recruiting
• Associate them to a HR hub.

Users get a unified experience without forcing everything into a single subsite tree.

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Summary

Classic SharePoint used subsites and URL paths to organize content. This led to:

• Deep, hard‑to‑manage hierarchies
• Long, fragile URLs
• Difficulty reorganizing when the business changed

Modern SharePoint solves this by:

• Making each site its own site collection with a short URL
• Using hub sites to connect related sites for navigation, branding, and content rollup

If you still have classic structures in your tenant, hub sites are your path forward to a more flexible, maintainable information architecture.