Site owners in SharePoint sometimes see a storage quota warning on a site that does not appear to be running out of space. The warning may say the site is near its storage limit or has exceeded its quota even when the site has plenty of room. This mismatch happens because SharePoint calculates storage at the tenant level and then distributes the quota across all sites. This article explains how tenant-level storage pooling works, why the warning can appear on the wrong site, and what steps site owners should take to verify and resolve the issue.
Key Takeaways: Storage Quota Warnings in SharePoint
- SharePoint admin center > Active sites > Storage limit: Shows the per-site storage quota set by the tenant admin.
- SharePoint admin center > Settings > Storage management: Displays the total tenant storage pool and how much is used.
- Site collection usage report in SharePoint admin center: Lists storage usage per site and helps identify which site triggered the warning.
Why the Storage Quota Warning Appears on the Wrong Site
SharePoint Online uses a shared storage pool model. The tenant admin buys a fixed amount of storage for the entire organization. This total includes base storage plus any additional purchased storage. The admin can then set individual storage limits on each site collection. These limits do not reserve space. They act as a cap that triggers a warning when a site reaches the limit. But the warning is tied to the tenant pool, not the individual site limit.
When the total used storage across all sites approaches or exceeds the tenant pool, SharePoint sends a quota warning to the site owners of the site that most recently increased in size. That site may not be the one using the most storage. It is simply the site whose last growth pushed the tenant pool over the threshold. This behavior confuses site owners who check their own site usage and see plenty of free space.
The Tenant Storage Pool Mechanism
SharePoint Online aggregates storage from all sites, including team sites, communication sites, and OneDrive accounts. The tenant admin sees a single number in the SharePoint admin center under Settings > Storage management. The warning email or banner that site owners receive references this tenant-level usage. If the tenant pool is at 95 percent or above, the system sends warnings to site owners of sites that have grown recently. The system does not send warnings to every site owner. It selects the site that caused the latest increase.
Why the Warning Points to the Wrong Site
The site owner checks the site storage quota in Site settings > Storage metrics. The page shows the site has used only 2 GB of a 25 GB limit. Yet the warning says the site is over quota. The discrepancy exists because the warning is based on the tenant pool, not the site limit. The site owner cannot see the tenant pool usage from the site settings page. They need to check the SharePoint admin center or ask the tenant admin.
Steps to Identify the Real Cause of the Storage Warning
- Check the warning message details
Read the full warning email or banner. Look for the phrase “Your site is running out of storage” or “Storage quota exceeded.” Note the date and time the warning was sent. The warning includes a link to the site storage metrics page, but that page shows only the site-level quota. - Open the SharePoint admin center
Go to SharePoint admin center > Active sites. Find the site that received the warning. Look at the Storage limit column. This number is the per-site quota set by the admin. Compare it with the Storage used column. If the used amount is below the limit, the site is not the source of the problem. - View tenant storage usage
In the SharePoint admin center, go to Settings > Storage management. This page shows the total storage available for the tenant and the total used. If the used amount is near or above the total, the tenant pool is full. The warning is a tenant-level alert. - Identify which site triggered the warning
Ask the tenant admin to run the Site collection storage usage report. This report lists every site and its storage usage sorted by size. The site with the largest recent increase is likely the one that pushed the tenant pool over the threshold. The warning was sent to that site’s owner, not to the site that uses the most storage overall. - Request a tenant storage increase if needed
If the tenant pool is full, the tenant admin must purchase additional storage through the Microsoft 365 admin center. Go to Billing > Purchase services and add more SharePoint storage. The admin can also free up space by deleting old site collections or reducing file versions.
If the Storage Warning Persists After Checking the Tenant Pool
Site Owner Sees the Warning but the Tenant Pool Is Not Full
If the tenant pool has plenty of free space but the site still shows a warning, the issue may be a stale cache or a delayed sync. Wait 24 hours. SharePoint recalculates storage usage once per day. If the warning remains after 24 hours, ask the tenant admin to check the site quota in the admin center. The admin can manually set a higher per-site limit on the Settings page of the site in the admin center.
Multiple Sites Receive the Same Warning Simultaneously
When several site owners report the same warning at the same time, the tenant pool is likely full. The system sends warnings to multiple site owners in this case. The tenant admin should follow the steps above to check the storage management page and purchase additional storage or clean up old content.
The Site Storage Metrics Page Shows Incorrect Usage
The storage metrics page under Site settings > Storage metrics may show a value that is lower than what the admin center displays. This happens because the metrics page updates less frequently. Use the admin center numbers as the authoritative source. If the admin center shows the site is under its limit, the site is fine.
Tenant Storage Pool vs Per-Site Quota: Key Differences
| Item | Tenant Storage Pool | Per-Site Quota |
|---|---|---|
| Description | Total storage available for all SharePoint sites and OneDrive in the organization | Storage limit set on an individual site collection |
| Who sets it | Microsoft 365 tenant admin via billing | Tenant admin or site admin in site settings |
| Where to check | SharePoint admin center > Settings > Storage management | Site settings > Storage metrics or admin center > Active sites > Storage limit |
| Triggers quota warning | When total used exceeds 95% of the pool | When site used storage exceeds the per-site limit |
| Warning recipients | Site owners of the site that most recently grew | Site owner of that specific site |
A site owner who sees a warning but has free space on their site should check the tenant pool. The warning is likely a tenant-level alert. The tenant admin must resolve the issue by increasing the pool or freeing up space. Site owners can also request a higher per-site quota if the tenant pool has capacity, but the warning will not disappear until the tenant pool usage drops below 95 percent.