SharePoint Online shows "Tenant sites are in read-only right now" and "Storage quota exceeded" although tenant storage is available

Run Microsoft 365’s SharePoint Tenant Storage diagnostic first, because it specifically checks discrepancies between the tenant quota displayed in the SharePoint admin center and the quota actually allocated and enforced by the service.

1. Validate the effective tenant quota

1. Sign in to the Microsoft 365 admin center with a Microsoft 365 administrator account.
2. Open Help & support, search for SharePoint Tenant Storage, and run the diagnostic.
3. Review:
   • Allocated tenant storage
   • Current usage
   • How the quota is allocated
   • Any detected quota-calculation or provisioning issue
4. Apply any recommended correction, then rerun the diagnostic.

The diagnostic requires an administrator account and is unavailable in GCC High, DoD, and Microsoft 365 operated by 21Vianet environments.^1^

Also compare its result with SharePoint admin center → Sites → Active sites. The storage bar in the upper-right shows total and available organizational storage. Be aware that recent storage changes can take 24–48 hours to appear there.^2^

If the diagnostic reports the tenant is genuinely over quota, restore capacity by purchasing eligible additional storage or licenses, archiving inactive content, or deleting content that is no longer required. A non-EDU tenant’s allocation is generally 1 TB plus 10 GB for each eligible purchased license, plus Extra File Storage add-ons.^3^

2. If tenant capacity is available, check effective site limits

Available pooled capacity does not prevent a site from reaching its own quota when storage management is configured as Manual.

1. Go to SharePoint admin center → Settings → Site storage limits.
2. Check whether storage management is:
   • Automatic: sites draw from the central tenant pool as needed.
   • Manual: each site has an independently configured limit.
3. If it is Manual, go to Sites → Active sites.
4. Select an affected site, including affected Teams-connected sites.
5. On General → Storage limit, select Edit and compare its configured limit with its usage.
6. Increase the limit where appropriate, or switch the tenant to Automatic and save.

Switching from manual to pooled automatic storage resets individual limits to 25 TB, although that does not increase the organization’s actual total storage entitlement.^2^

For an affected user’s OneDrive, separately inspect Microsoft 365 admin center → Users → Active users → select the user → OneDrive. Individual OneDrive quota exhaustion is distinct from tenant pooled-storage exhaustion and must be corrected by increasing that user’s supported quota or reducing usage.^4^

3. If quotas are correct, test for site locks

The read-only message can also indicate that sites have an explicit lock state.

1. In Microsoft 365 admin center → Help & support, run the Locked Site diagnostic against an affected URL.
2. If a site is explicitly locked and no closure policy applies, a SharePoint administrator can unlock it with SharePoint Online Management Shell:

Connect-SPOService -Url "https://contoso-admin.sharepoint.com"

Set-SPOSite `
  -Identity "https://contoso.sharepoint.com/sites/Example" `
  -LockState Unlock

Do not mass-unlock sites merely because they are read-only; first confirm that LockState is the condition reported. An unlock command does not work when a site was made read-only through a site-closure policy.^5^

4. Check service health if no quota or lock issue is found

When affected sites are not locked and the tenant diagnostic finds no storage problem, check:

• Microsoft 365 admin center → Health → Service health
• Microsoft 365 admin center → Health → Message center

The maintenance-style read-only message can represent tenant maintenance when no lock state exists.^6^

If no advisory appears and the problem remains tenant-wide, open a Microsoft 365 support request and attach:

• Tenant Storage diagnostic result
• Storage bar showing total, used, and available capacity
• Storage-management mode: Automatic or Manual
• Results for several affected SharePoint and OneDrive URLs
• Exact timestamps and correlation/request IDs
• Screenshots with tenant and user identifiers removed

References

1. Self-help diagnostics for SharePoint Online and OneDrive administrators
2. Manage site storage limits in SharePoint in Microsoft 365
3. SharePoint in Microsoft 365 Out of Storage Space - SharePoint
4. OneDrive site is read-only because storage quota was exceeded
5. Lock and unlock sites
6. SharePoint or OneDrive read-only error messages - SharePoint