How SharePoint storage works
SharePoint and Teams files draw from a pool of storage shared by the whole tenant. The pool has a base allowance plus extra for each licensed user, so a business that has grown its licences has grown its storage too. OneDrive storage is separate and allocated per user. Check current figures in Microsoft's documentation, as allowances have changed over time.
When the tenant pool runs low, admins get warnings, and if it runs out, sites can become read-only, which stops people saving files. That usually happens without much notice in small businesses, because nobody watches the storage figure until uploads start failing on a Monday morning before a deadline. A storage alert set well below the limit turns that crisis into a routine task scheduled for a quiet week.
Find out what is using the space
Open the SharePoint admin centre and sort active sites by storage used. In most tenants a small number of sites account for most of the space. Then look inside those sites using the storage metrics page in site settings, which shows the size of each library and folder, including version history and the recycle bin.
Typical culprits are a migrated shared drive full of old projects, design or video files saved repeatedly with many versions, photo collections, large database files that change often, and a recycle bin full of recently deleted material. Teams meeting recordings saved to OneDrive or SharePoint can also add up quickly in businesses that record regularly.
Version history is often the hidden cost
Every saved version of a file counts against storage. A 50 MB spreadsheet saved a few hundred times, with AutoSave creating versions as people work, can quietly take several gigabytes. Design files, presentations with embedded video and large Excel models are the usual offenders. The storage metrics page shows version size separately so you can see how much is old versions.
Admins can set version limits per library or across the tenant, including newer options that automatically trim older versions by age and count. Lowering limits on the few libraries holding large, frequently edited files often frees a large amount of space without affecting ordinary documents. Check that your backup covers what you need before trimming, because trimmed versions are gone.
Archive and clean up
Old project folders and finished client work rarely need to live in the active working area. Agree a retention rule with management, such as keeping completed projects for seven years, then move older material into an archive. That might be a separate site with read-only access, Microsoft's archiving feature for inactive sites where available, or a cheaper storage option outside SharePoint.
Look for duplicates, especially after a migration where the same folder was copied twice or both a zip file and its extracted contents were uploaded. Empty recycle bins only once you are sure nothing in them is needed. Delete personal media collections that were never meant to be on the business system, after giving their owners notice.
Buying more storage
Microsoft sells extra SharePoint storage per gigabyte per month as an add-on. It is a reasonable option when a business genuinely needs to keep large volumes of active files online. Check current pricing, because costs add up over years for data that may be rarely touched. Work out the yearly cost of the add-on at your current growth rate before treating it as the easy answer.
For large archives that nobody opens often, cheaper options such as Microsoft's archiving features, Azure storage or a NAS with an offsite backup may make more sense. The right choice depends on how often the data is accessed and who needs it. A mix is common: active work in SharePoint, closed projects in an archive.
Stop it filling up again
Set up storage alerts so admins are warned well before limits are reached, and look at the storage report each quarter. Agree where large media files belong before people start saving them. For video-heavy teams, consider whether a dedicated platform suits better than SharePoint for raw footage, with only the finished versions saved back to the team library where everyone can find them.
Give site owners responsibility for their own site's size and an annual tidy-up. Small businesses that do this rarely run out of storage, and when they do grow, the decision to buy more is deliberate rather than an emergency. If you would like a second set of eyes on where your storage is going, the Office IT health check includes a storage review.
In short
- SharePoint storage is a shared tenant pool that grows with licences.
- A few sites usually use most of the space; check storage reports.
- Version history on large files is a common hidden cost.
- Archive finished work and clear duplicates before buying more.
- Set storage alerts and review usage each quarter.