Word and PowerPoint files in SharePoint Online allow up to 99 simultaneous editors. That ceiling is rarely the limiting factor. More often, admins encounter co-authoring failures caused by file type restrictions, checkout settings, or workbook features that silently revert a document to single-editor mode. The tables below cover each scenario.
Co-authoring support by file type
| File type | Co-authoring supported | Max simultaneous editors | Notes |
|---|---|---|---|
| Word (.docx, .docm) | Yes | 99 | Full real-time co-authoring in Word for the Web and Word desktop with AutoSave enabled. |
| PowerPoint (.pptx, .pptm) | Yes | 99 | Real-time co-authoring in PowerPoint for the Web and PowerPoint desktop. |
| Excel (.xlsx) | Yes | Not fixed; depends on workbook features | Co-authoring is available but is disabled by specific Excel features. See the table below for disqualifying features. |
| OneNote (.one) | Yes | No limit stated | OneNote uses section-level sync rather than true co-authoring. Multiple users can add and edit content simultaneously; merges are handled per section. |
| Visio (.vsdx) | Limited | Varies | Co-authoring is available in Visio for the Web. Desktop Visio client support depends on the subscription plan and file complexity. |
| Word legacy (.doc) | No | 1 (exclusive checkout) | Legacy format. Opening a .doc file in Word desktop triggers a checkout, blocking other editors. Convert to .docx to enable co-authoring. |
| Excel legacy (.xls) | No | 1 (exclusive checkout) | Legacy format. Same checkout behaviour as .doc files. Convert to .xlsx to enable co-authoring. |
| PowerPoint legacy (.ppt) | No | 1 (exclusive checkout) | Legacy format with the same checkout restriction as other legacy Office formats. |
| Macro-enabled workbook (.xlsm) | Limited | Depends on macro content | Workbooks with VBA macros may support co-authoring if no macro actively locks the file. Many common macro patterns disable co-authoring silently. |
| PDF, ZIP, images, video | No | 1 (exclusive checkout) | Non-Office files do not support co-authoring in SharePoint. They are opened exclusively; a second user opening the file while it is in use receives a read-only copy. |
What disables SharePoint co-authoring?
Several conditions cause SharePoint or Office to fall back to exclusive checkout mode even on a supported file type. When co-authoring falls back, the first editor retains write access and all subsequent openers receive a read-only copy.
| Condition | Affected file types | Result |
|---|---|---|
| File is checked out by a user | All types | Co-authoring unavailable for the duration of the checkout. Only the person who checked out the file can edit it. |
| Library has "Require Check Out" enabled | All types | Every file in the library must be checked out before editing, which blocks co-authoring across the entire library. |
| Information Rights Management (IRM) applied to the library | Word, Excel, PowerPoint | IRM enforces checkout and disables AutoSave, blocking co-authoring. Files open in read-only until checked out. |
| Legacy Excel Shared Workbook feature enabled | Excel (.xlsx) | The legacy Share Workbook feature (pre-2016) is incompatible with modern co-authoring. Removing it restores co-authoring. |
| File opened in older desktop application | Word, Excel, PowerPoint | Office 2010 and earlier do not support co-authoring. A user on an older client triggers an exclusive lock visible to other editors as a checkout notification. |
| AutoSave disabled in the desktop client | Word, Excel, PowerPoint | Without AutoSave enabled, the desktop client does not participate in real-time co-authoring even if the file type supports it. The file is effectively in exclusive edit mode from the server's perspective. |
| Password protection on the document | Word, Excel, PowerPoint | Password-protected files cannot be co-authored. The file must be opened with the password and is then treated as a single-user edit session. |
Co-authoring and version history: the storage impact
Active co-authoring sessions generate version history at a much higher rate than single-author editing. AutoSave commits changes to SharePoint roughly every 30 seconds per active editor. A document being edited simultaneously by four users for two hours can accumulate several hundred version entries in that session alone.
Those auto-saved versions are stored identically to manually saved versions and count against the site's storage quota. Review version limits for any library with active co-authoring. The default SharePoint Online limit of 500 major versions per file fills significantly faster in co-authoring libraries than in those used by single authors - AutoSave sessions from multiple editors can exhaust the cap within a single working day on large documents.
| Scenario | Approximate versions generated | Storage impact |
|---|---|---|
| Single user, 1-hour editing session | 40 - 80 versions | Low; each version is a delta from the previous |
| 4 co-authors, 2-hour session | 200 - 400 versions | Moderate; each autosave from each user creates an entry |
| 10 co-authors, full-day working document | 500 - 1,500+ versions | High; version history hits the default 500-version cap within the session for large documents |
When version history from co-authoring sessions is accumulating faster than it can be managed manually, a bulk trim across all affected libraries is the practical fix. See the SharePoint versioning defaults reference for per-library version settings and the guide on trimming SharePoint version history in bulk for the step-by-step process.
Frequently Asked Questions
How many people can edit a SharePoint document at the same time?
Word and PowerPoint documents stored in SharePoint Online support up to 99 simultaneous co-authors. Excel workbooks support co-authoring for multiple concurrent users, but certain features such as legacy shared workbooks or Information Rights Management will disable co-authoring and revert the file to exclusive checkout mode.
Why does SharePoint co-authoring fill up version history so quickly?
During a co-authoring session, AutoSave commits changes to SharePoint every few seconds and each commit creates a version entry. A document edited by four users over two hours can accumulate several hundred version entries. Those versions count against site storage quota identically to manually saved versions. Libraries with active co-authoring should have version limits reviewed regularly to prevent runaway storage growth.
Does requiring check-out on a SharePoint library disable co-authoring?
Yes. When a document library has Require Check Out enabled, users must check out a file before editing. A checked-out file is locked to a single editor and cannot be co-authored. Admins who need version control alongside collaborative editing should use a version limit policy with AutoSave rather than mandatory checkout.
Learn more about Space Master version and storage management