Because Word and Excel are running in a browser, do not repair or reinstall desktop Office; first determine whether the failure follows the document or the browser session.
1. Separate a file problem from a browser problem
- From the Microsoft 365 home page, create a new blank Word document and a new blank Excel workbook.
- Open a different existing Word or Excel file.
- Interpret the result:
- Only one document fails: continue with File-specific checks below.
- All existing documents fail, but new files work: the existing files may use an unsupported format or feature.
- New and existing files all fail: skip to Reset the browser session.
2. File-specific checks
Check the filename extension:
- Word for the web supports
.docx; it can also open and convert .doc. Templates such as .dotx and .dotm cannot be edited in the browser.
- Excel for the web supports
.xlsx and .xlsb. Support for older or specialized formats is limited. ^1^
For an affected Excel workbook containing macros, XML maps, or other unsupported features:
- Select Open in Excel if the error offers that option.
- If the file opens but cannot be edited online, select Edit a Copy to create a browser-compatible copy.
- Give the copy a different filename. Do not replace the original, because unsupported features are removed from the copy. ^2^
If no desktop Office application is installed, ask the file owner to save and resend it as:
- Word:
.docx
- Excel:
.xlsx or .xlsb
Converting a macro-enabled Excel file to .xlsx removes its macros, and macros do not run in Excel for the web. ^1^
If the same file also fails for another user or in another browser, the file may be damaged. Open and Repair is available only in a desktop Office application under File > Open > Browse > select the file > arrow beside Open > Open and Repair. ^3^
3. Reset the browser session
If every Word and Excel file fails, clear Microsoft 365 site data rather than repairing Office.
In Microsoft Edge:
- Select Settings and more (…) > Settings > Privacy, search, and services.
- Select Cookies > See all cookies and site data.
- Search for the Microsoft 365/Office, OneDrive, and SharePoint sites you use.
- Delete their stored cookies and site data.
- Close all Edge windows, reopen Edge, sign in again, and test a newly created document.
Deleting cookies signs you out, but deleting only the affected sites avoids clearing unrelated browser data. ^4^
Also test once in an InPrivate window. If documents work there, the normal browser profile’s stored site data or an extension is implicated; disable extensions individually or reset that profile’s Microsoft site data.
4. If the problem remains
- Work or school account: ask the Microsoft 365 administrator to check the Service health dashboard for Word, Excel, OneDrive, or SharePoint incidents.
- Personal account: contact Microsoft Support and provide:
- the complete error text;
- browser name and version;
- whether blank files work;
- whether the same document fails in another browser;
- the affected file extensions.
Do not include the documents themselves unless requested through an authorized support channel.
References
- Unable to View or Edit Office files by using Office Online or Office Web Apps | Microsoft Support
- Edit a workbook that contains features unsupported by Excel for the web | Microsoft Support
- Open a document after a file corruption error | Microsoft Support
- Manage cookies in Microsoft Edge: View, allow, block, delete and use | Microsoft Support