Excel cant open file because the file extension is invalid

Occasional Contributor

My PC crashed and auto rebooted while i jut saved my file in microsoft one drive and i cant seem to reopen it again. I guess the data must be corrupted. How can i recover it?

12 Replies
Is there no way for me to upload the excel file here?



You wrote: 

My PC crashed and auto rebooted while i jut saved my file in microsoft one drive and i cant seem to reopen it again.


Hard to diagnose without a bit more data (and even with more data, the cause may be elusive). But let me ask a few diagnostic questions:

  1. Has this happened before?
  2. Have you done a cold re-boot (not just the auto-reboot you mention)?
  3. Can you open other Excel files currently? (i.e., is it just this one file?)
  4. What (generally) is different or distinctive about this file compared with others that you typically work with? (size, nature of data, presence of absence of VBA, macros, etc.)
  5. What about other MS Office applications and files? Are they all working normally, files can be saved, re-opened.
  6. How about non-Office files.
  7. What edition of Excel are you using?
  8. What PC and windows OS?

To your subsequent question about posting files, it can be difficult at times. If it becomes necessary, you would be able to grant access to folks to your file on OneDrive (if you use it) or DropBox, or other such file sharing systems. But let's start with answers to those questions. (And if there's other information you can provide, please do)

1. Never happened before
2. Yes, i did
3. Yes, the other files can be opened normally
4. No difference from the other files in the same folder. It only uses simple formulas.
5. Yes, everything else is working normally
6. It's just this one file that is not opening
7. Excel 365
8. HP Pavilion & Windows 11

In the header to this all, you do mention the words "because the file extension is invalid"


I should have asked, (or you could have provided as well) --

  1. what is that invalid file extension? Is Excel giving that as a reason for not opening?
  2. Could you make a copy of the file and then change the extension to a valid extension (.xlsx)
  3. and see if that opens
The extension is xlsx. I tried to change it to xls as per an online recommendation but it doesn’t work.

@KPD22   If the extension IS xlsx it's not clear how/why/when you're getting the message that it's invalid.


I encounter regularly this "Alert" when trying to open a file that I get from a financial institution.


Are you getting a message like that? Not identical maybe, but similar?

In my case, I DO trust the data and its source, so open it without trouble.


So I'm reaching the end of my ability to offer suggestions, but there may be others here with ideas. You could help by giving a more complete description of the scenario--timing of crash, what kind of error message or alert you're getting when you try to open. Attach images if a file can't be attached.




Attached is the screenshot of the error.excel_error.png

I'm afraid I have no idea what you'd need to do next. Let's hope somebody else can chime in.

@mathetes showing this alert while opening microsoft excel. Pls suggest to restore the settings 

"this alert"

Not terribly specific.
i have same problem w/ this ones



i have same problem w/ this ones


There were several different descriptions given earlier in this thread. So you'll need to be a bit more specific/descriptive, maybe include a screen image...  Maybe add a description of the file you're trying to open, what you believe or know it to be, what its source is...