SharePoint Online showing blank page on Firefox 99.0

Occasional Contributor

Hey All,


Is anyone else experiencing dead end page loads for any SharePoint Online destination when using Firefox version 99.0?


If I browse to the standard https://<domain>  page I get nothing but a blank page. There's an initial 200 response but then nothing. It takes almost 5 minutes to tell me it couldn't load the page.


I can get content if I 'force' refresh the page but then if you visit another sharepoint page, the same thing happens until you 'force' refresh the next page?


The most consistent error message I get is this one:

Failed to load ''. A ServiceWorker intercepted the request and encountered an unexpected error.
Any ideas?
6 Replies
I'm guessing someone saw this and correlated this with a bunch of support requests. Here's the latest if anyone is following this:

April 13, 2022 7:33 AM
Title: Users can't load modern SharePoint Online sites when using the Firefox browser

User Impact: Users are unable to load SharePoint Online modern sites when using the Firefox browser.

More info: Users can load modern sites with private browsing in Firefox or use any other web browser.

Current status: We've completed development and validation of the code fix. Additionally, we've started to deploy the fix to the affected environment and we suspect that the fix will complete saturation by our next update.

Scope of impact: This issue may impact any user attempting to load SharePoint Online modern sites when using Firefox browser versions 99.0 and above.

Estimated time to resolve: Based on current deployment progress, we expect this problem to be resolved by Wednesday, April 13, 2022, 1:00 PM (3:00 AM UTC).

Root cause: A navigation preload problem is preventing users from loading SharePoint Online modern sites when using the latest versions of the Firefox browser.

Next update by: Wednesday, April 13, 2022, 1:00 PM (3:00 AM UTC)
April 13, 2022 11:17 AM
We've identified that additional validation of the fix is required prior to deploying it to the impacted environments. We're deploying the fix to our testing environment to ensure it successfully resolves the underlying issue. We anticipate this internal validation will complete and the fix will be ready for deploying to the impacted users by our next communications update.

Next update by: Thursday, April 14, 2022, 5:30 AM (4/13/2022, 7:30 PM UTC)
Hello Bryce,

We have a same problem on our SharePoint Online but with only few users. they use a firefox 99

If you find a fix for this problem, can you give us the solution on this thread.

On our side, we are also trying to find a solution and come back to you if we find.

Thank you.

Hey @Flo_ENSI 


If a user is experiencing this issue, they only need to 'force' refresh the page in question. This means:

• Command-Shift-R (Mac OS X)

• Ctrl-F5 (Windows)


Hopefully this helps you and your users to continue using SharePoint while MS fix the issue.

Hi I have noticed the same behaviour at our site with our users that have automatically upgraded to Firefox version 99.0.1

The workaround that resolved the issue was to manually refresh Firefox. As per these instructions,

Make sure you back up your firefox saved passwords etc before running the refresh

Click the menu icon, then click on “Help”. ...
Click “More troubleshooting information”. ...
Click the “Refresh Firefox” button in the upper-right corner of the “Troubleshooting Information” page.
Confirm. ...
Click “Finish”.
best response confirmed by Bryce McMillan (Occasional Contributor)
Microsoft have updated and completed the fix to rectify this situation under service advisory SP357692. Fix and last update confirmed on Thursday, April 14, 2022, 2:00 AM (4/13/2022, 4:00 PM UTC).