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[Problem/Bug]: WebView2 Runtime 156.x prevents New Outlook attachments from opening, Fixed Runtime 155.0.4283.62 works #5782
Description
What happened?
After Microsoft Edge WebView2 Runtime was updated to the 156.x branch, attachments in New Outlook for Windows stopped opening.
We have reproduced the issue on multiple machines.
Affected configurations observed:
WebView2 Runtime 156.0.4314.42 -> attachments do not open
WebView2 Runtime 156.0.4314.50 -> attachments do not open
We performed an A/B test on an affected machine without uninstalling or replacing the Evergreen WebView2 Runtime.
We downloaded Microsoft.WebView2.FixedVersionRuntime.155.0.4283.62.x64 and configured New Outlook (olk.exe) to use it through the WebView2 BrowserExecutableFolder policy.
After restarting New Outlook, Settings > General > About Outlook confirmed:
Microsoft Outlook Version: 1.2026.1013.100
Client Version: 20261016004.16
WebView2 Version: 155.0.4283.62 (Stable)
Without making any other changes, the same attachment that failed to open with WebView2 156.x opened successfully with WebView2 155.0.4283.62.
Returning New Outlook to WebView2 156.x reproduces the attachment-opening problem.
This appears to be a regression introduced in the WebView2 Runtime 156.x branch affecting New Outlook attachment handling.
Importance
Important. My app's user experience is significantly compromised.
Runtime Channel
Stable release (WebView2 Runtime)
Runtime Version
156.0.4314.42, 156.0.4314.50 and Last working version 155.0.4283.62
SDK Version
N/A - issue occurs in Microsoft New Outlook for Windows
Framework
Win32
Operating System
Windows 11
OS Version
Windows 11 26H2 (26300.9711)
Repro steps
-
Install/use New Outlook for Windows version 1.2026.1013.100 (x64), Client Version 20261016004.16.
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Run New Outlook with Microsoft Edge WebView2 Runtime 156.0.4314.42 or 156.0.4314.50.
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Open an email containing an attachment.
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Attempt to open the attachment.
-
Observe that the attachment does not open.
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Download and extract Microsoft.WebView2.FixedVersionRuntime.155.0.4283.62.x64.
-
Configure only olk.exe to use the Fixed Runtime through:
HKLM\SOFTWARE\Policies\Microsoft\Edge\WebView2\BrowserExecutableFolder
Value name:
olk.exe
Value:
C:\Temp\WebView2\Microsoft.WebView2.FixedVersionRuntime.155.0.4283.62.x64
-
Restart New Outlook.
-
Verify in Settings > General > About Outlook that WebView2 Version is now 155.0.4283.62 (Stable).
-
Open the same email and the same attachment.
Expected:
The attachment opens.
Actual results:
WebView2 156.0.4314.42 -> FAIL
WebView2 156.0.4314.50 -> FAIL
WebView2 155.0.4283.62 -> PASS
Repros in Edge Browser
No, issue does not reproduce in the corresponding Edge version
Regression
Regression in newer Runtime
Last working version (if regression)
155.0.4283.62
Activity
ojasvi1450 commentedon Oct 28, 2026
Hi johnandersson80-debug,
We tried reproducing this locally with WebView2 Runtime
156.0.4314.50and New Outlook1.2026.1022.100, and attachments (including images and Excel.xlsxfiles) opened as expected on our end.To help us narrow down what might be triggering the failure in your environment, could you please share a few additional details?
.pdf,.msg/.eml,.docx,.zip, etc.)? We tested with images and Excel files which worked fine.1.2026.1022.100whereas your report shows1.2026.1013.100. Does updating New Outlook to the latest version resolve the issue on WebView2156.0.4314.50?If possible, could you share some logs/traces using this - https://github.com/MicrosoftEdge/WebView2Feedback/blob/main/diagnostics/etw.md
jacobwiggsFIT commentedon Oct 28, 2026
I have been seeing the same issue, though with only 2 users inside of our environment. Another note to help you guys troubleshoot, this is specifically when opening in Desktop apps. I copied over my Microsoft Support Request below with the information I currently have.
The expected flow it as follows:
User receives email with file attached > User previews file, or right clicks on the file > User selects the option to open the file in the Desktop version of an app (Adobe, Excel, Word, etc. same issue across all) > App opens the file
Instead of this, though, we are receiving the following flow:
User receives email with file attached > User previews file, or right clicks on the file > User selects the option to open the file in the Desktop version of an app (Adobe, Excel, Word, etc. same issue across all) > Outlook does 1 of 2 things, depending on the exact method used to try to open the file:
It brings up an error stating something along the lines of "Can't open file, please restart Outlook and try again"
It says "Opening file..." on a loading bar at the bottom, then the bar disappears.
After both of these, the file never opens.
I have this issue happening with 2 different users. The one user I am currently able to get the information from has an Outlook Version section as follows:
Microsoft Outlook Version: 1.2026.1013.100
Client Version: 20261016004.16
WebView2 Version: 156.0.4314.50 (Stable)
And has an Office build of:
16.0.20527.20088
For this User, I have also included logs from the Procmon application which I ran filtering for excel.exe and olk.exe. I verified with our SOC team that there are no blocks happening from our EDR application. I also verified that the files can be opened if downloaded, if using the the "Open in Excel (Web App)" option, and if using old Outlook. It appears to be linked specifically to the integration between New Outlook and desktop apps (both Microsoft, and Third Party, as PDFs won't open in Acrobat as briefly noted above.
Logfile.CSV
I will also add, that I do not have the issue on my personal company device, which has the same Outlook version, but an older WebView2 Version, specifically I have:
Microsoft Outlook Version: 1.2026.1013.100
Client Version: 20261016004.16
WebView2 Version: 155.0.4283.62 (Stable)
ojasvi1450 commentedon Oct 29, 2026
Hi, we were able to root cause and rollout a fix for this in the current stable. It should get fixed in the next 6-7 hours after a re-launch.
cristianpopescu2026-blip commentedon Oct 29, 2026
I have the same issue on 5 laptops, attachments won't open in preview
roxorbeton commentedon Oct 29, 2026
unknown2809 (@cristianpopescu2026-blip) Check the reply before you from ojasvi1450:
jstrate-blip commentedon Oct 29, 2026
Thank you for the update and the pending fix.
How is the WebView2 patch/updates rolled out? Is this done through the Edge updater, Office updater or Windows system updates?
ojasvi1450 commentedon Oct 29, 2026
A runtime update is done through the Edge Updater. This one was a kill switch on the same runtime which is deployed differently.
jstrate-blip commentedon Oct 29, 2026
Thank you for your updates!
ednabisco commentedon Oct 29, 2026
I have found an easy (perhaps temporary) solution for PDFs not opening/no "Open" option in the preview for the New Outlook. This may not work for other file types. I was only seeing this on PDF files; Word files were still opening for me.
In File Explorer, navigate to:
C:\Program Files (x86)\Microsoft\EdgeWebView\Application\156.0.4314.50\PdfPreview
Note: you may be using a different version of WebView2, so open the latest folder version.
Delete or rename the file: PdfPreviewHandler.dll
You will likely need to restart the computer.
I found that if I opened Outlook right away, it still wouldn't open PDFs for a minute, but then it did work.
I am not sure how long this fix will work. It may break again after a WebView2 update.
Perhaps it will be fixed in the next WebView2 update.
I have only tested this on 3 computers.
Hopefully users will find this works for them as well.
Good luck.
jacobwiggsFIT commentedon Oct 30, 2026
Just wanted to report back that the two users in our environment who had this problem have reported that it is now working. Thank you folks for taking care of this.
ojasvi1450 commentedon Oct 30, 2026
Marking this issue as closed.
roxorbeton commentedon Nov 2, 2026
What version do you have now? The latest we got, on multiple machines, was 156.0.4314.58 and it doesn't work.
JetmiRR commentedon Nov 2, 2026
This issue is still ongoing, do we have a fix?
Adnil01 commentedon Nov 2, 2026
Have you tried doing the runtime update via Microsoft Edge?
In my environment, I had to manually do it per affected users.
roxorbeton commentedon Nov 3, 2026
I you mean make Edge check for updates, yes. I did on multiple managed/unmanaged machines, also tried Edge update sheduled task. The newest version for me is 156.0.4314.58, which is also the latest minor version i see on release notes website, still have the problem
cristianpopescu2026-blip commentedon Nov 3, 2026
Confirm this problem. I have the same issue on 5 laptops, attachments won't open in preview
DWAA1660 commentedon Nov 4, 2026
Has anyone found the fix it still seems to be an issue.
jsip-100 commentedon Nov 4, 2026
I'm experiencing these issues on this exact version currently.
cxuOSU commentedon Nov 4, 2026
This is still an issue for me with WebView2 version 156.0.4314.58