Dear colleagues,

Microsoft Edge is gradually retiring default support for the web platform unload event. This may affect websites and web applications that rely on unload event handlers.

If your websites or applications do not use unload event handlers, no action is required.

Action required

By September 5, 2026:

Website and application owners should:

• • Identify and test websites and applications that use unload event handlers, including through third-party libraries.
  • Update affected applications to use supported alternatives.
  • If an application cannot be updated immediately, review Microsoft’s temporary options for maintaining unload support during the transition.

Microsoft is gradually introducing this change from Microsoft Edge 152 through Edge 155.

Resources:

• • Read Microsoft announcement
  • Review Microsoft Edge policy

Local IT teams: Please share this information with website and application owners and developers in your division or unit.

If you have any further questions or concerns, please submit a ticket to the Enterprise Service Centre at (https://uoft.me/m365help).

Kind regards,

Enterprise Applications & Solutions Integration (EASI)
Information Technology Services, University of Toronto