Issue
Google and Microsoft are jointly retiring the legacy unload event in Chromium-based browsers. Chrome began a staged, percentage-based rollout in March 2025 and reaches 100% of all Chrome page loads on Chrome 154 (September 22, 2026). For details see Deprecating the unload event.
Microsoft Edge (also Chromium-based) is retiring default unload support on the same general timeframe, beginning September 2026. For details see Force Permission Policy Unload Default Enabled.
Symptoms and Impact
No end-user impact has been reported so far. In some cases, the following browser console message may appear: "[Violation] Permissions policy violation: unload is not allowed in this document."
However, some users have reported that Tracer cannot be relaunched within the same session after the initial Tracer window is closed, as the unload event does not properly release the active tracer session. This leaves the requestor blocked and requires the user to log out and log back in or manually terminate the Tracer session.
If additional symptoms are identified, this document will be updated.
Solution
| Pega Platform Version | Hotfix |
| 23.1.0 |
HFIX-D3450
|
| 23.1.1 | HFIX-D3451 |
| 23.1.2 | HFIX-D3452 |
| 23.1.3 | HFIX-D3453 |
| 23.1.4 | HFIX-D3861 |
| 23.1.5 | HFIX-D3425 |
| 24.1.0 | HFIX-D3445 |
| 24.1.1 | HFIX-D3446 |
| 24.1.2 | HFIX-D3867 |
| 24.1.3 | HFIX-D3862 |
| 24.1.4 | HFIX-D3449 |
| 24.1.5 | HFIX-D3863 |
| 24.2.0 | HFIX-D3444 |
| 24.2.1 | HFIX-D3443 |
| 24.2.2 | HFIX-D3442 |
| 24.2.3 | HFIX-D3441 |
| 24.2.4 | HFIX-D3430 |
| 24.2.5 | HFIX-D3422 |
| 25.1.0 | HFIX-D3426 |
| 25.1.1 | HFIX-D3864 |
| 25.1.2 | HFIX-D3428 |
| 25.1.3 | HFIX-D3421 |
| 25.1.4 | HFIX-D3944 |
| 26.1.0 | HFIX-D3865 |
| 26.1.1 | HFIX-D3866 |
For clients running out-of-support versions, please disable the "Deprecate the unload event" flag in your browser settings to mitigate unload-related issues when an immediate upgrade to a supported version is not feasible. However, upgrading to a supported release version remains the recommended path for resolution.
Solution for clients using Constellation
If you are using Constellation on 25.1.1, 25.1.2 or 25.1.3 release, raise an incident with Global Client Support in My Support Portal, to obtain an additional hotfix.
Additional guidance:
- To control access to the unload event, refer to the Chromium guidance here: Control access to unload.
- If your custom code uses unload events, refer to the Chromium guidance for recommended alternatives: Alternatives to unload events.
- Based on currently available information, this unload event deprecation applies only to Chromium-based browsers.
References
- Deprecating the unload event
- Force Permission Policy Unload Default Enabled
- Control access to unload
- Alternatives to unload events
If you have any questions or concerns, create a support request with Global Client Support in My Support Portal.