[Solved] JS errors in RadHtmlChart

[Fit2Page]

I have a page with multiple RadHtmlCharts onit which generates following errors:

 

Telerik.Web.UI.WebRe…43f6d9%3aed16cbdc:6[Violation] Permissions policy violation: unload is not allowed in this document.

	Sys.UI.DomEvent.addHandler	@	Telerik.Web.UI.WebRe…43f6d9%3aed16cbdc:6
	(anoniem)	@	Telerik.Web.UI.WebRe…43f6d9%3aed16cbdc:6
	(anoniem)	@	Telerik.Web.UI.WebRe…43f6d9%3aed16cbdc:6

 

Do you have any idea what could cause this?

I guess this is blocking other Javascripts on the page.

[Fit2Page]

Now I see that these errors are generated on ALL pages in the application, not specifically to do with RadHtml Charts then.

[Vasko]

Hi Marc,

Thank you for reaching out and for sharing the screenshot. The error you're seeing  "[Violation] Permissions policy violation: unload is not allowed in this document"  is a known issue that does not originate from Telerik UI for ASP.NET AJAX. It stems from the ASP.NET WebForms framework itself, specifically the Microsoft AJAX scripts (MicrosoftAjax.js / MicrosoftAjaxWebForms.js).

We have an official KB article on this topic: Resolve Deprecated Unload Event Listeners.

Why is this happening?

Chrome has deprecated the unload event listener as an intended API change. The Microsoft AJAX scripts register unload event handlers (as visible in your stack trace: Sys.UI.DomEvent.addHandler → Sys.WebForms.PageRequestManager._initialize), which trigger this console violation. This is reproducible even on a bare-bones WebForms page with just a ScriptManager and a Button — no Telerik controls required.

Will this break my application?

Both Daniel Roth (Principal Product Manager, ASP.NET at Microsoft) and Barry Pollard (Web Performance Developer Advocate, Google Chrome) have confirmed that the deprecation of the unload event will not cause errors — the event will simply stop firing. Since it has already been unreliable in modern web scenarios, this should not have a major functional impact.

• Daniel Roth's statement: Microsoft Developer Community
• Barry Pollard's confirmation: Tweet

The console warnings cannot be suppressed programmatically — they are browser-level messages for developers and are non-critical.

How you can help push for a resolution

Since this issue must be fixed by Microsoft in their ASP.NET AJAX framework scripts, we strongly encourage you to vote and comment on the following Microsoft Developer Community reports. The more voices Microsoft hears, the higher the priority for a fix:

1. Unload event listeners are deprecated (original report)
2. ASP.NET WebForms ScriptManager triggers Permissions Policy violation (new report)

Your vote and feedback directly influence Microsoft's prioritization. Since Microsoft continues to support .NET Framework 4.8.1 with security fixes until at least 2029, it's important they address this compatibility issue in their framework scripts.

We're here to help please share additional details about the functional issues you're encountering and we'll investigate further.

Regards,
Vasko
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