IE Compat Bridge

IE-era JavaScript compatibility

Fix IE-era JavaScript errors in Chrome

Errors around attachEvent, window.event, event.srcElement, showModalDialog, and document.frames usually mean an old page expects Internet Explorer-era browser behavior. The right fix depends on whether the page needs the IE engine or only a scoped JavaScript and DOM bridge.

Signals that can be patched

  • attachEvent handlers on old forms, menu bars, or picker dialogs.
  • Code that reads window.event, event.srcElement, returnValue, or cancelBubble.
  • Picker windows built around showModalDialog return values.
  • Old frameset or iframe access through document.frames.
  • WebForms controls where the generated HTML works but legacy event binding fails.

Signals that need IE mode

  • ActiveX controls, COM objects, Browser Helper Objects, or Windows-only plug-ins.
  • VBScript or Trident/MSHTML rendering dependencies.
  • Strict IE document modes or Enterprise Mode site-list requirements.
  • Pages that intentionally block non-IE engines before serving normal HTML.

Recommended triage path

  1. Open the page in Chrome and capture the first failing action, not just the first console error.
  2. Check whether the broken feature is ordinary JavaScript/DOM behavior or a native IE engine dependency.
  3. If it is native IE technology, use Microsoft Edge IE mode or another managed legacy-browser path.
  4. If it is JavaScript/DOM compatibility, try one authorized hostname with IE Compat Bridge before expanding.
  5. Keep the test narrow: one page, one workflow, one configured origin, and no secrets in screenshots or diagnostics.
Install from Chrome Web Store Read the WebForms guide

Why source changes are still best

If you maintain the application, update the JavaScript directly. Feature-test the method you need, move from attachEvent to addEventListener, replace synchronous modal assumptions, and remove IE-only branches over time.

When a bridge is useful

A bridge is useful when the application cannot be changed quickly, the page already mostly works in Chromium, and the organization wants a contained trial before deciding whether full IE mode is required.

IE Compat Bridge boundary

IE Compat Bridge applies scoped JavaScript and DOM compatibility fixes only on configured and authorized domains. It is not an Internet Explorer emulator and does not run ActiveX, COM, VBScript, Trident, Java applets, or true IE document modes.