Fun with Eclipse Browser Settings in IBM Notes

Just because we can, you can play around with some settings in IBM Notes on Windows.

Instead of using the Internet Explorer engine to render websites in Notes you can use XULrunner, the engine from the popular Firefox browser.

First check which engine Notes is currently using by opening a browser window within Notes (Open - Web), you may have to check your preferences to use the internal browser.
Go to https://www.whatismybrowser.com/

Now edit the file [notesprogramdir]/framework/rcp/plugin_customization.ini and add the two lines:
com.ibm.rcp.ui.browser/embeddedBrowser=Mozilla
com.ibm.rcp.rte/RTEBasedBrowser=XULRunner

Now close all browser windows and restart Notes.

Update, 5 October 2026

Checked again on HCL Notes 14.5.101 for Windows (notes.exe from 26 June 2026). Both lines are still honored. The client still ships XULRunner, now version 45.9.0. That is a rebuild of the Firefox 45 engine (platform.ini Milestone=45.9.0, BuildID=20251205101954). The Notes 14.5 release notes describe this upgrade from 43 to 45. HCL still uses that engine for a few embedded-browser tasks. The federated-login screen in 14.5 is Microsoft Edge, because XULRunner cannot run the JavaScript those login pages need.

embeddedBrowser=Mozilla still switches the in-client browser (Open - Web) from MSIE to the XULRunner service. Any value other than MSIE does that. Link clicks in mail and documents open the operating-system browser. That has been the case since Notes 9.0.1 FP9, and Preferences no longer offers a Web Browser choice. This line also leaves Notes federated login on Edge.

RTEBasedBrowser=XULRunner still switches HTML mail rendering on Windows to the XULRunner editor. On this 14.5.101 build the mail renderer otherwise still uses IE. An Edge renderer is already in the same build and is used when IE is disabled. Starting with Notes 14.5.1 FP1, HCL changed the HTML-mail default from IE to Edge after crashes while opening MIME mail (SPR ASIADP9HZ4). The notes.ini setting DisableOldBrowser=0 returns that default to IE.

The Eclipse SWT browser in this client implements IE and Edge (WebView2). These two preferences select Notes' own browser service and the mail renderer.

In 2013 the switch bought a newer engine than the Windows IE control, and the same engine Mac and Linux already used. That advantage is gone. Firefox 45 has no current CSS or JavaScript, and many sites refuse the TLS it can offer. For current mail and current websites, Edge is the better embedded engine, and links already open in the external browser.

The remaining reason to add the two lines is a single old HTML mail or internal page that renders in this Gecko 45 engine and fails in IE or Edge.