When a rich text field's Web Access: Display property is marked "Best Fit For OS", the web server selects one of the HTML editors based on the browser.
The Java Editor Applet is used for all browsers but Internet Explorer (IE).
For Internet Explorer a combination of IE version and OS version (of the clinet) is used to choose the Applet (very old IE), the DHTML control or the (dojo) JavaScript editor. (The latter for Vista and beyond, because the DHTML control is not available)
As of 8.5.1 FP1 the
domino-data-directory/browser.cnf file can be used to control the Best Fit For OS.
Look at the file for the "RTEditorBestFit" property. There is a comment in the file explaining its use.
As an example, suppose you want to use the same editor (the dojo JavaScript control) for all modern browsers.
Put the following in browser.cnf
Property RTEditorBestFit String Legacy
Rule JSControl MSIE [6-9].* Windows NT [6-9]
Rule JSControl Firefox/[3-9]
Rule JSControl Version/[3-9][0-9\.]* Safari
Rule JSControl Chrome/[2-9]
Rule JSControl Opera/[7-9]
Note: you should make a backup copy of the browser.cnf file, in case it is overwritten when you upgrade to a new domino server version.
See also
Extending Dojo Rich Text Editor's Toolbar.