Browsers Compatibility

This website contains links to software which is either no longer maintained or will be supported only until the end of 2019 (CKFinder 2). For the latest documentation about current CKSource projects, including software like CKEditor 4/CKEditor 5, CKFinder 3, Cloud Services, Letters, Accessibility Checker, please visit the new documentation website.

If you look for an information about very old versions of CKEditor, FCKeditor and CKFinder check also the CKEditor forum, which was closed in 2015. If not, please head to StackOverflow for support.


Officially Supported Browsers

Officially, we'll be declaring support for the following browsers:

  • Internet Explorer 6+
  • Firefox 2+
  • Safari 3+
  • Opera 9.5+

It means that the above browsers and their successors will be part of our everyday coding activities. All features must work properly with all of them, and their users must have a wonderful and usable experience, with no surprises. It means also that no strange code will be included in the core to provide compatibility with other browsers.

Engine Compatible Browsers

Browsers based on the rendering/runtime engines used by the above browsers will certainly benefit compatibility. We are not listing those browsers here because it would be too hard to put all those browsers lines at test while coding. We instead invite all browsers vendors and communities to participate, creating specific browser testing groups. Tickets for those browsers are welcome, and we'll work on them whenever possible.

Notable Exclusions

  • Internet Explorer 5.5: This browser is too old and too limited. There is a silly possibility of making it compatible, but we'll not go crazy because of it.
  • Firefox 1.5 and before: Fortunately Firefox users are usually well updated. Considering that Firefox 3 is to be released this year, and that Mozilla will discontinue supporting their 1.x series, we can definitely drop support for it, removing yet another browser version from being tested in the development line.
  • Safari 2.x: The editing support in this browser is still too limited. There are many other features also missing on it (like proper Range manipulation) which would force us to make the code too dirty and much probably provide a buggy and bad user experience.
  • Opera 9.2x: Just like Safari 2.x, with the same argumentation.
  • Netscape: this browser has been discontinued by AOL, so it is destined to die. In any case Netscape 9 is based on Gecko 1.8.1, just like Firefox 2. So, it will much probably fell down in the "Engine Compatible Browsers' group.
  • Konqueror: it has no editing support. There are rumors that they will be moving to WebKit, which could open compatibility possibly. It would join the "Engine Compatible Browsers" in that case.


We'll be constantly testing our code over Beta versions for our officially supported browsers. In this way we may try to advise browser vendors about possible issues, or at least work to fix it our side.

This page was last edited on 7 February 2008, at 18:38.