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CKSource Graded Browser Support

Starting from the next CKEditor and CKFinder releases, we will be managing browser compatibility support of our projects in a different and modern way. After some consideration, we have decided to use the YUI Graded Browser Support (also known as “GBS”) as the basis for our products. We will, however, add a few exceptions to the YUI GBS model that we feel are important for our user base.

YUI Graded Browser Support is an approach to progressive enhancement proposed by Yahoo!. Detailed information about this initiative can be found on its dedicated page, including the reasoning behind their choices.

From now on, not only do we intend to provide a similar browser support that YUI GBS proposes, but we will also incorporate their culture and behavior regarding the grades of support and our QA approach to them.

CKSource A-Graded Browser Support

The following is the list of browser versions that will receive A-grade support as defined by the CKSource GBS. All CKSource projects, including CKEditor and CKFinder, aim to provide at least full A-grade support for the following products:

  • Internet Explorer: 6.0, 7.0, 8.0, 8.0 Quirks and 9.0
  • Firefox: all major stable releases starting from 3.† (e.g. 4.†, 5.†, etc.)
  • Safari: 5.†
  • Chrome: latest stable
  • Opera: latest stable

Cursive terms indicate our additions to the YUI GBS. The dagger symbol (†) indicates that the most current non-beta version at that branch level receives support.

All browsers are to be supported for web pages with the Document Type Declaration (doctype) of XHTML 1.0 Transitional except for IE 8 Quirks, which will support unknown doctypes.

X-Graded Browsers

We will follow the YUI GBS approach for X-graded browsers. This group encompasses rare, experimental, or unknown browsers that are assumed to be compatible and modern. QA does not test, and bugs are not opened, against X-graded browsers.

Our X-graded browsers list is different than the YUI one though. It includes the following browsers, except those already included in the A-grade list:

  • Browsers based on the Gecko engine version >= 1.9.0 (Firefox 3.0).
  • Browsers based on the WebKit engine version >= 522 (Safari 3).
  • Opera version >= 9.5.

Accessibility Support

Besides the browser support described above we are also introducing the following table to define the list of browsers and assistive technologies supported by our products.

  Win 7 + JAWS †.† Win XP High Contrast
Firefox 4.† A-grade A-grade
Internet Explorer 8   A-grade


Accessibility is just making its first steps into the Web environment. The support for accessibility in browsers and assistive technologies is still very inadequate. In response to this the WAI-ARIA standard was created, aiming to solve this situation. Its adoption is still quite limited, though, and the only browser with good enough support for it at the moment is Firefox.

Internet Explorer

Internet Explorer 8 is the first version to start offering support for WAI-ARIA. It is still not complete, but the partial support it introduces looks promising. Even if we do not officially support this browser with regard to accessibility, we are still taking it in consideration during our development, testing it, and eventually working around its limitations. Currently CKEditor should provide a good experience for Internet Explorer 8 users that need accessibility support. In any case, we still strongly recommend to use Firefox for an optimum accessibility experience.

A Word About Mobile Environments

Right now we are working on introducing iOS 5 (iPhone and iPad) support to CKEditor. As a result, we may in due course enlarge our graded support to also include iOS.

We are continuously watching the fast growing mobile market in order to find opportunities to integrate our products with a wider range of devices. We hope to have more news regarding this in the near future.

IE6 and IE Quirks

At the moment we are considering whether to support IE 6 and IE Quirks mode in the future (read CKEditor 4). These browsers are simply too limited for the needs of modern web applications, forcing the CKEditor standards down instead of helping us innovating.

It would be great to hear from our community about your expectations on having an editor that works with these old browsers versus having a more advanced and modern editor instead.


We hope this change will represent a step forward for the quality of our projects. Our intention is to propose clear expectations for our community regarding the level of support one can find in our software.

We are updating our documentation with the new support tables. That page will be reviewed following changes to the YUI GBS as well as changes on the browser market.

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