Which elements can be safely made contenteditable?

Question

I've been working with contenteditable recently within a HTML5 page and encountering bugs when using it with certain elements, and I'd like to know where and how I can actually safely use it.

I've discovered that making a span element contenteditable results in some buggy behaviour in both Firefox¹ and Chrome². However, making a div or section contenteditable appears completely safe³.

A guideline a couple of people have mentioned is that only block-level elements should be made contenteditable. However, the Mozilla Developer Network lists the heading elements h1 through to h6 as block-level elements, and making a heading element contenteditable is buggy in Firefox⁴ and can crash the page in Chrome⁵.

I'd like to be able to use more than just divs and sections, but I'm not clear on what elements I can actually safely make contenteditable. By safely, I mean that using the element under normal conditions, I should be able to perform normal editing tasks without it doing unexpected or buggy things. I should be able to write in it, delete content, cut, copy, paste, and move my text cursor about and highlight text without unexpected or strange behaviour.

So, which elements can I really make contenteditable safely? Is there a specific category? Are there certain criteria the safely-contenteditable element must match?

Bug notes:

1. Firefox 21 w/ span: Element loses focus if the text cursor is brought to the beginning or end of the element, but not if it got there by deleting content. Highlighting part of the element, cutting and then pasting will split the element in two at that point then insert a blank element between the two parts - without actually putting the text you were trying to paste anywhere.
2. Chrome 27 w/ span: If the span covers multiple lines e.g. by being wordwrapped, cutting and pasting content will often insert a linebreak after the pasted content.
3. Unless you make the div display:inline, in which case it can still lose focus as in 1, but apparently only if you bring the text cursor to the end. I don't consider this "normal" usage of the element though.
4. Firefox 21 w/ heading: Selecting part of the content then cutting and pasting will, similarly to 1, split the heading element in half at that point, and insert a third heading element between the two halves. It will, at least, have your pasted content inside it, but now you have three heading elements where there was originally one.
5. Chrome 27 w/ heading: Select some content and cut and paste. The page crashes. You get an "Aw snap!" message. That's it.

Demo code

Here's a demo for reproducing the above. It's pretty simple, though at the moment the only thing it isn't reproducing is the lose-focus bug.

Answer 1

In my opinion, I'd say div is the safest bet across the board. Any element you wish to truly edit (be it a span, header, etc), you can place inside the div and edit as if it were just that element. Also, to account for the display:inline issue you mentioned, you could always use float:left or float:right on your editable div to give it an "inline feel" without having it actually be inline.

Hope that helps!