The best replacement for contenteditable is textarea.

The best alternatives to contenteditable are rated as following:
★★★★★  textarea
★★★  designmode

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Speaking about contenteditable, one probably shouldn't forget about wysiwyg.

Other search terms related to contenteditable and their ratings are:
★★★★★ wysiwyg
You have in mind a companion for contenteditable and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of contenteditable in all years. Click on graph for more.
contenteditable
textarea
designmode