Newer versions of HTML introduce features like the contenteditable="true" attribute (for example).

Can new HTML features be added to the supported HTML on Stack Exchange sites, or is the list of allowed HTML tags frozen.

The Wikimedia projects decided to ban dangerous HTML features as well as those which are not useful. Moreover, the wiki syntax is considered powerful enough. So it won't change even if useful features are found.

Is it the same policy in effect for Stack Exchange sites (with Markdown in place of wiki syntax)?

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    That's pretty vague.. do you have usage in mind of these features? Do you have a specific use case where it would be awesome? What do you mean by "in the supported Html of SE sites"? Commented Dec 3, 2013 at 21:49
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    Yeah, you need to be more specific. Any discussion about feature requests would have to focus on a specific feature and its potential benefits, not technology for the sake of technology.
    – user102937
    Commented Dec 3, 2013 at 21:56
  • Not at all. That's peoples told me on wikimeda: since there's no usage of those options, The php file responsible for the filter will not change unless there are bugs. So, I'm wondering if the list can change or there's no way to do proced even if a new usefull tag(for example) is found. Commented Dec 3, 2013 at 21:57
  • Sorry, but what exactly does Wikimedia have to do with anything? Stack Exchange doesn't run on Wikimedia and certainly not on PHP. What list are you talking about?
    – JJJ
    Commented Dec 3, 2013 at 21:59
  • @Juhana : This one. Commented Dec 3, 2013 at 22:00
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    What benefit would allowing contenteditable have?
    – JJJ
    Commented Dec 3, 2013 at 22:02
  • @Juhana : Really nothing! This was just an example... Commented Dec 3, 2013 at 22:11
  • @PeterMortensen : This question is definitely related to html with markdown. Please put the tag again (I can't do it since you removed it). Commented Dec 3, 2013 at 22:14
  • @TheGrinch : Does the question fit more the rules Now? You didn't waited my edits after your comment. Commented Dec 3, 2013 at 22:15
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    Ask a new question about a Stack exchange feature you want that is specific, actionable, and doesn't involve a hypothetical.
    – user102937
    Commented Dec 3, 2013 at 22:17
  • @TheGrinch : When wikimedia I got an answer in ~20 mins for this. If Stack Exchange have the same behaviour than on wikimedia, it mean asking for support for new HTML features is completely useless... Detemining this make this question usefull... Commented Dec 3, 2013 at 22:25
  • An answer in 18 minutes for what, specifically?
    – user102937
    Commented Dec 3, 2013 at 22:26
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    [sigh] Stack Exchange is not written in PHP.
    – user102937
    Commented Dec 3, 2013 at 22:32
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    The simple answer is: of course the list can be changed, if there is a very, very good reason for it. You'll also have to understand that this is not Wikipedia and not as far community-driven. Wikimedia is open source, SE engine is proprietary, and the dev team can do whatever changes they want. If there's a reason for it.
    – JJJ
    Commented Dec 4, 2013 at 6:22
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    That is what I disagree about. `code` is for code, and contenteditable="true" is all code. Also, following your logic, you should also have excluded the = from that formatting then.
    – Arjan
    Commented Dec 4, 2013 at 18:39

1 Answer 1


The set of allowed HTML tags and attributes is frozen. There would need to be a very, very good reason to allow additional tags and attributes, as doing so would tend to increase the chance of malformed or malicious code breaking something and would very likely also require styling changes across all sites.

If you think you have a very, very good reason, post a [feature-request] - just be aware, you're starting with an implicit score of -100.

Note that the Markdown engines used here are open source - so you're free to allow whatever HTML you want on the sites that you build yourself.

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    I'm already starting with a score of -5 by just talking about it! I easy imagine what a feature-request would does! Also this involve the same result as on Wikipedia: you are steel free to edit sanitizer.php on your site... Commented Dec 4, 2013 at 18:27
  • But this might change as I found a way to use arbitrary ʜᴛᴍʟ and ᴄꜱꜱ. but it can’t be used for running JavaScript. Commented Sep 8, 2015 at 18:45
  • @user2284570: there's no sanitizer.php on this site. And allowing some features is not just removing some restriction. It requires the developers to test and verify that absolutely everything on the site works fine and securely. It's not an easy task and it would take a lot of time and money. Commented Sep 13, 2015 at 19:39

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