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Asked: 2026-06-05T00:30:12+00:00

Or maybe you call it "sharp" – the # symbol. I’ve came across one

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Or maybe you call it "sharp" – the # symbol.

I’ve came across one instance, where #! and # used simultaneously in a single URL. From reading other articles, including RFC, I can’t understand whether that is a legal combination or not. When encountering such page Mozilla browser (Iceweasel in this case) displays the URL as having 2 #’s, while Chrome displays only one, but dies shortly afterwards (the tab containing the page becomes unresponsive and crashes – but it may not be connected).

Now, my question is, is it legal to have both in one URL, is it maybe legal and redundant (should be normalized), or is it just a bug in Mozilla browser? So, suppose I’m making an AJAX request, or trying to navigate the browser history – what should I do, if I encounter this situation?

double hash in url

RFC-3986: https://www.rfc-editor.org/rfc/rfc3986#section-3.4 , which should be clarifying it… just in case.

Also: https://developers.google.com/webmasters/ajax-crawling/docs/specification how Google crawlers see things.

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1 Answer

  1. Editorial Team

    The format for a fragment only allows slashes, question marks, and pchars. If you look up the RFC, you’ll see that the hash mark is not a valid pchar.

    However, browsers will try their best to read non-valid URLs by treating repeat hashes as though they are escaped, as you can see by checking the value of window.location.hash (in IE, Firefox, and Chrome) for

    http://www.example.com/hey#foo#bar

    which is the same window.location.hash for

    http://www.example.com/hey#foo%23bar
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