What does it mean when the form action attribute is "#" (number/pound symbol/sign/character)?

Question

What does it mean when the form action attribute is "#" (number/pound symbol/sign/character)?

What happens when a form input's formaction attribute is set to "#"? Does this prevent the input from being submitted to the server?

<form method="GET" action="example.php">
    <input type="text" size="20" name="text1" value="text1" formaction="#"/>
    <input type="text" size="20" name="text2" value="text2"/>
    <input type="submit" value="Submit"/>
</form>

Answer 1

The meaning of # as a URL reference (whether as action or formaction attribute value or otherwise) is a reference to the start of the current base document. The base document is the current document, unless a <base href=...> tag has been set.

What happens depends on the situation. Typically, the browser requests for the page again with a query part in the URL (and the page is loaded again, which may imply that client-side scripts are run), but if the same query had been used earlier, the browser probably uses its cache. Moreover, as the start of the document is referred to, focus on any form element is lost and the page may scroll backwards.

So although # is fairly common in some coding styles, it is not reliable; its purpose is better achieved using client-side event handlers.

The formaction attribute has a meaning only for submit buttons. A text input element does not constitute a submit button, even though it may trigger form submission, so here the attribute is ignored.