Is it a good practice to use an empty URL for a HTML form's action attribute? (action=“”)

Question

I am wondering if anyone can give a "best practices" response to using blank HTML form actions to post back to the current page.

There is a post asking what a blank HTML form action does here and some pages like this one suggest it is fine but I'd like to know what people think.

Answer 1

The best thing you can do is leave out the action attribute altogether. If you leave it out, the form will be submitted to the document's address, i.e. the same page.

It is also possible to leave it empty, and any browser implementing HTML's form submission algorithm will treat it as equivalent to the document's address, which it does mainly because that's how browsers currently work:

8. Let action be the submitter element's action.

9. If action is the empty string, let action be the document's address.

Note: This step is a willful violation of RFC 3986, which would require base URL processing here. This violation is motivated by a desire for compatibility with legacy content. [RFC3986]

This definitely works in all current browsers, but may not work as expected in some older browsers ("browsers do weird things with an empty action="" attribute"), which is why the spec strongly discourages authors from leaving it empty:

The action and formaction content attributes, if specified, must have a value that is a valid non-empty URL potentially surrounded by spaces.

Answer 2

Actually, the Form Submission subsection of the current HTML5 draft does not allow action="". It is against the spec.

The action and formaction content attributes, if specified, must have a value that is a valid non-empty URL potentially surrounded by spaces. (emphasis added)

The quoted section in mercator's answer is a requirement on implementations, not authors. Authors must follow the author requirements. To quote How to read this specification:

In particular, there are conformance requirements that apply to producers, for example authors and the documents they create, and there are conformance requirements that apply to consumers, for example Web browsers. They can be distinguished by what they are requiring: a requirement on a producer states what is allowed, while a requirement on a consumer states how software is to act.

The change from HTML4—which did allow an empty URL—was made because “browsers do weird things with an empty action="" attribute”. Considering the reason for the change, its probably best not to do that in HTML4 either.

Answer 3

Not including the action attribute opens the page up to iframe clickjacking attacks, which involve a few simple steps:

• An attacker wraps your page in an iframe
• The iframe URL includes a query param with the same name as a form field
• When the form is submitted, the query value is inserted into the database
• The user's identifying information (email, address, etc) has been compromised

References

• Bypassing CSRF protections with ClickJacking and HTTP Parameter Pollution

Answer 4

This will validate with HTML5.

<form action="#">

Answer 5

IN HTML 5 action="" IS NOT SUPPORTED SO DON'T DO THIS. BAD PRACTICE.

If instead you completely negate action altogether it will submit to the same page by default, I believe this is the best practice:

<form>This will submit to the current page</form>

If you are sumbitting the form using php you may want to consider the following. read more about it here.

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">

Alternatively you could use # bear in mind though that this will act like an anchor and scroll to the top of the page.

<form action="#">

Answer 6

I think it's best to explicitly state where the form posts. If you want to be totally safe, enter the same URL the form is on in the action attribute if you want it to submit back to itself. Although mainstream browsers evaluate "" to the same page, you can't guarantee that non-mainstream browsers will.

And of course, the entire URL including GET data like Juddling points out.

Answer 7

Just use

?

<form action="?" method="post" enctype="multipart/form-data" name="myForm" id="myForm">

It doesn't violate HTML5 standards.

Answer 8

I used to do this a lot when I worked with Classic ASP. Usually I used it when server-side validation was needed of some sort for the input (before the days of AJAX). The main draw back I see is that it doesn't separate programming logic from the presentation, at the file level.

Answer 9

I use to do not specify action attribute at all. It is actually how my framework is designed all pages get submitted back exact to same address. But today I discovered problem. Sometimes I borrow action attribute value to make some background call (I guess some people name them AJAX). So I found that IE keeps action attribute value as empty if action attribute wasn't specified. It is a bit odd in my understanding, since if no action attribute specified, the JavaScript counterpart has to be at least undefined. Anyway, my point is before you choose best practice you need to understand more context, like will you use the attribute in JavaScript or not.

Answer 10

When you put empty action then some security filtration consider it malicious or phishing. Hence they can block your page. So its advisable not to keep action= blank.