How is the default submit button on an HTML form determined?

If a form is submitted but not by any specific button, such as

  • by pressing Enter
  • using HTMLFormElement.submit() in JS

how is a browser supposed to determine which of multiple submit buttons, if any, to use as the one pressed?

This is significant on two levels:

  • calling an onclick event handler attached to a submit button
  • the data sent back to the web server

My experiments so far have shown that:

  • when pressing Enter, Firefox, Opera and Safari use the first submit button in the form
  • when pressing Enter, IE uses either the first submit button or none at all depending on conditions I haven't been able to figure out
  • all these browsers use none at all for a JS submit

What does the standard say?

If it would help, here's my test code (the PHP is relevant only to my method of testing, not to my question itself)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
                      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Test</title>
</head>

<body>

<h1>Get</h1>
<dl>
<?php foreach ($_GET as $k => $v) echo "<dt>$k</dt><dd>$v</dd>"; ?>
</dl>

<h1>Post</h1>
<dl>
<?php foreach ($_POST as $k => $v) echo "<dt>$k</dt><dd>$v</dd>"; ?>
</dl>

<form name="theForm" method="<?php echo isset($_GET['method']) ? $_GET['method'] : 'get'; ?>" action="<?php echo $_SERVER['SCRIPT_NAME']; ?>">
    <input type="text" name="method" />
    <input type="submit" name="action" value="Button 1" onclick="alert('Button 1'); return true" />
    <input type="text" name="stuff" />
    <input type="submit" name="action" value="Button 2" onclick="alert('Button 2'); return true" />
    <input type="button" value="submit" onclick="document.theForm.submit();" />
</form>

</body></html>

Answers:

Answer

If you submit the form via Javascript (i.e. formElement.submit() or anything equivalent), then none of the submit buttons are considered successful and none of their values are included in the submitted data. (Note that if you submit the form by using submitElement.click() then the submit that you had a reference to is considered active; this doesn't really fall under the remit of your question since here the submit button is unambiguous but I thought I'd include it for people who read the first part and wonder how to make a submit button successful via JS form submission. Of course, the form's onsubmit handlers will still fire this way whereas they wouldn't via form.submit() so that's another kettle of fish...)

If the form is submitted by hitting Enter while in a non-textarea field, then it's actually down to the user agent to decide what it wants here. The specs don't say anything about submitting a form using the enter key while in a text entry field (if you tab to a button and activate it using space or whatever, then there's no problem as that specific submit button is unambiguously used). All it says is that a form must be submitted when a submit button is activated, it's not even a requirement that hitting enter in e.g. a text input will submit the form.

I believe that Internet Explorer chooses the submit button that appears first in the source; I have a feeling that Firefox and Opera choose the button with the lowest tabindex, falling back to the first defined if nothing else is defined. There's also some complications regarding whether the submits have a non-default value attribute IIRC.

The point to take away is that there is no defined standard for what happens here and it's entirely at the whim of the browser - so as far as possible in whatever you're doing, try to avoid relying on any particular behaviour. If you really must know, you can probably find out the behaviour of the various browser versions but when I investigated this a while back there were some quite convoluted conditions (which of course are subject to change with new browser versions) and I'd advise you to avoid it if possible!

Answer

Andrezj's pretty much got it nailed... but here's an easy cross-browser solution.

Take a form like this:

<form>
    <input/>
    <button type="submit" value="some non-default action"/>
    <button type="submit" value="another non-default action"/>
    <button type="submit" value="yet another non-default action"/>

    <button type="submit" value="default action"/>
</form>

and refactor to this:

<form>
    <input/>

    <button style="overflow: visible !important; height: 0 !important; width: 0 !important; margin: 0 !important; border: 0 !important; padding: 0 !important; display: block !important;" type="submit" value="default action"/>

    <button type="submit" value="some non-default action"/>
    <button type="submit" value="another non-default action"/>
    <button type="submit" value="yet another non-default action"/>
    <button type="submit" value="still another non-default action"/>

    <button type="submit" value="default action"/>
</form>

Since the W3C spec indicates multiple submit buttons are valid, but omits guidance as to how the user-agent should handle them, the browser manufacturers are left to implement as they see fit. I've found they'll either submit the first submit button in the form, or submit the next submit button after the form field that currently has focus.

Unfortunately, simply adding a style of display: none; won't work because the W3C spec indicates any hidden element should be excluded from user interactions. So hide it in plain sight instead!

Above is an example of the solution I ended up putting into production. Hitting the enter key triggers the default form submission is behavior as expected, even when other non-default values are present and precede the default submit button in the DOM. Bonus for mouse/keyboard interaction with explicit user inputs while avoiding javascript handlers.

Note: tabbing through the form will not display focus for any visual element yet will still cause the invisible button to be selected. To avoid this issue, simply set tabindex attributes accordingly and omit a tabindex attribute on the invisible submit button. While it may seem out of place to promote these styles to !important, they should prevent any framework or existing button styles from interfering with this fix. Also, those inline styles are definitely poor form, but we're proving concepts here... not writing production code.

Answer

HTML 4 does not make it explicit. The current HTML5 working draft specifies that the first submit button must be the default:

A form element's default button is the first submit button in tree order whose form owner is that form element.

If the user agent supports letting the user submit a form implicitly (for example, on some platforms hitting the "enter" key while a text field is focused implicitly submits the form), then doing so for a form whose default button has a defined activation behavior must cause the user agent to run synthetic click activation steps on that default button.

Answer

I think this post would help if someone wants to do it with jQuery:

http://greatwebguy.com/programming/dom/default-html-button-submit-on-enter-with-jquery/

The basic solution is:

$(function() {
    $("form input").keypress(function (e) {
    if ((e.which && e.which == 13) || (e.keyCode && e.keyCode == 13)) {
        $('input[type=submit].default').click();
        return false;
    } else {
        return true;
    }
    });
});

and another I liked was:

jQuery(document).ready(function() {
$("form input, form select").live('keypress', function (e) {
if ($(this).parents('form').find('button[type=submit].default, input[type=submit].default').length <= 0)
return true;

if ((e.which && e.which == 13) || (e.keyCode && e.keyCode == 13)) {
$(this).parents('form').find('button[type=submit].default, input[type=submit].default').click();
return false;
} else {
return true;
}
});
}); 
Answer

I had a form with 11 submit buttons on it, and it would always use the first submit button when the user pressed enter. I read elsewhere that it is not a good idea (bad practice) to have more than one submit button on a form, and the best way to do this is have the button you want as default, as the only submit button on the form. The other buttons should be made into "TYPE=BUTTON" and an onClick event added that calls your own submit routine in Javascript. Something like this :-

<SCRIPT Language="JavaScript">
function validform()
{
  // do whatever you need to validate the form, and return true or false accordingly
}

function mjsubmit()
{
  if (validform()) { document.form1.submit(); return true;}
  return false;
}
</SCRIPT>
<INPUT TYPE=BUTTON NAME="button1" VALUE="button1" onClick="document.form1.submitvalue='button1'; return mjsubmit();">
<INPUT TYPE=BUTTON NAME="button2" VALUE="button2" onClick="document.form1.submitvalue='button2'; return mjsubmit();">
<INPUT TYPE=SUBMIT NAME="button3" VALUE="button3" onClick="document.form1.submitvalue='button3'; return validform();">
<INPUT TYPE=BUTTON NAME="button4" VALUE="button4" onClick="document.form1.submitvalue='button4'; return mjsubmit();">

Here, button3 is the default, and although you are programmatically submitting the form with the other buttons, the mjsubmit routine validates them. HTH.

Answer

This can now be solved using flexbox:

HTML

<form>
    <h1>My Form</h1>
    <label for="text">Input:</label>
    <input type="text" name="text" id="text"/>

    <!-- Put the elements in reverse order -->
    <div class="form-actions">
        <button>Ok</button> <!-- our default action is first -->
        <button>Cancel</button>
    </div>
</form>

CSS

.form-actions {
    display: flex;
    flex-direction: row-reverse; /* reverse the elements inside */
}

Explaination
Using flex box, we can reverse the order of the elements in a container that uses display: flex by also using the CSS rule: flex-direction: row-reverse. This requires no CSS or hidden elements. For older browsers that do not support flexbox, they still get a workable solution but the elements will not be reversed.

Demo
http://codepen.io/Godwin/pen/rLVKjm

Answer

I struggled with the same question since i had submit button in the middle of the from which redirected submit to another page, like so:

<button type="submit" onclick="this.form.action = '#another_page'">More</button>

When user pressed enter key, this button was clicked instead of another submit button.

So i did some primitive tests by creating a from with multiple submit buttons and different visibility options and onclick event alerting which button was clicked: https://jsfiddle.net/aqfy51om/1/

Browsers and OS'es i used for testing:

WINDOWS

  • Google Chrome 43 (c'mon google :D)
  • Mozilla Firefox 38
  • Internet Explorer 11
  • Opera 30.0

OSX

  • Google Chrome 43
  • Safari 7.1.6

Most of these browsers clicked very first button despite the visibility options applied exept IE and Safari which clicked the third button, which is "visible" inside "hidden" container:

<div style="width: 0; height: 0; overflow: hidden;">
    <button type="submit" class="btn btn-default" onclick="alert('Hidden submit button #3 was clicked');">Hidden submit button #3</button>
</div>

So my suggestion, which i'm going to use myself, is:

If you form has multiple submit buttons with different meaning, then include submit button with default action at the beginning of the form which is either:

  1. Fully visible
  2. Wrapped in a container with style="width: 0; height: 0; overflow: hidden;"

EDIT Another option might be to offset the button(still at the beginning of the from) style="position: absolute; left: -9999px; top: -9999px;", just tried it in IE - worked , but i have no idea what else it can screw up, for example printing..

Answer

From your comments:

A consequence is that, if you have multiple forms submitting to the same script, you can't rely on submit buttons to distinguish them.

I drop an <input type="hidden" value="form_name" /> into each form.

If submitting with javascript: add submit events to forms, not click events to their buttons. Saavy users don't touch their mouse very often.

Answer

When you have multiple submit buttons in a single form and a user presses the ENTER key to submit the form from a text field, this code overrides default functionality, by calling the submit event on the form from the key press event. Here is that code:

$('form input').keypress(function(e){

    if ((e.which && e.which == 13) || (e.keyCode && e.keyCode == 13)){ $(e.target).closest('form').submit(); return false; }
    else return true;

});
Answer

Strange that the first button Enter goes always to the first button regardless is visible or not, e.g. using jquery show/hide(). Adding attribute .attr('disabled', 'disabled') prevent receiving Enter submit button completely. It's problem for example when adjusting Insert/Edit+Delete button visibility in record dialogs. I found less hackish and simple placing Edit in front of Insert

<button type="submit" name="action" value="update">Update</button>
<button type="submit" name="action" value="insert">Insert</button>
<button type="submit" name="action" value="delete">Delete</button>

and use javascript code:

$("#formId button[type='submit'][name='action'][value!='insert']").hide().attr('disabled', 'disabled');
$("#formId button[type='submit'][name='action'][value='insert']").show().removeAttr('disabled');
Answer

my recipe:

<form>
<input type=hidden name=action value=login><!-- the magic! -->

<input type=text name=email>
<input type=text name=password>

<input type=submit name=action value=login>
<input type=submit name=action value="forgot password">
</form>

It will send the default hidden field if none of the buttons are 'clicked'.

if they are clicked, they have preference and it's value is passed.

Answer

Another solution I've used is to just have one button in the form, and fake the other buttons.

Here's an example:

<form>
  <label for="amount">Amount of items</label>
  <input id="amount" type="text" name="amount" />
  <span id="checkStock" class="buttonish">Check stock</span>
  <button type="submit" name="action" value="order">Place order</button>
</form>

I then style the span elements to look like a button. A JS listener observes the span and performs the desired operation once clicked.

Not necessarily right for all situations, but at least it's pretty easy to do.

Answer

EDIT: Sorry, when writing this answer I was thinking about submit buttons in the general sense. The answer below is not about multiple type="submit" buttons, as it leaves only one type="submit" and change the other to type="button". I leave the answer here as reference in case helps someone that can change the type in their form:

To determine what button is pressed when hitting enter, you can mark it up with type="submit", and the other buttons mark them with type="button". For example:

<input type="button" value="Cancel" />
<input type="submit" value="Submit" />
Answer

From the HTML 4 spec:

If a form contains more than one submit button, only the activated submit button is successful.

This means that given more than 1 submit button and none activated (clicked), none should be successful.

And I'd argue this makes sense: Imagine a huge form with multiple submit-buttons. At the top, there is a "delete this record"-button, then lots of inputs follow and at the bottom there is an "update this record"-button. A user hitting enter while in a field at the bottom of the form would never suspect that he implicitly hits the "delete this record" from the top.

Therefore I think it is not a good idea to use the first or any other button it the user does not define (click) one. Nevertheless, browsers are doing it of course.

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