Section 188.8.131.52 Implicit submission of the W3C HTML5 spec says:
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.
Note: Consequently, if the default button is disabled, the form is not submitted when such an implicit submission mechanism is used. (A button has no activation behavior when disabled.)
Therefore, a standards-compliant way to disable any implicit submission of the form is to place a disabled submit button as the first submit button in the form:
<form action="..."> <!-- Prevent implicit submission of the form --> <button type="submit" disabled style="display: none" aria-hidden="true"></button> <!-- ... --> <button type="submit">Submit</button> </form>
<input type='text' onkeydown='return event.keyCode != 13;' />
If you don’t have a in your form, then just add the following to your <form>:
<form ... onkeydown="return event.key != 'Enter';">
<form ... onkeydown="return event.keyCode != 13;">