How Do Browsers Determine the Default Submit Button on HTML Forms?

Determining the Default Submit Button on HTML Forms

When a form is submitted without explicitly specifying a submit button, such as by pressing Enter or calling HTMLFormElement.submit() in JavaScript, the browser must determine which submit button to use.

The Standard's Silence

The HTML specifications do not specify how to handle this situation when submitting a form via pressing Enter in a non-textarea field.

Browser Behavior

Different browsers handle this ambiguity in various ways:

• Firefox, Opera, and Safari typically use the first submit button in the form.
• Internet Explorer may use the first submit button or none at all, depending on conditions that are not clearly defined.
• When JavaScript submits the form, no submit button is considered "successful," and their values are not included in the submitted data.

Implications

This behavior has implications for both event handling and data submission. Attaching an onclick event handler to a submit button may not fire when the form is submitted via Enter, and the data sent to the web server may differ depending on the browser.

Avoidance Recommendations

To avoid these ambiguities, best practices recommend avoiding relying on default submit button behavior. Instead, explicitly specify which button should be submitted when the form is submitted via Enter or JavaScript.

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