Which Browser Behavior is Undefined for Default Form Submission Button?

Determining the Default Submit Button in HTML Forms

When submitting an HTML form without using specific submit buttons, such as via pressing the Enter key or through HTMLFormElement.submit() in JavaScript, browsers must determine which submit button, if any, to use by default.

Current Behavior

Experimental observations indicate a variation in behavior across browsers:

• Firefox, Opera, and Safari: Use the first submit button in the form when pressing Enter.
• Internet Explorer: May use the first submit button or none at all under unspecified conditions when pressing Enter.
• All major browsers: Do not use any submit button when submitting via JavaScript.

Standard Specifications

The HTML standards do not explicitly define the default submit button behavior for key presses. They only specify that a form is submitted when a submit element is activated, leaving the actual selection of the submit button to the user agent's interpretation.

Browser Implementation Variations

Since the standard does not provide strict guidelines, browsers exhibit different behavior when determining the default submit button:

• Internet Explorer: May use the submit button that appears first in the source code, but this behavior is uncertain.
• Firefox and Opera: Likely use the submit button with the lowest tabindex value, defaulting to the first defined button if none is specified.
• Other browser variations and conditions may also affect this behavior.

Recommendation

Given the lack of a defined standard, it is advisable to avoid relying on specific default submit button behaviors in your web applications. Consider explicitly defining the submit button's activation and intended behavior to ensure consistency across browsers.

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