Bad value “” for attribute “action” on element “form”: Must be non-empty.

The action attribute tells the browser where to send form data when the form is submitted. According to the WHATWG HTML living standard, if the action attribute is specified, its value must be a valid non-empty URL potentially surrounded by spaces. An empty string ("") does not satisfy this requirement, which is why the W3C validator flags it.

While some developers use action="" intending the form to submit to the current page’s URL, this approach is non-conforming HTML. Browsers do typically interpret an empty action as “submit to the current URL,” but relying on this behavior is unnecessary since simply omitting the action attribute achieves the same result in a standards-compliant way. When no action attribute is present, the form submits to the URL of the page containing the form — this is the defined default behavior per the HTML specification.

This issue matters for several reasons:

• Standards compliance: Non-conforming HTML can lead to unexpected behavior across different browsers or future browser versions.
• Maintainability: Using the correct approach makes your intent clearer to other developers. Omitting action explicitly signals “submit to the current page,” while action="" looks like a mistake or a placeholder that was never filled in.
• Tooling: Build tools, linters, and automated testing pipelines that rely on valid HTML may flag or break on this error.

How to Fix

You have two options:

1. Remove the action attribute if you want the form to submit to the current page URL.
2. Provide a valid URL if the form should submit to a specific endpoint.

Examples

❌ Invalid: Empty action attribute

<form action="" method="post">
  <label for="email">Email:</label>
  <input type="email" id="email" name="email">
  <button type="submit">Subscribe</button>
</form>

This triggers the error: Bad value “” for attribute “action” on element “form”: Must be non-empty.

✅ Fixed: Remove the action attribute

If you want the form to submit to the current page, simply omit action:

<form method="post">
  <label for="email">Email:</label>
  <input type="email" id="email" name="email">
  <button type="submit">Subscribe</button>
</form>

✅ Fixed: Provide a valid URL

If the form should submit to a specific endpoint, supply the URL:

<form action="/subscribe" method="post">
  <label for="email">Email:</label>
  <input type="email" id="email" name="email">
  <button type="submit">Subscribe</button>
</form>

✅ Fixed: Use a hash as a placeholder for JavaScript-handled forms

If your form is entirely handled by JavaScript and should not navigate anywhere, you can use a # as the action or, preferably, omit action and prevent submission in your script:

<form method="post" id="js-form">
  <label for="query">Search:</label>
  <input type="text" id="query" name="query">
  <button type="submit">Search</button>
</form>

document.getElementById('js-form').addEventListener('submit', function(e) {
  e.preventDefault();
  // Handle form data with JavaScript
});

In this case, omitting action is the cleanest solution. The JavaScript preventDefault() call stops the browser from actually submitting the form, so the action value is never used.

Learn more:

MDN Reference

HTML form element - action attribute

→

WHATWG Spec

HTML Standard - Forms

→

web.dev Article

Learn HTML: Forms

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