HTML check: Bad value “” for attribute “id” on element X: An ID must not be the empty string.

About This HTML Issue

The validator reports “Bad value “” for attribute id on element X: An ID must not be the empty string” when any element includes an empty id attribute. Per the HTML standard, id is a global attribute used as a unique document-wide identifier. An empty identifier is not a valid value and is ignored by some features, leading to hard-to-debug issues.

This matters for accessibility and interoperability. Features that depend on IDs—fragment navigation (#target), <label for>, ARIA attributes like aria-labelledby/aria-controls, and DOM APIs such as document.getElementById()—require a non-empty, unique value. Empty IDs break these links, can degrade assistive technology output, and violate conformance, which may hide bugs across browsers.

How to fix:

If the element doesn’t need an identifier, remove the id attribute entirely.
If it needs one, provide a non-empty, unique value, e.g., id="main-content".
Ensure uniqueness across the page; each id must occur only once.
Use simple, predictable tokens: avoid spaces, prefer lowercase letters, digits, hyphens, and underscores (e.g., feature-1). While the spec allows a broad range of characters, sticking to URL- and selector-friendly characters avoids pitfalls.

Examples

Example that triggers the validator error (empty id)

<div id=""></div>

Correct: remove an unnecessary empty id

<div></div>

Correct: provide a meaningful, unique id

<section id="features"></section>

Problematic label association with empty id (invalid)

<label for="">Email</label>
<input type="email" id="">

Correct label–control association

<label for="email">Email</label>
<input type="email" id="email">

Correct ARIA relationship

<h2 id="pricing-heading">Pricing</h2>
<section aria-labelledby="pricing-heading">
  <p>Choose a plan.</p>
</section>

Correct fragment navigation target

<nav>
  <a href="#contact">Contact</a>
</nav>
<section id="contact">
  <h2>Contact us</h2>
</section>

Minimal full document (validated) demonstrating proper ids

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Valid IDs Example</title>
  </head>
  <body>
    <main id="main-content">
      <h1 id="page-title">Welcome</h1>
      <p>Jump to the <a href="#details">details</a>.</p>
      <section id="details">
        <h2>Details</h2>
      </section>
      <form>
        <label for="email">Email</label>
        <input id="email" type="email">
      </form>
    </main>
  </body>
</html>

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Learn more:

MDN Reference

Global attributes: id

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