Bad value for attribute “src” on element “img”: Fragment is not allowed for data: URIs according to RFC 2397.

A data: URI embeds resource content directly in a URL rather than pointing to an external file. It follows the format data:[<mediatype>][;base64],<data>. RFC 2397, which governs this scheme, explicitly states that fragment identifiers (the # character followed by a fragment name) are not valid in data: URIs.

This issue most commonly arises when developers try to reference a specific element inside an embedded SVG — for example, a particular <symbol> or element with an id — by appending a fragment like #icon-name to a data: URI. While fragments work in standard URLs (e.g., icons.svg#home), the data: URI scheme simply doesn’t support them.

Why It Matters

• Standards compliance: Browsers may handle invalid data: URIs inconsistently. Some may silently ignore the fragment, while others may fail to render the image entirely.
• Portability: Code that relies on non-standard behavior in one browser may break in another or in a future update.
• Accessibility and tooling: Validators, linters, and assistive technologies expect well-formed URIs. An invalid URI can cause unexpected issues down the chain.

How to Fix It

You have several options depending on your use case:

1. Remove the fragment from the data: URI. If the embedded content is a complete, self-contained image, it doesn’t need a fragment reference.
2. Inline the SVG directly into the HTML document. This lets you reference internal id values with standard fragment syntax using <use> elements.
3. Use an external file instead of a data: URI. Standard URLs like icons.svg#home fully support fragment identifiers.
4. Encode the full, standalone SVG into the data: URI so that it contains only the content you need, eliminating the need for a fragment reference.

Examples

❌ Incorrect: Fragment in a data: URI

<img
  src="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg'%3E%3Csymbol id='icon'%3E%3Ccircle cx='10' cy='10' r='10'/%3E%3C/symbol%3E%3C/svg%3E#icon"
  alt="Icon">

The #icon fragment at the end of the data: URI violates RFC 2397 and triggers the validation error.

✅ Correct: Self-contained SVG in a data: URI (no fragment)

Embed only the content you need directly, without wrapping it in a <symbol> or referencing a fragment:

<img
  src="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 20 20'%3E%3Ccircle cx='10' cy='10' r='10'/%3E%3C/svg%3E"
  alt="Icon">

✅ Correct: External SVG file with a fragment

Move the SVG to a separate file and reference the specific symbol using a standard URL fragment:

<img src="icons.svg#icon" alt="Icon">

✅ Correct: Inline SVG with <use> referencing an internal id

If you need to reference individual symbols from a sprite, inline the SVG and use fragment references within the same document:

<svg xmlns="http://www.w3.org/2000/svg" hidden>
  <symbol id="icon-home" viewBox="0 0 20 20">
    <path d="M10 2 L2 10 L4 10 L4 18 L16 18 L16 10 L18 10 Z"/>
  </symbol>
</svg>

<svg width="20" height="20" aria-hidden="true">
  <use href="#icon-home"></use>
</svg>

This approach gives you full control over individual icons without needing data: URIs at all, and it’s the most flexible option for icon systems.

Learn more:

MDN Reference

MDN Web Docs: data URLs

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MDN Reference

The img element - MDN Web Docs

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WHATWG Spec

Embedded content - WHATWG HTML Standard

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