A “script” element with a “src” attribute must not have a “type” attribute whose value is anything other than the empty string, a JavaScript MIME type, or “module”.

The <script> element serves two distinct purposes in HTML: loading executable scripts and embedding non-executable data blocks. When the src attribute is present, the element is always being used to load an external script, so the type attribute must reflect a valid script type. Setting type to something like "text/html", "text/plain", or an invented value like "wrong" tells the browser this is not JavaScript, which means the external file referenced by src will be fetched but never executed — almost certainly not what the author intended.

The HTML specification restricts the allowed type values for <script src="..."> to three categories:

• An empty string (type=""): Treated the same as the default, which is JavaScript.
• A JavaScript MIME type: This includes text/javascript, application/javascript, and other legacy JavaScript MIME types. Since text/javascript is the default, specifying it is redundant.
• module: Indicates the script should be treated as a JavaScript module, enabling import/export syntax and deferred execution by default.

Any value outside these categories — such as text/html, application/json, or a made-up string — is invalid when src is present.

Why this matters

Broken functionality: A non-JavaScript type on a <script> with src prevents the browser from executing the loaded file. The script is effectively dead code that still costs a network request.

Standards compliance: The HTML living standard explicitly forbids this combination. Validators flag it because it almost always indicates a mistake — either the wrong type was applied, or the src attribute was added by accident.

Maintainability: Future developers reading the code may be confused about whether the script is supposed to execute or serve as an inert data block. Keeping markup valid makes intent clear.

How to fix it

1. Remove the type attribute entirely. This is the best approach for classic JavaScript. The default behavior is text/javascript, so no type is needed.
2. Use type="module" if the script uses ES module syntax (import/export).
3. If you intended a data block (e.g., embedding JSON or a template), remove the src attribute and place the content inline inside the <script> element instead. Data blocks with non-JavaScript types cannot use src.

Examples

Invalid: non-JavaScript types with src

These all trigger the validation error because the type value is not a JavaScript MIME type, an empty string, or "module":

<script type="text/html" src="template.html"></script>

<script type="application/json" src="data.json"></script>

<script type="text/plain" src="app.js"></script>

<script type="wrong" src="app.js"></script>

Valid: omitting the type attribute

The simplest and recommended fix for classic scripts — just drop type:

<script src="app.js"></script>

Valid: using a JavaScript MIME type

This is valid but redundant, since text/javascript is already the default. The validator may suggest omitting it:

<script type="text/javascript" src="app.js"></script>

Valid: using type="module"

Use this when the external script uses ES module syntax:

<script type="module" src="app.js"></script>

Valid: using an empty type attribute

An empty string is treated as the default. It’s valid but unnecessary, and the validator may suggest removing it:

<script type="" src="app.js"></script>

Valid: data blocks without src

If you need a non-JavaScript type for an inline data block, remove the src attribute and place the content directly inside the element:

<script type="application/json" id="config">
  {
    "apiUrl": "https://example.com/api",
    "debug": false
  }
</script>

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