script type=text/javascript

type="text/javascript" dates from a time when the script language was genuinely in question: Netscape shipped JavaScript, Internet Explorer shipped JScript and VBScript, and HTML 4.01 made type a required attribute with no default. That stopped being true in HTML5, which defines the classic-script path as what happens when type is absent.

Why avoid

The attribute is not merely redundant, it is the only spelling the spec advises against. A <script> whose type is a JavaScript MIME type is processed exactly as one with no type at all, and the HTML Standard says authors should omit it. The value is also a legacy compatibility surface: text/javascript1.3, text/jscript and text/livescript are still accepted for content that has not been touched since the 1990s, which means a typo like text/javasript does not error — it silently makes the element a data block that never executes.

Carrying it forward teaches the wrong model of the attribute. type is now meaningful and load-bearing: module, importmap and speculationrules change what the element is. Treating it as boilerplate is how type="module" ends up deleted by a well-meaning cleanup.

Use instead

Omit it for classic scripts:

<script src="/app.js"></script>
<script>console.log("classic script");</script>

Keep it wherever it selects behaviour:

<script type="module" src="/app.js"></script>
<script type="importmap">{ "imports": { "lit": "/vendor/lit.js" } }</script>
<script type="application/json" id="state">{ "user": null }</script>

Detectability

Fully detectable, but not by the selector alone. script[type] is only a pre-filter: the verdict depends on whether the trimmed value is a JavaScript MIME type essence match, a sixteen-entry list the selector subset cannot enumerate. The decision therefore lives in packages/rules/logic/script/type-javascript-mime.ts.

Anything the logic does not recognise is left alone, and one exclusion is load-bearing: a type with parameters, such as text/javascript; charset=utf-8, is not an essence match, so the browser treats that element as a data block and never runs it. Removing the attribute would start executing code that has never executed. The same goes for a typo like text/javasript. Both are real bugs; neither is safe to autofix, so this rule does not claim them.

Resources

• HTML Standard — the type attribute — classic scripts are the no-type path; authors should omit it.
• MIME Sniffing Standard — JavaScript MIME type — the normative list of essences this rule matches.
• MDN — <script>: type — the legacy values and what each modern value selects.