no-nonstandard-features

Warns about elements and attributes marked as non-standard in the HTML specification data bundled with markuplint.

info

Split from the former no-unsupported-features rule's checkNonStandard option (#3989). Enabling this rule is equivalent to the old checkNonStandard: true. See the no-unsupported-browser-features rule for the browserslist-based support check, or the no-experimental-features rule for experimental features.

Default Severity

warning

Options

Option	Type	Default	Description
ignoreFeatures	string[]	[]	Features to ignore.

ignoreFeatures Format

Uses exact string matching (no glob or wildcard patterns).

• "dialog" — Ignores the <dialog> element (exact match on element name).
• "input[list]" — Ignores the list attribute on <input> elements.

Examples

❌ Examples of incorrect code for this rule

<canvas moz-opaque></canvas>

✅ Examples of correct code for this rule

<canvas></canvas>

Migration from deprecated-element

In v4.x, the deprecated-element rule detected deprecated, obsolete, and non-standard elements. In v5.x, the non-standard detection has moved to this rule.

{
  "rules": {
    "no-nonstandard-features": true
  }
}

If you use the recommended preset, this is already enabled automatically via the compat preset.

Interface

{
  "no-nonstandard-features": boolean
}

Options

{
  "no-nonstandard-features": {
    "options": {
      "ignoreFeatures"?: string[]
    }
  }
}

Property	Type	Default Value	Description
ignoreFeatures	string[]	undefined	Features to ignore. Element name ("dialog") or attribute pattern ("input[list]").

Default Severity

warning