type/weight-conformance

Status: active

Default severity: warning

What it checks

For every node in the snapshot, the rule reads the computed font-weight value and parses it as a u16. A violation fires when the parsed weight is not present in type.weights.

The rule MUST skip a node when:

• the node has no computed font-weight value;
• the value does not parse as a u16 (e.g. bold, normal);
• or type.weights is empty (the rule is a no-op).

Chromium resolves keyword weights (bold → 700, normal → 400) in getComputedStyle, so in practice the rule sees numeric values.

Why it matters

Design systems restrict font weights to a small set (often 400 and 700, or a wider range for variable fonts). An off-scale weight like 450 or 550 may render differently across browsers and fonts, creating inconsistency that is hard to spot by eye.

Example violation

{
  "rule_id": "type/weight-conformance",
  "severity": "warning",
  "message": "`html > body > span` has off-scale font-weight 450; expected a value from type.weights.",
  "selector": "html > body > span",
  "viewport": "desktop",
  "dom_order": 3,
  "fix": {
    "kind": {
      "kind": "css_property_replace",
      "property": "font-weight",
      "from": "450",
      "to": "400"
    },
    "description": "Snap `font-weight` to the nearest type-scale weight (400).",
    "confidence": "medium"
  },
  "doc_url": "https://plumb.aramhammoudeh.com/rules/type-weight-conformance"
}

Configuration

type.weights is the list of allowed font-weight values. Default is empty (the rule is a no-op).

[type]
weights = [100, 300, 400, 500, 700, 900]

The fix suggests the nearest allowed weight by absolute delta. Ties resolve to the lower weight.

Suppression

Disable the rule for an entire run:

[rules."type/weight-conformance"]
enabled = false

Bump or lower the severity:

[rules."type/weight-conformance"]
severity = "info"

See also

• type/family-conformance — the sibling rule for font-family tokens.
• type/scale-conformance — the sibling rule for font-size tokens.