MonospaceTabularNumerics [constraint] v1.0.0

Numeric data in tables, dashboards, financial UIs, and metric cards MUST use tabular-numeral rendering (font-variant-numeric: tabular-nums) — NOT a monospace typeface — unless the typeface is itself monospace for other semantic reasons (code, terminals). Monospace fonts are not required; tnum OpenType feature on a proportional font achieves column alignment without sacrificing aesthetics.

Target

numeric display in tables, dashboards, fintech UIs

Severity

medium

Meta

• License: Apache-2.0
• License Provenance: package-authorship-claim

Values

• • Required: font-variant-numeric: tabular-nums on all numeric table cells, balance displays, metric cards
• • Required: font-variant-numeric: lining-nums (or lnum) for numbers alongside capitals in headers
• • Allowed: Monospace font for CODE, hashes, IDs, terminal output, SKUs — where character-by-character alignment is the entire point
• • Forbidden: Switching to full monospace font (JetBrains Mono, Courier) solely for column alignment in a proportional UI — use tnum instead
• • Forbidden: Mixing proportional and tabular numerals within the same column of a data table

Approved Alternatives

• font-variant-numeric: tabular-nums lining-nums on numeric contexts
• CSS: .metric, td.number, .amount { font-variant-numeric: tabular-nums lining-nums; }
• CSS shorthand: font-variant: tabular-nums (applies tnum, compatible with most browsers)
• font-feature-settings: 'tnum' 1, 'lnum' 1 (explicit feature activation fallback)

MonospaceTabularNumerics [constraint] v1.0.0

Numeric data in tables, dashboards, financial UIs, and metric cards MUST use tabular-numeral rendering (font-variant-numeric: tabular-nums) — NOT a monospace typeface — unless the typeface is itself monospace for other semantic reasons (code, terminals). Monospace fonts are not required; tnum OpenType feature on a proportional font achieves column alignment without sacrificing aesthetics.

Target

numeric display in tables, dashboards, fintech UIs

Severity

medium

Meta

• License: Apache-2.0
• License Provenance: package-authorship-claim

Values

• • Required: font-variant-numeric: tabular-nums on all numeric table cells, balance displays, metric cards
• • Required: font-variant-numeric: lining-nums (or lnum) for numbers alongside capitals in headers
• • Allowed: Monospace font for CODE, hashes, IDs, terminal output, SKUs — where character-by-character alignment is the entire point
• • Forbidden: Switching to full monospace font (JetBrains Mono, Courier) solely for column alignment in a proportional UI — use tnum instead
• • Forbidden: Mixing proportional and tabular numerals within the same column of a data table

Approved Alternatives

• font-variant-numeric: tabular-nums lining-nums on numeric contexts
• CSS: .metric, td.number, .amount { font-variant-numeric: tabular-nums lining-nums; }
• CSS shorthand: font-variant: tabular-nums (applies tnum, compatible with most browsers)
• font-feature-settings: 'tnum' 1, 'lnum' 1 (explicit feature activation fallback)

Relations

related: [@community/fact-monospace-purpose, @community/rule-opentype-features-on, @community/rule-font-feature-settings]

Rationale

Tabular figures (tnum) ensure each digit occupies the same horizontal advance, causing numbers in adjacent rows to align vertically in a column — exactly what monospace achieves, but without the aesthetic penalty of fixed-width letters on non-numeric characters. Most quality fonts (Inter, Geist, Söhne, Source Serif 4, IBM Plex) ship tnum as an OpenType feature. Switching the entire UI to a monospace face to solve numeric alignment is the typographic equivalent of using a sledgehammer for a thumbtack.