Rule of Useful Space
Larger screens expose useful detail and preserve legibility.
Requirement
For the same task and data state, moving to a larger supported viewport must preserve the critical comparison set. Where additional evidence helps the task, define which extra rows, columns, time history, or comparison panels become visible at larger sizes. Preserve readable type and interaction targets as density changes.
Why
Additional screen area is an opportunity to improve comparison and inspection. Stretching containers alone does not demonstrate that improvement.
Application
Judge density by useful, distinct observations and relationships. Repeated values, larger cards, and decorative marks do not count as additional evidence. A larger carrier table might expose volume and service breakdowns while keeping cost and reliability visible. Do not increase density by shrinking text below the project's readable type scale. Preserve usable controls as density changes. For prose, use bounded reading widths and natural word spacing; avoid fully justified paragraphs. The default control-size and prose checks are scoped review warnings. Finite comparisons: Align peer headings and sample surfaces through shared layout relationships rather than fixed-height explanation slots or empty panel allowances. Let wrapped content determine the required height. A scoped ceiling may catch a known regression at one declared viewport and state; pair it with legibility and required-context checks, and do not apply it unchanged to enlarged text, different content, or narrower layouts.
Exception
A finite comparison or focused task may already show all useful evidence. Retain useful whitespace and bounded reading widths in that case; do not manufacture content to meet an occupancy target. Comparative allocation: DR-019 adds opt-in viewport-growth yield: fractional growth of qualifying evidence divided by fractional growth of usable region area, with reference identities preserved. Its explicit finite-set exception distinguishes an already complete task from empty container growth. The metric cannot decide which evidence is useful.
Review
Assess both the whole layout and detail at its intended reading size for every target viewport. A reduced overview alone cannot establish legibility on a large screen. Viewport dimensions refer to CSS pixels; account for browser zoom and display scaling when choosing representative screen sizes. Decision surfaces: Retain enough map or chart area for the required labels and marks. Compact the supporting context, not the type. Reuse region-density on scoped text regions as a geometry proxy; a large map box is not evidence of semantic density. Declared repeated metrics and scalar container heights can supply additional partial checks. Expanded decision-surface reference. Discovery application: Reduce redundant spacing before reducing readable type. Bound the gap between a heading and its description without fixing the item height; let wrapped titles and enlarged text use the space they need. Exact type scales, icon sizes, gaps, and column choices remain project decisions.
Examples
The pair isolates this rule. A good example is not approval of the entire interface.
Good for this task
A larger viewport reveals useful service and volume detail while keeping text readable.
Carrier comparison
Bad for this task
The same sparse cards merely stretch wider, or additional density is achieved by shrinking type.
Carrier comparison
These synthetic fixtures illustrate the stated comparison. Native checks can support review of declared scales, context, encodings, geometry, and legibility; they do not establish data truth or task relevance. Review the requirement and exceptions above.
Enforcement
automated is the strongest mechanism Viewrule expects for the complete rule. Partial checks can still provide supporting evidence without proving the whole requirement.