ContentWidthConstrained [rule] v1.0.0

Long-form content containers (article, blog post, documentation, prose) MUST cap their width at approximately 65ch (≈ 720px at 16px/1ch). Full-bleed layouts force readers to track lines wider than the eye can follow, increasing fatigue and abandonment.

Checks

• @community/check-content-width-constrained

Applies To

@community/type-html-artifact

Meta

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

Severity

medium

Severity Combination

long-form container has no max-width                     → BLOCK
long-form container max-width > 90ch                     → BLOCK
long-form container max-width 75–90ch                    → WARN
long-form container max-width 60–75ch                    → PASS

Failure Mode

Articles read like website copy at 1440px-wide; readers' eyes lose track of the next line; bounce rate on read-time-3min+ pages spikes. Search engines (Core Web Vitals beyond) increasingly weight readability metrics.

Remediation

• Set the article wrapper: article { max-width: 65ch; margin-inline: auto; }.
• Allow media (figures, code blocks, callouts) to extend wider via figure { max-width: 90ch; margin-inline: -clamp(0px, 12vw, 200px); }.
• Combine with @community/rule-line-length-optimal at the paragraph level for defense-in-depth.
• Use ch units, not px — ch adapts to font choice.

Exceptions

• • Case: Reference / API documentation with code-heavy content
  • Allowed When: Code samples need ≥ 80ch; the doc may run 80–90ch and rely on code being the primary content.
• • Case: Two-column layout
  • Allowed When: A column-width: 30ch two-column layout achieves comfortable measure at wider container widths.

ContentWidthConstrained [rule] v1.0.0

Long-form content containers (article, blog post, documentation, prose) MUST cap their width at approximately 65ch (≈ 720px at 16px/1ch). Full-bleed layouts force readers to track lines wider than the eye can follow, increasing fatigue and abandonment.

Checks

• @community/check-content-width-constrained

Applies To

@community/type-html-artifact

Meta

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

Severity

medium

Severity Combination

long-form container has no max-width                     → BLOCK
long-form container max-width > 90ch                     → BLOCK
long-form container max-width 75–90ch                    → WARN
long-form container max-width 60–75ch                    → PASS

Failure Mode

Articles read like website copy at 1440px-wide; readers' eyes lose track of the next line; bounce rate on read-time-3min+ pages spikes. Search engines (Core Web Vitals beyond) increasingly weight readability metrics.

Remediation

• Set the article wrapper: article { max-width: 65ch; margin-inline: auto; }.
• Allow media (figures, code blocks, callouts) to extend wider via figure { max-width: 90ch; margin-inline: -clamp(0px, 12vw, 200px); }.
• Combine with @community/rule-line-length-optimal at the paragraph level for defense-in-depth.
• Use ch units, not px — ch adapts to font choice.

Exceptions

• • Case: Reference / API documentation with code-heavy content
  • Allowed When: Code samples need ≥ 80ch; the doc may run 80–90ch and rely on code being the primary content.
• • Case: Two-column layout
  • Allowed When: A column-width: 30ch two-column layout achieves comfortable measure at wider container widths.

Relations

related: [@community/rule-line-length-optimal, @community/rule-body-readability, @community/fact-optimal-line-length] see-also: [@community/check-content-width-constrained] validates-with: [@community/fact-optimal-line-length]

Applies To

@community/type-html-artifact

Meta

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

Severity

medium

Validates With

• @community/fact-optimal-line-length

Severity Combination

long-form container has no max-width                     → BLOCK
long-form container max-width > 90ch                     → BLOCK
long-form container max-width 75–90ch                    → WARN
long-form container max-width 60–75ch                    → PASS

Failure Mode

Articles read like website copy at 1440px-wide; readers' eyes lose track of the next line; bounce rate on read-time-3min+ pages spikes. Search engines (Core Web Vitals beyond) increasingly weight readability metrics.

Remediation

• Set the article wrapper: article { max-width: 65ch; margin-inline: auto; }.
• Allow media (figures, code blocks, callouts) to extend wider via figure { max-width: 90ch; margin-inline: -clamp(0px, 12vw, 200px); }.
• Combine with @community/rule-line-length-optimal at the paragraph level for defense-in-depth.
• Use ch units, not px — ch adapts to font choice.

Exceptions

• • Case: Reference / API documentation with code-heavy content
  • Allowed When: Code samples need ≥ 80ch; the doc may run 80–90ch and rely on code being the primary content.
• • Case: Two-column layout
  • Allowed When: A column-width: 30ch two-column layout achieves comfortable measure at wider container widths.

See Also

• @community/check-content-width-constrained