MobileFirst [rule] v1.0.0

CSS responsive breakpoints MUST be authored mobile-first: base styles target the smallest viewport, and @media (min-width: ...) queries layer on enhancements for larger viewports. Desktop-first authoring (@media (max-width: ...)) requires the cascade to override styles repeatedly and tends to bloat mobile payloads.

Checks

• @community/check-mobile-first

Applies To

@community/type-html-artifact

Severity

medium

Severity Combination

>50% of breakpoints use max-width        → BLOCK
1–50% use max-width                      → WARN
all breakpoints use min-width            → PASS

Failure Mode

Mobile devices (the majority of traffic) parse and discard desktop styles; CSS specificity wars erupt as each breakpoint must un-set the previous; new components require copy-paste of all-but-mobile resets.

Remediation

• Refactor: write base styles for mobile, then @media (min-width: 640px) { ... } for tablet, @media (min-width: 1024px) { ... } for desktop.
• Adopt Tailwind's mobile-first variants (md: lg: xl:) — they enforce min-width by default.
• If a feature is desktop-only (e.g. a hover-dependent pattern), add it inside a min-width AND @media (hover: hover) and (pointer: fine) query.

Exceptions

• • Case: Print stylesheet
  • Allowed When: Print styles use @media print { ... } — orthogonal to width-based breakpoints.
• • Case: Print-like 'narrow desktop window' constraint
  • Allowed When: A specific desktop-only override is cleaner as a max-width override; flag with a comment but don't block.

MobileFirst [rule] v1.0.0

CSS responsive breakpoints MUST be authored mobile-first: base styles target the smallest viewport, and @media (min-width: ...) queries layer on enhancements for larger viewports. Desktop-first authoring (@media (max-width: ...)) requires the cascade to override styles repeatedly and tends to bloat mobile payloads.

Checks

• @community/check-mobile-first

Applies To

@community/type-html-artifact

Severity

medium

Severity Combination

>50% of breakpoints use max-width        → BLOCK
1–50% use max-width                      → WARN
all breakpoints use min-width            → PASS

Failure Mode

Mobile devices (the majority of traffic) parse and discard desktop styles; CSS specificity wars erupt as each breakpoint must un-set the previous; new components require copy-paste of all-but-mobile resets.

Remediation

• Refactor: write base styles for mobile, then @media (min-width: 640px) { ... } for tablet, @media (min-width: 1024px) { ... } for desktop.
• Adopt Tailwind's mobile-first variants (md: lg: xl:) — they enforce min-width by default.
• If a feature is desktop-only (e.g. a hover-dependent pattern), add it inside a min-width AND @media (hover: hover) and (pointer: fine) query.

Exceptions

• • Case: Print stylesheet
  • Allowed When: Print styles use @media print { ... } — orthogonal to width-based breakpoints.
• • Case: Print-like 'narrow desktop window' constraint
  • Allowed When: A specific desktop-only override is cleaner as a max-width override; flag with a comment but don't block.

Applies To

@community/type-html-artifact

Severity

medium

Validates With

• @community/fact-consistency-standards

Severity Combination

>50% of breakpoints use max-width        → BLOCK
1–50% use max-width                      → WARN
all breakpoints use min-width            → PASS

Failure Mode

Mobile devices (the majority of traffic) parse and discard desktop styles; CSS specificity wars erupt as each breakpoint must un-set the previous; new components require copy-paste of all-but-mobile resets.

Remediation

• Refactor: write base styles for mobile, then @media (min-width: 640px) { ... } for tablet, @media (min-width: 1024px) { ... } for desktop.
• Adopt Tailwind's mobile-first variants (md: lg: xl:) — they enforce min-width by default.
• If a feature is desktop-only (e.g. a hover-dependent pattern), add it inside a min-width AND @media (hover: hover) and (pointer: fine) query.

Exceptions

• • Case: Print stylesheet
  • Allowed When: Print styles use @media print { ... } — orthogonal to width-based breakpoints.
• • Case: Print-like 'narrow desktop window' constraint
  • Allowed When: A specific desktop-only override is cleaner as a max-width override; flag with a comment but don't block.

See Also

• @community/check-mobile-first