web-performance-seo

Web Performance SEO: Accessibility Contrast Error Fix

When to use

• PSI/Lighthouse accessibility shows "!" or error instead of a numeric score
• color-contrast audit errors or getImageData failures
• Need to improve accessibility signals that impact SEO

Workflow

1. Reproduce
   • Run Lighthouse or PSI; capture failing audit names.
2. Scan code for common triggers
   • CSS filters/backdrop blur, mix-blend-mode
   • OKLCH/OKLAB colors
   • Low opacity backgrounds (< 0.4)
   • Gradient text with color: transparent
   • Text over images without opaque overlays
3. Fix in priority order
   • Remove filters/blend modes
   • Convert OKLCH/OKLAB to HSL/RGB
   • Raise opacity thresholds
   • Add solid-color fallback for gradient text
   • Add overlay behind text on images
4. Verify locally with Lighthouse/axe
5. Verify in PSI after deployment

Fast scan commands

rg -n "backdrop-blur|filter:|mix-blend-mode" .
rg -n "oklch|oklab" .
rg -n "/10|/20|/30|opacity-25|opacity-0" .
rg -n "background-clip.*text|color.*transparent" .

Fix patterns

Remove filters (critical)

// Before
<div className="bg-card/50 backdrop-blur-sm">...</div>
// After
<div className="bg-card/80">...</div>

Convert OKLCH/OKLAB to HSL/RGB

/* Before */
:root { --primary: oklch(0.55 0.22 264); }
/* After */
:root { --primary: hsl(250, 60%, 50%); }

Raise opacity thresholds

• Backgrounds >= 0.4 (prefer >= 0.6)
• Replace /10 -> /40, /20 -> /40, /30 -> /60

Gradient text fallback

.title { color: #111111; }
@media (prefers-contrast: no-preference) {
  .title.with-gradient {
    background: linear-gradient(90deg, #0ea5e9, #6366f1);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
  }
}
@media (forced-colors: active) {
  .title.with-gradient { background: none; color: CanvasText; }
}

Overlay for text on images

<div className="relative">
  <img src="/hero.jpg" alt="Hero" />
  <div className="absolute inset-0 bg-black/60"></div>
  <h1 className="relative text-white">Title</h1>
</div>

Acceptance criteria

• Accessibility score is numeric (not "!")
• color-contrast audit passes or lists actionable items
• Contrast ratios >= 4.5:1 for normal text, >= 3:1 for large text

Notes

• "!" indicates audit failure, not a low score.
• Always test locally before waiting for PSI updates.