methodology / Performance / #35
Lazy loading on below-fold images
#35 · Recommended · Web Quality · weighted · Performance · weight 0.7% · impl implemented · method v1.2.0
Web Quality factor
This factor is part of Web Quality — the weighted 0..100 score that sits above Web Standards. Its weight depends on what kind of site is being measured. Web Standards items take priority; this factor only enters the score once Web Standards passes.
- Base weight
- 0.7 applied to every site type unless overridden below
- Why this weight
- Lazy loading — high impact on long, image-heavy pages.
Per-site-type overrides
| Site type | Weight | Δ vs base |
|---|---|---|
| E-commerce | 1.0 | +0.3 |
| News / Publisher | 0.9 | +0.2 |
| Personal site | 0.4 | -0.3 |
| Media / Streaming | 1.0 | +0.3 |
Site types not listed inherit the base weight.
What this means for your business
When every image loads at once, the top of your page stalls because the phone is busy fetching pictures nobody can see yet. Loading them as a visitor scrolls is a one-line fix that makes the first screen pop in faster.
Plain title: Photos lower on the page wait their turn
What we measure
Lazy-loaded images don't download until visitors scroll near them, cutting initial page weight and speeding up first paint.
How to improve your score
Add `loading="lazy"` to `<img>` tags below the fold. WordPress 5.5+ adds it automatically. Don't lazy-load above-fold or hero images — that delays LCP.
Facts
Implementation notes
Count `<img>` tags with vs without the `loading="lazy"` attribute and report the ratio.
Scoring
Scoring formulas are versioned with the methodology. The current method (v1.2.0) maps raw measurements to pass, warn, fail. Factor weights determine how much each contributes to the composite — see the methodology index for the full table.
Version history
| Version | Change | Date |
|---|---|---|
| v1.2.0 | Factor introduced. Status: live. Scoring impl: implemented. | 2026-04-25 |