Performance & Core Web Vitals
Layout shift (CLS)
Content jumps while loading — missing image dimensions, fonts, or ads. Fix in Images and Pulse.
Typical symptom
PageSpeed shows high CLS, user taps the wrong button, layout moves after paint.
Puluno modules
ImagesPulse
Undo change
Partial — see article
Issue codes
cls_high, images_missing_dimensions
What you see
- Finding
cls_highorimages_missing_dimensions. - Lighthouse: Cumulative Layout Shift above 0.1 (mobile).
- Banner / cookie bar pushes content after load.
- Images without
width/height— empty gap, then a jump.
Why it happens
CLS measures unexpected layout movement. Google cares about UX, not meta keywords.
Common causes:
<img>without width/height (theme, page builder).- Webfont loaded late — FOUT/FOIT.
- Lazy iframe / map / ad injected above the fold.
- Cookie / GDPR bar injected into
<body>without reserved space. - Dynamic WooCommerce cart in header.
What Puluno does
| Phase | Module | Action |
|---|---|---|
| Diagnose | Explorer + Pulse | CLS score, elements missing dimensions |
| Apply | Images | add width/height on content images |
| Apply | Pulse | reserve space for fonts / defer non-critical CSS (safe) |
| Verify | Explorer / Lab | same URL — cls finding drops |
CLS from third-party ads is not removed by Pulse — only identified.
Step by step
- Explorer + optional Lab Performance on homepage (mobile).
- Find which element shifts (Lighthouse shift trace).
- Images Apply — dimensions on content images and logo.
- Theme: fixed cookie bar height or
font-display: swap+ reservation. - Pulse safe fixes — when the finding recommends CSS/JS defer.
- Verify: same URL —
cls_highgone or lower severity. - Test on a real Android device — lab ≠ always field.
Rollback — undo the change
- Images — revert dimensions on specific files.
- Pulse — rollback batch for CSS/JS changes.
When it is not Puluno
- AdSense / GTM banner — trim in tag manager.
- Page builder animations — disable auto height animations above the fold.
- Issue only in CrUX field data — rollout takes 28 days; lab Verify is enough to prove Apply.
Related: Slow site — LCP — often the same hero image.
Related situations
Module manual