Performance & Core Web Vitals
Slow site — LCP and hero image
Homepage LCP is high or Explorer flags a slow hero image. Fix path in Pulse and Images without guessing cache.
Typical symptom
Score drops on LCP, PageSpeed shows a large above-the-fold photo, the site feels slow on mobile.
Puluno modules
PulseImages
Undo change
Partial — see article
Issue codes
lcp_slow, lcp_image_missing, lcp_image_not_preloaded, heavy_images
What you see
- Explorer or Lab Performance reports LCP above the recommended threshold (often > 2.5 s on mobile).
- Findings
lcp_slow,heavy_images, orlcp_image_not_preloaded. - PageSpeed / Lighthouse points at a hero image, slider, or header logo as the LCP element.
- The client says “mobile feels slow” while TTFB looks fine.
Why it happens
LCP (Largest Contentful Paint) measures when the largest visible element is painted. On agency sites that is almost always an above-the-fold image, not analytics JavaScript.
Common causes:
- Full-resolution PNG/JPEG displayed much smaller in CSS.
- Missing
width/height→ layout wait. - No preload for the LCP image in
<head>. - Lazy-load applied to the hero by mistake.
- Cache serving an old asset after optimization.
What Puluno does
| Phase | Module | Action |
|---|---|---|
| Diagnose | Explorer + Pulse | LCP element, file weight, preload, dimensions |
| Apply | Images | WebP/AVIF, resize, lazy below the fold |
| Apply | Pulse | LCP preload, defer non-critical CSS/JS (safe fixes) |
| Verify | Explorer | Same URL — LCP finding gone or downgraded |
Puluno does not fix slow hosting TTFB — that is a different playbook.
Step by step
- Run Explorer on the client homepage (mobile profile).
- Open LCP / heavy image findings — note the asset URL.
- On WordPress: Puluno Center → Today — fix the hero via Images (resize + modern format).
- Pulse Center — apply safe fixes (LCP preload, defer non-critical JS) when recommended.
- Verify: same URL in Explorer — compare score and LCP.
- Purge cache (Pulse / hosting) and check in a private window.
Rollback — undo the change
- Images: before/after preview per file — revert individual assets (partial rollback).
- Pulse safe fixes: rollback the last batch in Pulse Center where supported.
- Preload tags in
<head>— rollback removes the tag; run Verify again.
A cross-module ledger in Center is coming — today, rollback per module.
When it is not Puluno
- TTFB > 800 ms on decent hosting → OPcache, PHP version, overloaded shared server.
- Third parties (chat, reCAPTCHA, GTM) block the main thread — trim in GTM, not in the SEO plugin.
- CDN or WAF serves a stale image — hosting ticket, not Puluno Apply.