This is neither CrUX nor Lighthouse
CrUX is Chrome field data in Search Console / PSI. Lighthouse is a synthetic browser. SiteRune is one server-side GET. We will not print an LCP number we did not measure.
Fetch signals, not a filmstrip
Website Performance Audit
SiteRune measures the document a crawler gets: time to first byte from this vantage point, whether the HTML is compressed and cacheable, and how much script and image weight is in the first response. It does not execute Chrome.
No card. Three guest scans, then an account.
- Multi-page walk
- CMS fingerprint
- Ship-ready files
- How we score
Performance checks we run
- TTFB of the HTML fetch (critical above ~1.8s, high above ~800ms)
- HTML document byte size
- Content-Encoding: gzip / br / zstd
- Cache-Control / CDN-Cache-Control on the document (no-store and private fail public pages)
- External script count and obvious third-party hosts
- Image formats that are still heavyweight JPEGs/PNGs in the HTML
- Inner-page TTFB drift when walked URLs are much slower than home
Field data vs lab data vs this fetch
no-store on the marketing homepage
Usually a CMS 'disable cache for editors' leftover or a Next.js cookies() call in the root layout. TTFB never recovers until the document can sit at the CDN.
WordPress: page builder on every request
The fix is full-page cache (LiteSpeed / APO) and fewer widgets — not a new hero animation.
How to use the numbers
- If TTFB is 2s here, a filmstrip is a funeral. Cache the document first.
- Then run Lighthouse or WebPageTest on the money URL for LCP/INP/CLS.
- Rescan SiteRune after the Cache-Control change. The chapter should move.
Implementation, not slogans
- Fixes are stack-specific: Redis + LiteSpeed on WordPress, ISR/PPR or CDN cache on Next, remove unused Shopify apps, proxy in front of hosted builders.
- We do not block third parties in a browser, so we cannot show a 'what if we removed GTM' filmstrip.
Questions
Do you measure Core Web Vitals?
No. We measure HTML TTFB and document heuristics. Use PageSpeed Insights for lab + field CWV after you ship cache and image fixes.
Why is TTFB different from my RUM?
Different vantage point, different cache warmth, different User-Agent. Treat our number as 'what a cold crawler saw just now'.
Scan a live URL
Same engine as the rest of SiteRune. Guest scans stay free.