Free tool
Page Speed Analyzer + Fix Generator
Enter your Core Web Vitals (LCP, INP, CLS, bundle size, image weight) and get a prioritised, copy-paste fix list for your store.
Your current numbers
Read these from a Lighthouse run on the page you want to fix (DevTools › Lighthouse, mobile profile, slow 4G).
0 of 3 vitals passing
LCP
3.4s
Fail · ≤ 2.5s
INP
240ms
Fail · ≤ 200ms
CLS
0.18
Fail · ≤ 0.10
Failing: LCP 3.4s, INP 240ms, CLS 0.18. The ranked fixes below address each failing metric in priority order.
Prioritised fixes (7)
Diagnostic only — numbers are heuristic; re-run Lighthouse after each fix. The 2026 site-wide INP score means a single slow component drags the whole domain, so prioritise INP fixes that touch the highest-traffic templates.
What this does
Enter your current Core Web Vitals and the analyzer returns a ranked fix list with copy-paste snippets. Fixes are ordered by impact, so you work on the metric that actually moves first.
How to get your numbers
Run Lighthouse in Chrome DevTools (F12, then the Lighthouse tab), mobile profile, slow 4G throttling. Then read off:
- LCP, INP, CLS, at the top of the report
- JS bundle and image weight, in the Network panel
- Render-blocking scripts, flagged in the report
Use mobile and slow 4G because that mirrors how Google's field data weights things.
Fix INP first on cart and checkout
Since March 2026, INP is scored site-wide, not page-by-page. One slow template (often cart, checkout, or account) can drag your whole domain's score down.
So even if your LCP is fine, prioritise INP fixes on those pages. More detail in Site-wide CWV scoring.
How to read the verdict
- No failing metrics, 0-1 fixes: you are in good shape. Move effort to other CRO work.
- 1-2 failing metrics, 2-3 fixes: a common starting point. Expect a few focused weeks to reach all-pass.
- 3 failing metrics, 4+ fixes: fix the binding metric (usually INP) first, then re-measure. Some other issues often clear up on their own.
Apply one fix at a time, then re-measure and re-run.
What it cannot do
- It does not read your live page, so it infers priority from the numbers you enter.
- It does not cover slow third-party tags or server response time. If TTFB is over 600 ms, fix the server first.
What to do next
- Run Lighthouse on mobile slow 4G and record LCP, INP, CLS, bundle and image weight.
- Enter the numbers above and review the ranked fixes.
- Apply the top fix, redeploy, and re-run Lighthouse.
- If the metric improved, re-run the analyzer and take the next fix. If not, find the real root cause before moving on.
- Repeat until all three pass, then add Lighthouse CI to catch regressions.
The full discipline lives in the Frontend Performance guide.
Further reading
Frequently asked questions
Chrome DevTools Lighthouse, mobile profile, slow 4G throttling. Headline metrics at the top; bundle/image sizes in Network panel.