/ Getting started2 min read
Diagnose your store
Find the real PDP bottleneck before you start changing code.
Use this tool to check your store
The first thing we need to do - figure out how slow our store is, and which metrics are failing.
In site speed, we generally go by 3 main metrics.
- LCP (page slowness to load)
- INP (page lag on interaction)
- CLS (page jumpiness when loading)
These are the 'core web vitals' popularised by Google.
This tutorial will not be covering CLS because there is no research connecting CLS to revenue. CLS is an uncomfortable experience for users, but generally by fixing LCP - you can remove most CLS. I advise not focusing on this until after completing these tutorials.
Shopify Research, April 2026
LCP
- for every 0.1s LCP, CVR drops 3.5%
- recommended LCP: < 2.5s
INP
- for every 32ms INP, CVR drops 1.5%
- recommended INP: < 200ms
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