Most Shopify LCP problems are apps you installed last quarter
3 URLs, no card.
Shopify's baseline theme can pass vitals. The live shop often does not, because each app adds a script. Reviews, upsells, popups, heatmaps, three pixels "just in case". None of them thinks about LCP.
Measure production, not the theme editor
The editor is not the shopper path. Collect LCP, INP and CLS on the published homepage, a collection, a product and checkout (as far as you can without placing an order).
Usual culprits
- Hero slideshows with uncompressed PNG slides
- App-loaded fonts on top of the theme font
- Review widgets that shift the buy box (CLS)
- Filters that take 300ms of main thread (INP)
- Instant third-party video embeds in the first screen
How to change it
Remove one app at a time on a preview theme and re-measure. Keep the ones that earn money. Replace slideshows with a single sized image. Preload that image. Lazy-load everything below the fold.
FAQ
Does Shopify Plus fix vitals?
Plus gives you more checkout control. It does not delete app scripts on the storefront.
Can I monitor checkout?
You can monitor the URL. Some checkout steps need a session. Treat cart and product as the practical early warning.