Core Web Vitals on Shopify in 2026: What Actually Moves the Needle

Interaction to Next Paint (INP) has fully replaced First Input Delay in Google's Core Web Vitals, and it's exposed a problem most Shopify stores have been quietly accumulating for years: third-party app scripts that block the main thread.

In our audits across 40+ stores this quarter, the single biggest INP offender wasn't theme code — it was review apps, upsell widgets, and tracking pixels loading synchronously on every page, regardless of whether they were needed.

The fix isn't removing every app. It's auditing what fires on load versus on interaction, deferring non-critical scripts, and in several cases, replacing bloated all-in-one apps with lighter single-purpose alternatives.

LCP issues, on the other hand, are still overwhelmingly an image problem — oversized hero images and product photos served without proper responsive sizing or modern formats like WebP/AVIF.