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Excessive or unused initial JavaScript
One large JS bundle ships to every page, loading code that is never used on that view.
What it means
One large JS bundle ships to every page, loading code that is never used on that view.
Why it happens on Shopify
No code splitting in the custom stack; heavy Shopify themes may ship unused JS.
How to check if you have this issue
Measure transferred bytes, executed code and long tasks on key pages. Separate raw and compressed sizes. Coverage only describes the recorded journey, not all possible use.
How to fix it: precise steps
Isolate optional features, load modules when needed and remove genuinely unused dependencies. Set a site-specific budget rather than a universal SEO threshold. Check first-interaction latency afterwards.
How to confirm it is fixed
Repeat the same checks as in the verification step after deploy. SEO effects can take days to weeks depending on crawl budget.
Impact on SEO and conversion
High-impact issues often hurt perceived performance or SEO consistency; fixes gradually improve rankings and conversion.
Related issues
Sources and editorial context
Teo Comyn · Updated
Technical references consulted for this revision. Illustrative examples are not measured client results. Check the current documentation and your store before applying a change.
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