JavaScript file too large

Shipping too much JavaScript is one of the most common causes of slow pages and poor responsiveness.

What it is

This check flags scripts whose transferred size exceeds a healthy budget, often a single monolithic bundle.

Why it matters for SEO

Large bundles delay parsing and execution, hurting Interaction to Next Paint and Largest Contentful Paint.

Example

bundle.js - 1.8 MB transferred

How to fix

1. Code-split and lazy-load non-critical scripts.
2. Tree-shake unused code and drop heavy dependencies.
3. Minify and serve compressed (brotli/gzip) bundles.
4. Re-crawl to confirm script weight dropped.

Related checks

• Page has broken JavaScript
• Page has redirected JavaScript

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