JavaScript Performance · AuditJet Glossary

Code Splitting

A technique that splits JavaScript bundles into smaller chunks that are loaded on demand rather than all at once.

Code splitting reduces the initial JavaScript payload that must be parsed and executed before a page becomes interactive. In Next.js, React, and Vue, dynamic imports (import()) enable component-level code splitting. Reducing initial JS payload directly improves TBT and INP — less JavaScript executed on load means fewer long tasks.

Related terms

TBT (Total Blocking Time)

The total time between First Contentful Paint and Time to Interactive during which the main thread was blocked for long enough to prevent input responsiveness.

INP (Interaction to Next Paint)

A Core Web Vital that assesses overall responsiveness by observing the latency of all qualifying interactions throughout the entire page lifecycle and reporting the worst-case value.

Tree Shaking

A dead code elimination technique used by JavaScript bundlers to remove unused exports from the final bundle.

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