Engine Performance & Tuning Flashcards

Which technique reduces the size of JavaScript files by removing whitespace, comments, and shortening variable names?

Answer: Minification

Minification strips non-essential characters from code without changing functionality, reducing file size and transfer time.

A page has a large hero image that is the LCP element. Which optimization MOST directly improves LCP for this element?

Answer: Using fetchpriority="high" on the image tag

fetchpriority="high" tells the browser to prioritize fetching the LCP image earlier, directly reducing LCP time.

What is 'tree shaking' in the context of web performance optimization?

Answer: Eliminating dead code from JavaScript bundles during build

Tree shaking is a build-time technique that removes unused JavaScript exports from bundles, reducing overall bundle size.

Which server-side compression algorithm is widely supported and typically reduces HTML/CSS/JS file sizes by 70–80%?

Answer: GZIP

GZIP is universally supported across browsers and servers and typically achieves 70–80% compression for text-based assets.

What does a low 'unused JavaScript' metric in Lighthouse indicate about a site's performance?

Answer: The site is loading scripts that are never executed on page load

Unused JavaScript means bytes are downloaded, parsed, and compiled unnecessarily, wasting bandwidth and CPU time on page load.

Which technique splits a large JavaScript bundle into smaller chunks loaded only when needed?

Answer: Code splitting

Code splitting divides JavaScript bundles so only the code needed for the current route/interaction is loaded initially.

When analyzing a waterfall chart in Chrome DevTools, a long green bar for a resource indicates:

Answer: Large file download time

In Chrome's network waterfall, the green portion represents content download time, so a long green bar means a large or slow-transferring file.