Engine Performance & Tuning Flashcards

Which technique bundles multiple CSS background images into a single file to reduce HTTP requests?

Answer: CSS sprites

CSS sprites combine multiple images into one file, using background-position to display specific portions, reducing HTTP requests.

What does the 'defer' attribute on a script tag do?

Answer: Downloads the script in parallel but executes after HTML parsing

The defer attribute downloads the script without blocking HTML parsing and executes it after the document is fully parsed.

Which Google tool measures real-world Core Web Vitals data from actual Chrome users visiting a site?

Answer: Chrome User Experience Report (CrUX)

CrUX aggregates real-world performance data from opted-in Chrome users and powers the 'field data' shown in PageSpeed Insights.

A CDN (Content Delivery Network) improves SEO performance primarily by:

Answer: Serving assets from edge nodes geographically closer to users

CDNs cache and serve static assets from edge servers near users, reducing latency and improving load times and TTFB.

Which resource hint tells the browser to establish a connection to a third-party origin in advance, including DNS, TCP, and TLS?

Answer: preconnect

Preconnect performs the full connection handshake (DNS + TCP + TLS) in advance, unlike dns-prefetch which only resolves DNS.

Render-blocking resources negatively impact which Core Web Vital MOST directly?

Answer: Largest Contentful Paint (LCP)

Render-blocking CSS and JS delay the browser from rendering content, directly pushing back the LCP element paint time.

What is the recommended maximum LCP (Largest Contentful Paint) threshold for a 'Good' score according to Google?

Answer: 2.5 seconds

Google defines LCP as 'Good' when it occurs within 2.5 seconds; 2.5–4.0s is 'Needs Improvement' and above 4.0s is 'Poor'.