Core Web Vitals optimization using Lighthouse

Understanding Core Web Vitals and Lighthouse

Core Web Vitals, huh? Ever wonder why some websites just feel faster and smoother? Turns out, Google cares about that a lot—and you should too. These vitals are key to a good user experience, which, surprise, also affects your search ranking.

Basically, core web vitals are LCP (Largest Contentful Paint), CLS (Cumulative Layout Shift), and INP (Interaction to Next Paint). They measure loading speed, visual stability, and interactivity. Good scores? good user experience. Bad scores? Users bounce.

• Largest Contentful Paint (LCP): measures how long it takes for the largest element on a page to become visible. It's important for ecommerce sites making sure product images load quickly. A good LCP score is generally under 2.5 seconds, meaning users see the main content without much waiting. Slow LCP can make users think your site is broken or just too slow to bother with.
• Cumulative Layout Shift (CLS): quantifies unexpected layout shifts. Think of a news site where ads cause the text to jump around, really annoying, right? A good CLS score is under 0.1, meaning there's very little unexpected movement on the page. High CLS can lead to users accidentally clicking the wrong thing or losing their place on the page.
• Interaction to Next Paint (INP): measures how responsive a site is to user interactions. For example, if your building a saas platform you need to ensure buttons and forms respond quickly. A good INP score is under 200 milliseconds, indicating that most interactions feel instantaneous. Poor INP means users might feel like your site is laggy or unresponsive, leading to frustration.

Google Lighthouse is your trusty sidekick. It's a free auditing tool that checks performance, accessibility, seo, and more. You can access it right in Chrome DevTools, PageSpeed Insights, or even via the command line. Lighthouse helps measures core web vitals, giving you a performance score and pointing out areas that need improvement. It's like a health check for your website. Getting a good score isn't just about bragging rights; it's about making sure your site is user-friendly and ranks well. So, next up, we'll dive deeper into how Lighthouse does it's thing.

Setting Up and Running a Lighthouse Audit

Ever wondered how to peek under the hood of a website? Lighthouse audits are the key. It's like having a performance detective for your site—but how do you get started?

Here’s how to run a Lighthouse audit right in your browser:

1. Open Your Website in Chrome: Navigate to the web page you want to audit.
2. Open Chrome DevTools: Right-click anywhere on the page and select "Inspect," or press F12 (or Cmd+Option+I on Mac).
3. Navigate to the Lighthouse Tab: In the DevTools panel that appears, look for a tab labeled "Lighthouse." Click on it.
4. Configure Your Audit:
   • Device: Choose whether you want to simulate a mobile or desktop device. Mobile is usually more critical as it often has more constraints.
   • Categories: Select the categories you want Lighthouse to audit. For Core Web Vitals, you'll definitely want to select "Performance." You can also choose others like "Accessibility," "Best Practices," and "SEO" for a more comprehensive review.
5. Generate the Report: Click the "Generate report" button. Lighthouse will then simulate loading your page and analyze it across the selected categories. This might take a minute or two.

Once the audit is complete, Lighthouse will present you with a detailed report. This report includes an overall score for each category and specific recommendations for improvement. The following sections will help you understand and act on these recommendations, especially those related to Core Web Vitals.

Optimizing Largest Contentful Paint (LCP) using Lighthouse

Okay, so you wanna speed up your website? Let's talk about LCP, or Largest Contentful Paint. It's all about making that first impression count.

Lighthouse can really help you pinpoint what's slowing things down. It has this "Largest Contentful Paint element" audit that straight-up tells you what the browser considers the biggest thing it had to load. Is it an image? A big chunk of text? Knowing this is half the battle, really.

• Images are often the culprit. So, for e-commerce sites, its important to ensure product images load quickly. Lighthouse can even give you image optimization tips. This might include:
  • Compressing images: Using tools to reduce file size without a noticeable loss in quality.
  • Using modern image formats: Like WebP, which offers better compression than JPEG or PNG.
  • Implementing lazy loading: This means images only load when they are about to enter the viewport, saving initial load time.
• Text blocks can also be slow. Maybe you're loading in some fancy web fonts, or the server is just taking it's sweet time to deliver the content. To optimize text delivery:
  • Preload critical fonts: Use <link rel="preload"> to tell the browser to fetch essential fonts early.
  • Use font-display: swap: This CSS property allows text to be displayed immediately using a system font while the custom font loads, preventing a blank text period.
  • Improve server response times (TTFB): Ensure your server is configured efficiently and can deliver content quickly.

The key is to find out why it is slow. After you find the problem, you can figure out how to fix it. Next up: Image optimization – a big win for LCP!

Reducing Cumulative Layout Shift (CLS) with Lighthouse

Fighting CLS, or Cumulative Layout Shift, it's like playing whack-a-mole, isn't it? Stuff jumping around on your page after it loads? Super annoying for users and also, uh, not great for your seo.

Lighthouse can help you track down these pesky shifts. Here's how:

• Lighthouse's "Avoid large layout shifts" audit is your starting point. It'll show you the dom elements contributing the most to those annoying page jumps. Kinda like, a CLS leaderboard for your site.
• Understanding your CLS score is key. That score, it's not just a number; it reflects how visually stable your page is. A high score means more shifting going on, which is bad news. Generally, a CLS score below 0.1 is considered good, 0.1 to 0.25 needs improvement, and above 0.25 is poor.
• Visualizing the shifts helps a ton. Tools like SpeedCurve's Core Web Vitals dashboard and Defaced's Layout Shift GIF Generator can show you exactly what's moving and how much. When visualizing, you're looking for elements that jump unexpectedly, especially after the page has seemingly finished loading. For example, you might see an ad pop in and push all the content down, or a font that loads late and causes text to reflow.

For example, a financial news site might see their CLS score tank because of dynamically loading ads that push content around. Or an e-commerce site might get dinged 'cause product images without defined dimensions are causing shifts.

Next, we'll dive into setting dimensions for images and videos to squash some of those shifts.

Improving Interaction to Next Paint (INP) using Lighthouse

Wanna make your website feel faster? Interaction to Next Paint (inp) is the key. It measures how quickly your site responds when someone clicks a button or taps a link. Lighthouse can help you nail it.

• The "Avoid long main-thread tasks" audit in lighthouse it identifies tasks that are bogging things down. Think of it as finding the biggest time wasters on your site. A "long task" is generally considered anything that takes longer than 50 milliseconds to execute on the main thread, as this can cause the browser to become unresponsive.
• Break up those long tasks into smaller, manageable chunks. It's like, instead of one massive job, you're doing a bunch of little ones. Common strategies include:
  • Using setTimeout to break up a long-running loop or computation.
  • Employing requestIdleCallback to schedule less urgent work for when the browser is idle.
• Defer non-critical tasks. If it doesn't need to happen right away, push it back. Non-critical tasks might include things like analytics tracking, complex UI updates that aren't immediately visible, or background data processing. You can defer these using:
  • The async or defer attributes on <script> tags.
  • Code splitting in your JavaScript bundles.

For example, on an e-learning platform, deferring complex calculations until after the user has started interacting can improve responsiveness.

Next up, optimizing JavaScript execution.

Advanced Techniques and Beyond Core Web Vitals

Alright, so you've been tweaking your core web vitals, nice! But, what's next? there is always more to improve.

• Blocking network requests in Chrome DevTools lets you see how much individual resources are impacting performance. Like, if you block that pesky tracking script, how much faster does the site actually get? To do this, open DevTools, go to the "Network" tab, and check the "Disable cache" option. You can then right-click on specific requests and select "Block request URL" to see how removing it affects load times and other metrics.
• Explore other Lighthouse audits beyond just core web vitals. Accessibility, best practices, seo—it's all in there!. It's about making your site good for everyone, not just search engines.
• Field data is very important. Chrome User Experience Report (CrUX) it gives you the real deal, not just lab results. Comparing the two it will give you a complete picture. You can access CrUX data through tools like PageSpeed Insights (which shows CrUX data alongside its lab results) or more advanced methods like Google's BigQuery. Field data shows how real users are experiencing your site, which is crucial because lab data is tested in controlled conditions.

So, keep testing, keep tweaking, and keep making the web a better place, one audit at a time.