Lighthouse Performance Audits: Tips for Scoring 100 on Your Next Site Review

Key Takeaways

• First Contentful Paint (FCP) should be under 2 seconds to score well.
• Eliminate render-blocking resources to improve page load times.
• Optimize images by using the right formats and sizes.
• Ensure all interactive elements are keyboard accessible.
• Use HTTPS and remove any vulnerable libraries for better security.

Getting Started with Lighthouse

Google Lighthouse is an open-source tool that helps you improve the quality of your web pages. It audits your site for performance, accessibility, SEO, and best practices. The goal is to provide you with actionable insights to enhance your website’s overall user experience.

To start, you’ll need Google Chrome installed on your computer. Lighthouse is built into Chrome’s Developer Tools, making it easily accessible.

Setting Up a Lighthouse Audit

First, open Google Chrome and navigate to the web page you want to audit. Right-click anywhere on the page and select “Inspect” to open Developer Tools. Once the Developer Tools panel is open, click on the “Lighthouse” tab.

You’ll see various audit options like Performance, Accessibility, Best Practices, and SEO. For a comprehensive review, select all the categories. Click the “Generate report” button to start the audit.

Running a Lighthouse Audit

When you click “Generate report,” Lighthouse will simulate a user visiting your page and run various tests. This process may take a few minutes, depending on your site’s complexity. Once completed, Lighthouse will display a detailed report with scores for each category.

The report will highlight areas needing improvement and provide suggestions for optimizing your site. Now, let’s dive into optimizing your performance scores.

Optimizing Performance Scores

Improving Load Times

One of the most critical aspects of performance is load time. A fast-loading site provides a better user experience and can significantly impact your Lighthouse score. Here are some strategies to improve your load times:

Minimize Render Blocking Resources

Render-blocking resources, like JavaScript and CSS files, can delay your page’s loading. To minimize these, you can:

• Defer non-critical JavaScript.
• Inline critical CSS.
• Use asynchronous loading for JavaScript files.

Optimize Image Sizes

Large, unoptimized images can slow down your site significantly. Use the following tips to optimize your images:

• Choose the right image format (e.g., JPEG for photos, PNG for graphics).
• Compress images without sacrificing quality.
• Use responsive images to serve the appropriate size based on the user’s device.

Defer Offscreen Images

Images that are not immediately visible when the page loads should be deferred. This means loading them only when they come into the viewport. You can achieve this by implementing lazy loading.

Reducing JavaScript and CSS

Excessive JavaScript and CSS can bloat your site and slow it down. Reduce the amount of code by:

• Removing unused JavaScript and CSS.
• Minifying your JavaScript and CSS files.
• Combining multiple CSS files into one.

Minify CSS and JavaScript

Minification removes unnecessary characters from your code without changing its functionality. This can significantly reduce file sizes and improve load times. Use tools like UglifyJS for JavaScript and CSSNano for CSS to automate this process.

Remove Unused CSS

Unused CSS can accumulate over time, especially if your site undergoes frequent updates. Use tools like PurifyCSS or UnCSS to identify and remove unused styles, making your CSS files leaner and more efficient.

Boosting Accessibility Scores

Accessibility ensures that all users, including those with disabilities, can navigate and interact with your site. A high accessibility score not only improves user experience but also broadens your audience reach.

Ensure Text Readability

Text readability is crucial for accessibility. Ensure your text is legible by:

• Using a font size of at least 16px.
• Maintaining a high contrast between text and background.
• Avoiding overly decorative fonts that can be hard to read.

Keyboard Accessibility

All interactive elements on your site should be accessible via keyboard. This includes links, buttons, and form fields. Ensure that:

• All elements have a visible focus state.
• Users can navigate through your site using the Tab key.
• Interactive elements are reachable and operable via keyboard.

Remove Unused CSS

Unused CSS can accumulate over time, especially if your site undergoes frequent updates. Use tools like PurifyCSS or UnCSS to identify and remove unused styles, making your CSS files leaner and more efficient. This not only improves load times but also enhances overall site performance.

Boosting Accessibility Scores

Accessibility ensures that all users, including those with disabilities, can navigate and interact with your site. A high accessibility score not only improves user experience but also broadens your audience reach.

Ensure Text Readability

Text readability is crucial for accessibility. Ensure your text is legible by:

• Using a font size of at least 16px.
• Maintaining a high contrast between text and background.
• Avoiding overly decorative fonts that can be hard to read.

Keyboard Accessibility

All interactive elements on your site should be accessible via keyboard. This includes links, buttons, and form fields. Ensure that:

• All elements have a visible focus state.
• Users can navigate through your site using the Tab key.
• Interactive elements are reachable and operable via keyboard.

Enhancing Best Practices

Adhering to best practices ensures your website is built on modern web development standards. This not only improves performance but also ensures security and reliability.

Security Enhancements

Security is paramount for any website. Ensuring your site is secure can significantly boost your Lighthouse score under best practices.

Use HTTPS

One of the simplest yet most effective ways to enhance your site’s security is by using HTTPS. It encrypts data between the user’s browser and your server, protecting sensitive information. Most importantly, browsers like Chrome mark HTTP sites as “Not Secure,” which can deter users.

Remove Vulnerable Libraries

Outdated or vulnerable libraries can be a significant security risk. Regularly audit your site’s libraries and remove or update any that are vulnerable. Tools like Snyk can help you identify these vulnerabilities.

Adopt Modern Web Standards

Using modern web standards ensures your site is fast, secure, and reliable. This includes adopting practices like responsive design, using semantic HTML, and following the latest CSS and JavaScript standards. By doing so, you not only improve your Lighthouse score but also provide a better user experience.

Maximizing SEO Scores

Search Engine Optimization (SEO) is crucial for driving organic traffic to your site. Lighthouse audits your site for SEO best practices, and improving these can significantly boost your site’s visibility on search engines.

Optimize Meta Tags

Meta tags provide search engines with information about your site. Ensure that each page has a unique and descriptive title tag and meta description. Use relevant keywords, but avoid keyword stuffing.

Ensure Mobile-Friendliness

With more users accessing the web via mobile devices, ensuring your site is mobile-friendly is crucial. Use responsive design techniques to ensure your site looks and functions well on all device sizes. Additionally, test your site on various devices to ensure a consistent user experience.

Understanding Lighthouse Score Components

Lighthouse scores are based on several metrics, each contributing to the overall score. Understanding these components can help you prioritize your optimization efforts.

Audit Metrics Breakdown

Lighthouse evaluates your site based on several key metrics:

• First Contentful Paint (FCP): Measures the time it takes for the first piece of content to appear on the screen.
• Speed Index: Shows how quickly the content is visually displayed during page load.
• Largest Contentful Paint (LCP): Measures when the largest content element is visible.
• Total Blocking Time (TBT): Measures the time during which the main thread is blocked and unable to respond to user input.
• Cumulative Layout Shift (CLS): Quantifies how much the page layout shifts during loading.

Weight of Each Metric

Each metric has a specific weight in the overall Lighthouse score:

Metric	Weight
First Contentful Paint (FCP)	10%
Speed Index	10%
Largest Contentful Paint (LCP)	25%
Total Blocking Time (TBT)	30%
Cumulative Layout Shift (CLS)	25%

Tools and Resources for Continuous Improvement

Optimizing your site is an ongoing process. Leveraging the right tools and resources can help you maintain and improve your Lighthouse scores over time.

Useful Chrome Extensions

Several Chrome extensions can aid in your optimization efforts:

• Lighthouse: Run audits directly from your browser.
• Web Vitals: Monitor your site’s Core Web Vitals in real-time.
• AMP Validator: Ensure your AMP pages are valid and optimized.

Online Resources and Communities

Stay updated with the latest web development trends and best practices by engaging with online resources and communities:

• web.dev: Google’s resource for web developers.
• Stack Overflow: Get answers to your technical questions.
• Smashing Magazine: Articles and tutorials on web development and design.

Frequently Asked Questions

What is Lighthouse and how does it work?

Lighthouse is an open-source tool from Google that audits web pages for performance, accessibility, SEO, and best practices. It simulates a user visiting your page and runs various tests to provide actionable insights for optimization.

How often should I run a Lighthouse audit?

Run a Lighthouse audit whenever you make significant changes to your site or at least once a month to monitor performance and identify areas for improvement.

How can I improve my site’s First Contentful Paint (FCP) score?

To improve your FCP score, optimize your server response times, eliminate render-blocking resources, and use efficient caching strategies. Prioritize loading critical content first to ensure it appears quickly.

Is it possible to get a 100 score in all categories?

Achieving a perfect score in all categories is challenging but possible. Focus on continuous improvement and regularly audit your site to identify and address issues promptly.

Can Lighthouse help with eCommerce site optimization?

Yes, Lighthouse is beneficial for eCommerce sites. It helps identify performance bottlenecks, improve user experience, and enhance SEO, which can lead to higher conversion rates and better search engine rankings.

Audit Metrics Breakdown

Lighthouse evaluates your site based on several key metrics:

• First Contentful Paint (FCP): Measures the time it takes for the first piece of content to appear on the screen.
• Speed Index: Shows how quickly the content is visually displayed during page load.
• Largest Contentful Paint (LCP): Measures when the largest content element is visible.
• Total Blocking Time (TBT): Measures the time during which the main thread is blocked and unable to respond to user input.
• Cumulative Layout Shift (CLS): Quantifies how much the page layout shifts during loading.

Weight of Each Metric

Each metric has a specific weight in the overall Lighthouse score:

Metric	Weight
First Contentful Paint (FCP)	10%
Speed Index	10%
Largest Contentful Paint (LCP)	25%
Total Blocking Time (TBT)	30%
Cumulative Layout Shift (CLS)	25%

Tools and Resources for Continuous Improvement

Optimizing your site is an ongoing process. Leveraging the right tools and resources can help you maintain and improve your Lighthouse scores over time.

Useful Chrome Extensions

Several Chrome extensions can aid in your optimization efforts:

• Lighthouse: Run audits directly from your browser.
• Web Vitals: Monitor your site’s Core Web Vitals in real-time.
• AMP Validator: Ensure your AMP pages are valid and optimized.

Online Resources and Communities

Stay updated with the latest web development trends and best practices by engaging with online resources and communities:

• web.dev: Google’s resource for web developers.
• Stack Overflow: Get answers to your technical questions.
• Smashing Magazine: Articles and tutorials on web development and design.

Frequently Asked Questions

What is Lighthouse and how does it work?

Lighthouse is an open-source tool from Google that audits web pages for performance, accessibility, SEO, and best practices. It simulates a user visiting your page and runs various tests to provide actionable insights for optimization.

How often should I run a Lighthouse audit?

Run a Lighthouse audit whenever you make significant changes to your site or at least once a month to monitor performance and identify areas for improvement.

How can I improve my site’s First Contentful Paint (FCP) score?

To improve your FCP score, optimize your server response times, eliminate render-blocking resources, and use efficient caching strategies. Prioritize loading critical content first to ensure it appears quickly.

Is it possible to get a 100 score in all categories?

Achieving a perfect score in all categories is challenging but possible. Focus on continuous improvement and regularly audit your site to identify and address issues promptly.

Can Lighthouse help with eCommerce site optimization?

Yes, Lighthouse is beneficial for eCommerce sites. It helps identify performance bottlenecks, improve user experience, and enhance SEO, which can lead to higher conversion rates and better search engine rankings.

With these tips and strategies, you’re well on your way to scoring 100 on your next Lighthouse audit. Continuous monitoring and optimization are key to maintaining a high-performing, accessible, and secure website. Happy auditing!