Performance auditing with Lighthouse in Astro

Introduction

Lighthouse helps you check how fast and user-friendly your Astro website is. It shows what to fix to make your site better.

You want to see how quickly your Astro site loads on phones and computers.

You need to find ways to improve your website's speed and user experience.

Before launching your Astro site, you want to make sure it works well for everyone.

You want to check if your site is accessible to all users, including those with disabilities.

Syntax

Astro

lighthouse <URL> --output html --output-path ./report.html

Run this command in your terminal to audit your live Astro site by replacing with your site address.

The report.html file will show detailed results you can open in a browser.

Examples

This runs Lighthouse on your Astro site and saves the report as astro-report.html.

Astro

lighthouse https://example-astro-site.com --output html --output-path ./astro-report.html

This audits your local Astro development server and saves results in JSON format.

Astro

lighthouse http://localhost:3000 --output json --output-path ./local-report.json

Sample Program

This Node.js script runs Lighthouse on your Astro site URL and saves the report as an HTML file. It logs success or errors in the console.

Astro

import { exec } from 'node:child_process';

const url = 'https://example-astro-site.com';
const command = `lighthouse ${url} --output html --output-path ./astro-report.html`;

exec(command, (error, stdout, stderr) => {
  if (error) {
    console.error(`Error running Lighthouse: ${error.message}`);
    return;
  }
  console.log('Lighthouse audit completed. Report saved as astro-report.html');
});

Important Notes

Make sure you have Lighthouse installed globally with npm install -g lighthouse before running commands.

Run audits on a stable internet connection for accurate results.

Open the generated HTML report in a browser to see detailed suggestions and scores.

Summary

Lighthouse helps you find ways to improve your Astro site's speed and usability.

Run Lighthouse from the command line with your site URL to get a detailed report.

Use the report to fix issues and make your site better for all users.

Practice

1. What is the main purpose of using Lighthouse with an Astro site?

easy

A. To check and improve the site's performance and usability

B. To write new Astro components automatically

C. To deploy the Astro site to a server

D. To convert Astro code into plain HTML

Solution

1. Step 1: Understand Lighthouse's role

   Lighthouse is a tool designed to analyze websites and provide reports on performance, accessibility, SEO, and best practices.

2. Step 2: Relate to Astro site improvement

   Using Lighthouse on an Astro site helps find ways to improve speed and usability, making the site better for users.

3. Final Answer:

   To check and improve the site's performance and usability -> Option A

4. Quick Check:

   Lighthouse purpose = Performance & usability check [OK]

Hint: Lighthouse audits site quality, not code writing or deployment [OK]

Common Mistakes:

• Thinking Lighthouse writes code
• Confusing Lighthouse with deployment tools
• Assuming Lighthouse converts code formats

2. Which command correctly runs Lighthouse from the command line for the URL https://example.com?

easy

A. start lighthouse --url https://example.com

B. run lighthouse https://example.com

C. lighthouse https://example.com

D. lighthouse run https://example.com

Solution

1. Step 1: Recall Lighthouse CLI syntax

   The basic command to run Lighthouse is simply lighthouse followed by the URL.

2. Step 2: Match the correct syntax

   lighthouse https://example.com matches the correct syntax: lighthouse https://example.com. Other options add unnecessary words or flags.

3. Final Answer:

   lighthouse https://example.com -> Option C

4. Quick Check:

   Correct CLI syntax = lighthouse URL [OK]

Hint: Use just 'lighthouse' plus URL to run audit [OK]

Common Mistakes:

• Adding extra words like 'run' or 'start'
• Using incorrect flags or options
• Confusing command order

3. After running Lighthouse on your Astro site, you see a low score in the 'Performance' category. What is the most likely cause?

medium

A. The site is missing a favicon

B. The site uses too many Astro components

C. The site has no SEO metadata

D. The site has large images and slow loading scripts

Solution

1. Step 1: Understand what affects Performance score

   Performance issues usually come from slow loading resources like large images or heavy scripts.

2. Step 2: Eliminate unrelated options

   SEO metadata and favicon affect SEO or appearance, not performance. Number of Astro components alone doesn't cause low performance.

3. Final Answer:

   The site has large images and slow loading scripts -> Option D

4. Quick Check:

   Performance issues = large images or slow scripts [OK]

Hint: Performance drops mainly due to heavy resources [OK]

Common Mistakes:

• Confusing SEO issues with performance
• Blaming Astro components count directly
• Ignoring resource sizes

4. You ran Lighthouse but the report shows no data and an error message. What is the most likely mistake?

medium

A. You ran Lighthouse without specifying a URL

B. You ran Lighthouse on a local file without a server

C. You forgot to install Astro globally

D. You used an outdated version of Node.js

Solution

1. Step 1: Identify why Lighthouse shows no data

   Lighthouse needs a live URL to audit. Running it on a local file without a server means no data can be fetched.

2. Step 2: Check other options

   Not specifying a URL would cause a command error, not a no data report. Astro installation or Node.js version do not directly cause this error.

3. Final Answer:

   You ran Lighthouse on a local file without a server -> Option B

4. Quick Check:

   Lighthouse needs live URL, not local file [OK]

Hint: Always run Lighthouse on a live server URL, not local files [OK]

Common Mistakes:

• Running Lighthouse on local files without server
• Ignoring error messages about URL
• Assuming Astro install affects Lighthouse

5. You want to improve your Astro site's Lighthouse performance score. Which combination of actions is best?

hard

A. Optimize images, lazy-load components, and reduce JavaScript size

B. Add more Astro components and increase CSS animations

C. Remove all images and use only text content

D. Disable Lighthouse caching and run audits repeatedly

Solution

1. Step 1: Identify actions that improve performance

   Optimizing images reduces load time, lazy-loading defers offscreen content, and reducing JS size speeds up scripts.

2. Step 2: Evaluate other options

   Adding components or animations can slow performance. Removing all images is impractical. Disabling caching doesn't improve site speed.

3. Final Answer:

   Optimize images, lazy-load components, and reduce JavaScript size -> Option A

4. Quick Check:

   Best performance = optimize images + lazy-load + reduce JS [OK]

Hint: Focus on image size, lazy loading, and JS reduction [OK]

Common Mistakes:

• Thinking more components always help
• Removing images entirely
• Misunderstanding caching effects