Exploring Google Lighthouse: A Comprehensive Guide to Maximizing Its Utility

Lighthouse, a Google-backed open-source tool, delves into the performance analysis of web pages, with a primary emphasis on web applications and mobile sites. Despite its specific focus, it furnishes valuable insights and recommendations applicable to enhancing any website.

Prioritizing mobile optimization inevitably enhances overall performance even in desktop web browsers. This dual benefit extends advantages to every website developer seeking optimization strategies.

Optimizing Websites in the Google Era

While Google’s primary emphasis has historically centered on search, they have concurrently developed tools to assist website owners in enhancing both performance and indexability over the years.

You might be familiar with their Mobile-Friendly Test or Test My Site applications, and personally, I find the Structured Data Testing Tool among the most valuable in Google’s SEO toolkit.

If you haven’t explored these resources yet, it’s worth taking the time to do so. Brace yourself for a plethora of improvement suggestions, though.

The abundance of information these tools provide can be overwhelming. However, by systematically addressing one issue at a time, you can gradually ascend the mountain of website performance enhancements.

What Is Google Lighthouse?

Lighthouse functions as an application that conducts an in-depth examination, referred to as an “audit,” running a battery of tests to scrutinize information on a web application or website page. Subsequently, it generates a comprehensive report detailing the app or page’s performance.

During the audit, the application undergoes testing by loading the page under conditions simulating a weak 3G connection, utilizing a sluggish device. This simulation introduces elements like packet or data loss, network limitations, and CPU throttling.

Essentially, Lighthouse assesses the page as it might appear to someone using an older phone with a less-than-optimal connection. While this may seem challenging for any page, the objective is to enhance speed. The rationale is that by improving speed under strenuous conditions, the overall performance significantly advances, even on a swift device connected to a high-speed network.

Interpreting the results of a page audit, a score falling within 90-100 indicates commendable performance. Scores ranging from 50-89 are considered average, while a score of 0-49 categorizes as poor. According to Google, any score surpassing 90 positions the website in the top 5% of well-functioning websites.

What Metrics Does Lighthouse Assess?


Emphasizing the significance of perceived speed alongside actual speed, the Lighthouse report concentrates on various aspects related to swiftly displaying content on the screen and testing user interaction capabilities. Key elements within the Performance section include:

  1. First Contentful Paint: Measures the time it takes for any content to appear onscreen.
  2. First Meaningful Paint: Indicates how quickly meaningful content appears, with a lower score indicating faster page display.
  3. Speed Index: Evaluates how rapidly a page’s contents become viewable, with an index target under 1.25 seconds.
  4. First CPU Idle: Marks the point when the device ceases rendering the page.
  5. Time to Interactive: Measures when a page becomes interactive, indicating when user interface elements respond to input.
  6. Estimated Input Latency: Evaluates how quickly a page responds to user input, with a target latency of less than 50 milliseconds.


The Accessibility section checks for page heading, contrast between background and foreground colors, document title tag, link names, and viewer-scalable viewport. It also provides a list of “Additional items to manually check” due to the impossibility of automating all relevant benchmarks.

Best Practices

Examining HTTPS, application cache, cross-origin link safety, geolocation permission requests, vulnerable JavaScript libraries, deprecated APIs, and the ability to paste into password fields, the Best Practices section ensures compliance. It also considers correct aspect ratio display for images.


With roots in Google, Lighthouse includes basic SEO information and recommendations, focusing on page tags and status codes. While not a strict SEO tool, future expansions in SEO checks are anticipated. The SEO section suggests additional manual checks, currently linking to the Structured Data Testing Tool.

Progressive Web App

In regular web page audits, most results in the Progressive Web App section may not apply. However, relevant checks include:

  1. Mobile Network Page Load Speed: Ensures the page loads quickly on mobile networks.
  2. Viewport-Sized Content: Verifies content is appropriately sized for the viewport.
  3. Meta Viewport Tag: Checks for the presence of a meta tag with width or initial-scale.
  4. JavaScript-Independent Content: Assesses content availability when JavaScript is disabled.

Harnessing the Power of Lighthouse

Now that you’re acquainted with Lighthouse’s capabilities, you might be eager to put it to the test.

For Google Chrome users, Lighthouse is readily available in the Audits tab within DevTools. If navigating through the Chrome DevTools feels like navigating a maze (understandably so!), consider simplifying the process by installing the Lighthouse Chrome extension.

However, if Chrome isn’t your browser of choice, fear not. You can still leverage Lighthouse’s capabilities. A Node command line version is available for those inclined towards command-line interfaces. Alternatively, you can access most Lighthouse tools by visiting the PageSpeed Insights site.

It’s essential to note that Lighthouse operates on a page-by-page basis, conducting audits individually rather than crawling and auditing multiple pages across a site. Despite this, numerous aspects of the Lighthouse report address issues that likely extend site-wide, such as render-blocking JavaScript.

While a single-page audit can yield valuable insights, it’s advisable to test distinct sections of your site separately if there are marked differences, such as a blog or forum alongside static pages. This approach ensures that optimization steps can be tailored to each section, addressing specific needs that may vary across different parts of your website.

Examining a Webpage with Lighthouse

Using the Chrome Extension:

  1. Install the Lighthouse Chrome Extension.
  2. Open the desired page in the Chrome browser.
  3. Click on the Lighthouse icon adjacent to the Chrome address bar.
  4. Select the “Generate report” button.
  5. Witness Lighthouse executing its audits and presenting the report in a new tab.

Accessing Lighthouse in Chrome DevTools:

  1. Open the page you wish to audit in the Chrome browser.
  2. Launch Chrome DevTools:
    • Windows: F12 key or Control+Shift+I
    • Mac: Command+Option+I
    • From Chrome’s main menu: Click “Customize and control Google Chrome” in the upper right corner, then choose More Tools > Developer Tools.
  3. Navigate to the Audits tab.
  4. Click on the “Run audits” button.
  5. Observe Lighthouse in action, conducting its audits and showcasing the report within the DevTools pane or window.

Leveraging Lighthouse for Enhanced Performance Optimization

In the realm of website optimization, a proactive approach to enhancing performance provides a distinct advantage. Fortunately, Google offers a plethora of tools to simplify this task, and Lighthouse stands out among them.

For those ready to invest the time and effort required for continuous website improvement, the possibilities are limitless.



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