A Beginner’s Guide to Lighthouse

You’ve constructed an internet site, however how nicely does it carry out on your finish customers? It’s essential to ask this query, however how are you going to get solutions? One glorious choice is to use Lighthouse.

Lighthouse permits you to simply and routinely analyze an internet web page’s efficiency and high quality. It offers instruments that allow you to perceive how to enhance your net web page’s efficiency, accessibility, web optimization and extra. Using these scores to improve your web site will in the end lead to attracting extra customers and rising your web site’s rank in search engines like google.

In this text, we’ll discover the significance of web site efficiency, which is the spotlight of Lighthouse’s scoring. We’ll additionally have a look at why we must always use Lighthouse; how to use Lighthouse, each by way of Chrome and by way of the Lighthouse CLI; and the assorted audits Lighthouse can carry out to rating your net web page, and why they’re vital. We’ll additionally cowl how some frequent efficiency and different web site points may be resolved.

We’ll additionally have a look at how to use WebPageTest, one other highly effective device for assessing website efficiency.

Why Performance Is Important

If you have a look at a few of the world’s finest web sites, all of them have one factor in frequent: they supply their customers with a superior expertise. There are many causes for this, however one of the vital vital ones is efficiency. Users love a quick web site. The longer they’ve to watch for an internet site to load, the extra doubtless they’ll depart the web site looking for a greater one that enables them to do what they want to do with out the wait.

Improving your web site’s efficiency can lead to the next web optimization rating (as we’ll see in additional particulars later within the article), and a lift in click-through and conversion charges. So, in order for you extra gross sales, sign-ups, or visitors, you’ll first have to make sure that your web site’s efficiency is up to scratch.

Why Use Lighthouse

Lighthouse is an open-source device created by Google. As Google is a good firm that’s trusted by many, it makes the outcome extra dependable than different instruments. Furthermore, as Google’s search engine is the main search engine for the past decade, showing larger on their search engine will most certainly lead to extra visitors. So, getting the next rating on their efficiency audit device can probably elevate the rating of your web site of their search outcomes.

But aside from the truth that Lighthouse was created by Google, what makes it a great device is its detailed outcomes which have the consumer’s finest curiosity at coronary heart. Lighthouse offers many outcomes regarding how lengthy it takes the web page to load, if the web page (and in the end the web site) is safe, if the web page’s accessibility practices and implementations enable for inclusivity of all customers, and extra.

How to Use Lighthouse

In this part, we’ll first undergo the best approach to use Lighthouse to analyze and verify the rating of an internet web page, which is completed instantly by Chrome. Then, we’ll verify different Lighthouse instruments which may present much more detailed outcomes or choices.

Using Chrome

Using Lighthouse by Chrome is the best methodology to measure your web site’s efficiency. First, open any net web page that you just’d like to measure. To show, I’ll be utilizing some outcomes from an audit run on my website and on GitHub for us to see quite a lot of pattern outcomes.

Next, open the devtools both by clicking shift + management + J or F12 on Windows/Linux, or choice + command + J or fn + F12 on macOS.

After that, click on on the Lighthouse tab.

As you’ll be able to see, you’ll be able to select which classes you need the audit to embody. These classes are Performance, Progressive Web App, Best Practices, Accessibility, and web optimization. You may also select whether or not you need the audit to run on Mobile or Desktop.

In this part, we’ll carry out 4 audits that are Performance, Best Practices, Accessibility, and web optimization, and we’ll run them on Desktop. However, to obtain optimum outcomes, it’s vital to take a look at your net web page underneath totally different situations — resembling on Mobile and at totally different web speeds.

So, on the net web page you need to measure, go forward and select the 4 classes talked about and Desktop, then click on Generate Report.

Click Generate Report

This can take a couple of minutes, and also you’ll see that your browser’s window would possibly develop and shrink by the method. This is as a result of the report entails totally different display screen sizes and situations on your net web page. Once it’s achieved, the Lighthouse tab will embody the outcome for the audit, which can embody the rating for every of Performance, Best Practices, Accessibility, and web optimization.

Lighthouse Score

It must be famous that generally the outcomes may be totally different based mostly in your web connection. Also, generally Lighthouse can present a discover that some extensions may need affected the outcome. If so, it’s most likely finest to run the take a look at in an Incognito Window.

When Lighthouse has completed operating, you’ll be able to click on on any of the classes to see a extra detailed report.


Performance focuses on how to make your web site load sooner. We’ll go over the six vital metrics for Performance, what they every entail and the way to obtain a greater rating in every of them.

First Contentful Paint (FCP)

The first contentful paint (FCP) is measured from the second the consumer navigates to the net web page. It measures how lengthy it takes for the primary piece of DOM content material to load. The DOM content material can embody photos, non-white canvas components, and SVG components.

FCP is measured in seconds. In order on your net web page to have a “Green” rating — which implies a quick FCP — the primary piece of DOM content material ought to take at most 1.8 seconds to load. Once it goes above that, it could go to both reasonable or gradual.

The motive FCP is vital goes again to understanding the consumer. As talked about earlier than, customers are impatient and can depart your web site if it takes too lengthy to load. A quick FCP retains customers engaged. It may be one thing so simple as a loading display screen that tells the consumer to hold in tight as a result of the net web page goes to load quickly.

One issue that may have an effect on your web site’s FCP time is fonts. Fonts can take a very long time to load, generally making the textual content invisible till it masses. A great way to resolve that is by utilizing the CSS property font-display: swap; when declaring your font utilizing @font-face. For instance:

@font-face {
    font-family: 'MyFont';
    font-style: regular;
    font-weight: 400; 
    src: url(MyFont.woff);
    font-display: swap;

If you’re utilizing Google Fonts, this property is now enabled by default. This property permits the textual content to seem utilizing the consumer’s system default font till the web site’s font is loaded.

Another issue that impacts your FCP is render-blocking sources. These are normally JavaScript or CSS recordsdata which can be loaded synchronously within the and take a very long time to load. These sources will drive the remainder of the web page to wait till they’re loaded earlier than the web page can totally load, thus affecting the FCP of DOM content material.

Here are some methods you’ll be able to resolve this:

  • Add the defer or async attributes to your