Released a few months ago now, Lighthouse is an SEO and technical tool available as a Google Chrome extension. It provides all sorts of information about a page, such as load time, SEO optimisation and much more. Do you use it? Can we call it a complete tool?
An interesting diagnosis
To write this article, we used an anonymous website so we could analyse the tool’s components factually. The images below show the results of that analysis. Lighthouse splits its audit into five areas: Performance, Progressive Web App, Accessibility, Best Practices and SEO. At the very top of the generator you can see a score out of 100 awarded to each of these areas. These indicators give an overall impression of the site’s quality.
Media to re-attach: the original French article includes several screenshots of the Lighthouse report (the overall scores and each audit section). They were lost when the content was extracted and must be copied over from the French version before publication.
In the Performance section (above), you first find the same metrics as in PageSpeed Insights (notably First Contentful Paint), as well as the DOM load time and how it evolves, plus an assessment based on that load time. One word of caution, though: this data is collected over a mobile 3G connection, which means the figures shown are valid for a fairly slow connection. So you should not rely on these indications alone during your technical audits — go further.
This section lists the items to optimise in order to improve your site’s speed. You will find, for example, the size of the DOM or image optimisation. As for the qualitative report, colour-coded indicators show how well optimised an element is, even if the list is incomplete: some fundamentals are still missing, such as JS/CSS compilation.
One rather interesting addition: the algorithm checks whether the site is optimised for Progressive Web Apps. The tool compares your site’s data against a list of prerequisites a site must meet to install a PWA — load speed, use of HTTPS, and so on.
Something you would not necessarily expect in a technical/SEO audit: accessibility. Do your images have alt attributes? Have you labelled your buttons and CTAs? That is what Lighthouse analyses on your site in order to judge whether it is accessible. The aim is to make your site usable by everyone.
The audit continues with a top four of best practices to adopt on your site, such as using HTTPS or displaying your browser errors in the console. This section assesses whether your site respects the fundamental principles of website creation.
Finally, an SEO section. For reasons of anonymity, we are not giving details of the audits of the site shown in the screenshots. You will mainly find technical data such as metadata optimisation or mobile compatibility, rather than more complex factors such as netlinking or the site’s internal and external link structure.
So what should we make of this tool? After a factual analysis, it has both strengths and weaknesses.
On the positive side, there is a broad selection of technical data: the tool does not stop at the DOM load speed, it surfaces plenty of other interesting elements. Also on the plus side, the Progressive Web App optimisation shows that the tool keeps up with the times, as does the presence of accessibility checks, which remain rare in most tools.
On the negative side, the site is only tested over a 3G connection, so the data shown is only valid for average to weak connections. It is also fair to say that the data displayed could just as easily be found in the Chrome logs without using any tool. And finally, the most disappointing part is the SEO analysis, which is limited to metadata alone.
In conclusion, this tool does the job as long as you only want to analyse your site’s code: the data Lighthouse provides is useful and deserves a place in your audits. If, on the other hand, you work in SEO, you will need to combine this data with that of a semantic and authority analysis tool such as Semrush or Majestic SEO.
Note for the English version: this 2018 review is now out of date. Lighthouse’s Progressive Web App category was removed, the default network throttling simulates slow 4G rather than 3G, the Performance metrics are now built around the Core Web Vitals, and the tool is available in Chrome DevTools, PageSpeed Insights and the CLI rather than only as an extension. A refresh is recommended before publishing the English version.
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