What Is Lighthouse?
Lighthouse is a free, open-source auditing tool developed by Google's Chrome team. It loads a page under controlled conditions, measures it and scores it from 0 to 100 in four areas: performance, accessibility, best practices and SEO. Scores of 90 and above show in green, 50 to 89 in orange and anything lower in red.
The performance score combines several measurements. The main ones are when the largest piece of content appears (Largest Contentful Paint), how long the page is too busy to respond (Total Blocking Time) and how much things jump around while loading (Cumulative Layout Shift). For each issue, Lighthouse explains what is wrong and suggests a fix, from oversized images to missing image descriptions.
Lighthouse can be run from Chrome's developer tools, from the command line or automatically with Lighthouse CI, and PageSpeed Insights uses it for its lab results. Each result reflects a single test load on a simulated device and connection, so scores can vary from one run to the next; we read them as a range rather than a single number.
Where We Use Lighthouse
Lighthouse is part of every web project we build, especially at these points:
Pre-Launch Checks
Before launch we audit the main page templates on mobile and desktop and fix whatever comes up: images that are too large, files that hold up rendering, buttons without labels.
Accessibility Audits
Lighthouse checks color contrast, alternative text, form labels and heading order. Automated checks catch only some issues, so we also test with a keyboard and a screen reader.
Technical SEO Checks
It confirms that pages have a description for search results, that links can be crawled, that nothing accidentally blocks a page from search and that the hreflang links between language versions are valid.
Checks After Changes
After a big update, such as a new section or a new tracking code, we run it again and compare. On larger projects it can run automatically with every update, so a slowdown is caught before it goes live.
Why Lighthouse?
A Concrete To-Do List
It doesn't just give a score; it points to the file or element behind each problem, so the fixes are specific.
Four Angles in One Report
Speed, accessibility, sound technical practice and SEO are checked in a single run, so we can see that improving one doesn't quietly harm another.
Open and Repeatable
It's free and open source and runs in any Chrome browser, so you can check our results yourself at any time.
How We Work on Your Project
We run Lighthouse regularly while the design is being turned into code, so problems are caught while they're still small. Before launch we measure the main templates on mobile and desktop several times and look at the typical result rather than a single run.
Before handover we report the scores for all four areas together with the PageSpeed Insights results, and explain plainly any small warnings that remain and why. After launch we repeat the audit whenever a significant change is made.
