Lighthouse is a useful tool that is unfortunately tucked away within depths of the Chrome browser devtools. It performs an audit of a URL that you supply and provides a report based on scoring across five categories; Performance, Progressive Web App (PWA), Accessibility, Best Practices and Search Engine Optimisation (SEO).

The easiest method of taking it for a spin is to start Chrome, go to a page of interest, press F12 then the >> button and choose Audits

which that will bring up the Lighthouse home page.

Pressing “Perform an audit” will present you with options to include or exclude one of the five categories.

You invoke Lighthouse by selecting “Run audit”.  After an interval the report will be displayed. The Lighthouse report for google.co.uk is shown below.

The top bar gives information about the URL used and the emulation options used. Immediately underneath are the five categories with a score between 0 and 100, where 0 is the lowest possible score. This page explains the Lighthouse v3 Scoring Guide.

Selecting a category will take you to the relevant section of the report.

It is also possible to invoke Lighthouse using the Node command line tool. First install it using the Node Package Manager. I have used the -g option to install it as a global module.

npm install -g lighthouse

Once installed you can then use a command such as the following to run Lighthouse. The view option automatically opens Chrome and displays the HTML report.

lighthouse https://www.google.co.uk --view

If you prefer the output in JSON the following will create a file in the directory the command was run from

lighthouse https://www.google.co.uk --output=json --output-path=./google.json

Acknowledgements

Lighthouse home page

The Building Web Applications for the next Billion Users with Ire Aderinokun episode of Hanselminutes first made me aware of Lighthouse.