Lighthouse
What is Lighthouse?
Lighthouse is an open-source, automated tool for improving the quality of web pages.
Click here to read more about lighthouse on the Google Developer website: https://developers.google.com/web/tools/lighthouse
Lighthouse simulates the page being tested on a mobile device and gives a score in several categories. It is a quick way to check that the site is performing well and meets all current best practices.
Typical Results
Below is a summary of the results for one of our websites:
What do the results mean?
In short, green means the site is performing well.
Lighthouse is not just testing how quickly a site loads. It is testing how responsive the site feels to your users. For example, your users may get a good experience if your site shows a page layout quickly, even if not all the content is shown immediately. They will feel a site is responsive if they can interact with it (scroll, press buttons, etc). It is important to design the site so that the initial page is loaded quickly and the site becomes interactive.
Note that many sites claim to be responsive and/or mobile-freindly but they are referring to something else. They mean that the layout of the site changes for small screens. They are not saying anything about how the site performs on low-end mobile devices or over mobile networks.
My site already loads in less than 2 seconds, doesn't it?
When you check your own website you are not getting the experience a first time user receives. When a user first visits your site they will not see the page until all the images and scripts have been downloaded and processed. In future visits these may already be available and the site will appear to load quickly. You need to check your site as a new user to get the real story.
Also, you are probably checking your site on a fast broadband connection, on a recent high end mobile device or laptop. Real users are probably viewing the site over a 3G or 4G mobile connection and not everyone has the latest iPhone. Older or cheaper devices will show the site much more slowly, if at all.
The devices we use for testing are real devices with low memory and a slow cpu. It is common for websites to take 30 seconds or more to load on these devices. Worse, if a website exceeds the memory available on a mobile device it will simply be closed without warning.
The results above are for a real website created by appZuka tested on a low end device over a mobile connection. Check your own website and you'll understand how impressive these scores are.
How can I test my own website?
You can test your site on a laptop or desktop computer running the Chrome browser. Follow the link above for guidance. If you are not familiar with the Chrome developer tools get in contact and we will run a Lighthouse audit on your site and send you the results.
Related Tech Notes
WebPageTest
Diagnosing and fixing performance issues
Lighthouse Auditing
Measuring Website Performance