Home / What Steeplejack checks
Website speed check
How quickly a homepage loads on a phone, what makes it heavy, which third-party trackers it carries and a rough estimate of its carbon per page view.
Speed results come from one Lighthouse run through Google’s PageSpeed Insights, so the score can move a little between surveys. Compare trends and look at the specific findings, rather than chasing a single number.
What the free survey checks
Lighthouse performance and lab Core Web Vitals
Slow loading and janky pages lose visitors and conversions; Google also uses field Core Web Vitals, from real Chrome visits, in search; lab figures only point to likely problems.
Compression and modern HTTP
Compressed HTML downloads several times faster; HTTP/2 and HTTP/3 load many files in parallel over one connection.
Page weight and request count
Heavy pages are slow on mobile data, cost visitors money and use more energy.
Images efficiently encoded and sized
Images are usually the heaviest part of a page. Modern formats and correct sizes cut weight without visible quality loss.
CSS and JavaScript compressed, minified and not oversized
CSS and JavaScript hold up the first paint and, for JavaScript, keep the phone busy after it downloads. Sending them smaller makes pages faster on mobile data and uses less energy.
Third-party tracker inventory
Each tracking and advertising script adds download weight and main-thread work, and may need consent under UK GDPR/PECR.
Carbon estimate per page view
Every byte a page sends uses energy in data centres, networks and visitors' devices. This is a rough estimate (Sustainable Web Design model) to compare pages and track progress, not a measurement.
No browser console errors or blocked scripts
Errors in the console usually mean something on the page isn’t working: a script that failed, or one the site’s own Content-Security-Policy blocked. Blocked scripts are often added by the host or CDN (analytics, toolbars, email obfuscation) without the site owner knowing.