Many users of your page visit over a slow cellular network connection. Ensuring that your page loads fast over a simulated mobile network ensures that your page loads in a reasonable amount of time for your mobile users. Lighthouse flags any pages that don't load fast enough on mobile:
A fast page load on a mobile network is a baseline requirement for a site to be considered a Progressive Web App. See Baseline Progressive Web App Checklist.
How this audit fails
There are two main metrics regarding how users perceive load time:
- The page appears visually complete.
- The page is interactive. If a page appears visually complete at 1s, but the user can't interact with it until 10s, then the perceived page load time is 10s.
Lighthouse computes what time to interactive would be on a slow 4G network connection. If the time to interactive is more than 10s, the audit fails.
Each PWA audit is weighted equally in the Lighthouse PWA Score, except for three manual audits: Site works cross-browser, Page transitions don't feel like they block on the network, and Each page has a URL. Learn more in the Lighthouse Scoring Guide.
Record load performance shows you how to record a page load. Once you're familiar with the basics, do a page load recording and analyze the results to find JS work that can be deferred. See Rendering Performance for strategies.
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