Why Mobile Speed Scores Lag (and How to Close the Gap)
A practical action plan for eliminating the delta between your mobile and desktop Lighthouse scores with network shaping, routing, and UI trade-offs.
Throttle like Chrome does
Use Chrome's `Slow 4G / 4x CPU` profile or Lighthouse's simulated mobile to mimic harsh realities. Anything less optimistic is vanity testing.
Pair that with MakeWebsite.fast multi-location tests so you understand how packet loss in São Paulo or Jakarta affects the same build.
- Bake network shaping into CI, not just local debugging
- Benchmark CPU-bound components and refactor the slowest hooks
Streamline interaction density
Mobile layouts frequently ship the same React tree as desktop. Collapse carousels, lazy load tabs, and prefer server actions for chatty workflows.
Audit interaction cues. High-density UI leads to more input latency, which drags INP along with general speed perception.
Route traffic intelligently
Adopt regional hosting or edge rendering so mobile TTFB stays under 200ms globally. Static assets should never cross an ocean.
If you can't move origins yet, at least optimize DNS with Anycast and preconnect to every third-party that survives your performance budget review.
Key takeaways
- Simulated mobile tests must be part of CI to stay honest.
- Design density is a mobile performance lever, not just an aesthetic choice.
- Routing and DNS strategy can reclaim hundreds of milliseconds instantly.
FAQ
Should mobile score ever match desktop?
Matching is rare, but you should target <10 point delta. Anything larger signals CPU or routing debt.
Do PWAs fix mobile performance by default?
Service workers help repeat visits, but you still need lean bundles and disciplined rendering.
Related research
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