# Mobile PageSpeed from 35 to 92: +20% conversion rate (before/after)

- Outcome: Won
- Page type: Site-wide (Ecommerce)
- Elements: Themes, page builders & page speed
- Test run by: [Vasta](https://liftarchive.com/practitioners/vasta/)
- Commentary by: LiftArchive (our analysis, not theirs)
- Original source: https://vasta.me/speed-articles/from-35-to-92-pagespeed-growth
- Page: https://liftarchive.com/test/anti-aging-supplement-pagespeed/

After a speed overhaul took mobile Lighthouse scores from 35 to 92 on the homepage and from 30 to 91 on product pages, conversion rate rose 20%. Vasta did the work for an anti-aging supplement brand. This was a before-and-after comparison, not a split test.

## Result

**+20% conversion rate (before/after)**

- Conversion rate: +20% after the speed work.
- Total sales: +13%.
- The agency put the return at 21 times the cost of the work.
- These come from comparing periods before and after, so other changes over time may be part of the gain.

## Control

Slow homepage and product pages on mobile. Hero images appeared after 4 to 5 seconds on 4G, third-party scripts tied up the phone's processor, and the layout shifted while loading.

## Variant

The same pages after speed work, scoring 92 on the homepage and 91 on product pages in mobile Lighthouse.

## Why it likely won (our reading)

- Visitors were likely leaving before the page had even shown the offer.
- Cutting heavy third-party scripts makes mid-range phones respond faster.
- Less layout shift means fewer mis-taps and less frustration.

## Caveats

Before/after comparison, not a split test, so seasonality, ads or other changes could explain part of the lift. Time periods and traffic were not shared.

## How to run this test

- Hypothesis: If we cut load time and layout shift on mobile, then conversion rate will rise because more visitors see the offer before giving up.
- Primary metric: Mobile conversion rate
- Guardrail: Bounce rate
- Guardrail: Core Web Vitals scores
- Guardrail: Revenue from removed apps or scripts
- Who should test it: Stores with low mobile speed scores and lots of third-party apps. If your site already loads fast, gains will be much smaller. Speed is hard to split test, so a holdout or staged rollout gives cleaner proof than before/after.

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Credit: Vasta ran this test and owns the result. Summary and commentary by LiftArchive (https://liftarchive.com/test/anti-aging-supplement-pagespeed/).
Usage: Free to use, quote and build on, with credit and a link: name the practitioner or organization that ran the test and link to its LiftArchive page. The results belong to the practitioners who ran and shared them; the summaries and commentary are LiftArchive's.