Mobile traffic now exceeds desktop for most websites, yet mobile conversion rates are typically 50% lower. This guide covers mobile-specific A/B testing strategies to close that gap.
The Mobile Conversion Gap
60%+
of traffic is mobile
50%
lower mobile CVR
$$$
massive opportunity
The gap exists because most sites are designed desktop-first and "adapted" to mobile. Mobile-specific testing can unlock significant conversion improvements.
High-Impact Mobile Tests
1 Touch target size
High ImpactButtons should be at least 44×44px for easy tapping
2 Sticky CTA
High ImpactFixed bottom button vs. inline CTA placement
3 Form field types
Medium ImpactEmail keyboard, numeric pad for phone numbers
4 Thumb-zone optimization
High ImpactPlace key actions in easy-to-reach areas
5 Click-to-call
High ImpactProminent phone button for local businesses
The Thumb Zone: Where to Place CTAs
Most users hold their phone with one hand and use their thumb to navigate. The "thumb zone" is the area easily reachable:
Easy
Bottom center of screen
Okay
Middle of screen
Hard
Top corners
Test idea: Move your primary CTA to a sticky bottom bar. This keeps it in the easy thumb zone regardless of scroll position.
Mobile Form Optimization
Forms are where mobile conversions die. Test these optimizations:
type="email" shows @ key, type="tel" shows number pad
Minimum 48px height for easy tapping
Never use side-by-side fields on mobile
Proper autocomplete attributes for one-tap filling
Apple Pay, Google Pay can lift mobile conversion 10-20%
Always Segment by Device
A test that wins overall might be losing on mobile (or vice versa). Always check device segments:
Example: Headline Test Results
In this example, rolling out the "winner" would hurt your mobile users. Always check segments before shipping.
Mobile App A/B Testing
App testing has unique considerations:
Challenges
- • App store review delays
- • Users on old versions
- • Harder to iterate quickly
- • Need mobile SDK integration
Solutions
- • Remote config for instant changes
- • Feature flags for gradual rollout
- • Server-driven UI components
- • Force update for critical tests
Close the Mobile Gap
Mobile optimization isn't about making your desktop site "work" on phones—it's about designing for mobile-first behaviors. Thumb zones, form optimization, and sticky CTAs are your starting points.
Always segment your test results by device. A winning test on desktop might be losing on mobile, and with 60%+ of traffic coming from phones, you can't afford to ignore that.