What to do
This section focuses on usability hygiene , or the basics that need to addressed to optimise conversion , and avoid interrupting or forcing users to think about things that should be simple .
You need to work hard to meet the expectations of users who are becoming more accustomed to high quality apps , published by brands that invest time and effort creating , testing and optimising services , to deliver usable , robust , and sometimes delightful user experiences .
Text and content is easy to read ( even outside in sunlight )
For text to always be legible you should use a font size at-or-above 11 points ( even when users select a small text size ); and the font used throughout the app should be consistent . Make sure there is sufficient perceivable contrast between the app content and the background , especially when used outside in sunlight . In Android , type should be specified in scale-independent pixels ( sp ), and layouts supporting scalable types tested against these settings .
“ 34 % prefer an app - versus a mobile website - when they have poor WiFi or 3G connection .”
Google App Re-engagement , UK , 2015
Content is accessible when user has no connection ( i . e . no 3G or WiFi )
Make sure that key content within the customer journey is accessible - i . e . cached in-app - even when there is little or no data connection via either 3G or WiFi . This needs to be carefully identified and prioritised , to enable a seamless user experience and to avoid abandonment .
Spacing and size of content and controls make them easy to interact with
Make it easy for users to interact with app content and controls by providing sufficient spacing between all elements for controls to be easily touched / tappable . Design touch / tap elements that provide direct feedback when normal , pressed , disabled , etc . ( e . g . Android uses illumination and dimming ) to help the user see the whole tappable area and learn what the tappable elements are throughout the app . Android recommends controls have a touch target size of 48dp for on screen elements such as buttons , icons , tabs with icons , etc .
iOS recommends tappable controls have a hit target of about 44 x 44 points .
Modal views are used for self-contained tasks within a multi-step process
When users need to achieve a simple selfcontained task within a multistep process , and that task doesn ’ t belong in the app UI constantly , use a modal view . iOS has two modal views : vertical and flip . They can either cover the whole or part of the screen , contain copy and functionality , and should be completed or cancelled , and exited easily
Primary call-to-action buttons are sticky / persistently visible ( even when screen is scrolled )
It is good practice to have call-to-action buttons above the fold , and on pages with rich or detailed content , it can be enabled by having a persistently sticky button at the bottom of the screen - visible even when the screen is scrolled - for users to act at any given moment . ( See images 37 , 38 , 39 )
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