Practice : Mobile-First Design

Purpose and Strategic Importance

Mobile-First Design is a design strategy that prioritises the mobile user experience before scaling up to tablet and desktop interfaces. With mobile usage often exceeding desktop, designing for smaller screens first ensures the core user experience is focused, efficient, and accessible - rather than an afterthought.

This approach leads to better performance, clearer user journeys, and design constraints that encourage simplicity, prioritisation, and greater usability for all users, regardless of device.

Description of the Practice

  • Start designing interfaces for mobile screens, then progressively enhance for larger viewports.
  • Focus on key user tasks, prioritised content, and simple interactions that translate across devices.
  • Use responsive design techniques such as flexible layouts, media queries, and scalable assets.
  • Emphasise performance and accessibility from the outset.
  • Validate assumptions through mobile usability testing and analytics.

How to Practise It (Playbook)

1. Getting Started

  • Begin with mobile wireframes before desktop layouts.
  • Limit UI elements to only the most critical actions or content on small screens.
  • Use design systems that support responsive components and scalable typography.
  • Test prototypes on real mobile devices - not just emulators.

2. Scaling and Maturing

  • Apply progressive enhancement to introduce complexity as screen size increases.
  • Optimise performance by reducing mobile payload size (e.g. lazy loading, asset compression).
  • Use feature flags or adaptive rendering to tailor functionality by device.
  • Build automated tests to verify layout and interaction across breakpoints.
  • Incorporate analytics and heatmaps to understand real mobile usage patterns.

3. Team Behaviours to Encourage

  • Put mobile users at the centre of UX discussions and backlog prioritisation.
  • Collaborate closely across design, development, and QA to ensure responsive fidelity.
  • Share insights from mobile testing to inform roadmap and design decisions.
  • Treat performance, accessibility, and responsiveness as non-negotiable quality metrics.

4. Watch Out For…

  • Designing for desktop first and retrofitting to mobile, causing awkward UX.
  • Assuming all users have the same capabilities or connectivity on mobile.
  • Overloading mobile screens with complex workflows or dense content.
  • Ignoring mobile analytics or accessibility testing.

5. Signals of Success

  • Mobile experience is fast, focused, and easy to use.
  • Core functionality is accessible across devices and screen sizes.
  • Bounce rates drop and conversions improve for mobile users.
  • Development velocity improves due to reusable responsive design patterns.
  • Mobile UX is seen as a first-class citizen - not a constraint.