Readability First
Mobile screens are small and often viewed in bright sunlight. High legibility is the #1 goal. Avoid decorative scripts for body text.
System vs Custom Fonts
San Francisco (iOS) and Roboto (Android) are safe, highly legible choices. Custom fonts build brand but check for legibility at small sizes and loading performance.
Type Scale and Hierarchy
Use a limited scale (e.g., 12, 14, 16, 20, 24, 32). Clear size differences distinguish headers from body text, guiding the scanning eye.
Line Height and Length
Mobile needs generous leading (line-height). Aim for 140-150% of font size. Keep line length between 45-75 characters per line.
Minimum Sizes
Apple recommends 11pt minimum; Google recommends 12sp. For body text, 16px/sp is the modern standard for readability.
Dynamic Type
Support system font scaling. Users set large text for a reason. Using relative units (sp/rem) ensures your layout adapts without breaking.
Testing on Devices
Don't trust the desktop simulator. Test on an actual phone at arm's length. Check both high and low-density screens.