MacBook Air and iPad

Flipboard app on iPad
Widescreen (Retina): 2560x1600 (compatible with any smaller widescreen)
Samsung Galaxy Tab & iPad: 2048x2048 (compatible with almost all tablets)
HTC, Samsung Galaxy & iPhone: 1080x1920 (compatible with almost all new smartphones)
MacBook Air
Widescreen (Retina): 2560x1600 (compatible with any smaller widescreen)
Samsung Galaxy Tab & iPad: 2048x2048 (compatible with almost all tablets)
HTC, Samsung Galaxy & iPhone: 1080x1920 (compatible with almost all new smartphones)
Ultrabook MacBook Air
Widescreen (Retina): 2560x1600 (compatible with any smaller widescreen)
High Definition HD 1080p: 1920x1080 (compatible with any smaller HD screen)
Samsung Galaxy Tab & iPad: 2048x2048 (compatible with almost all tablets)
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