Медиа запросы для популряных мобильных устройств в файлах CSS. Для корректного распознавания бразузерами требуется наличие тега meta viewport с содержимым "width = device-width"

iPhone 5, 5S, 5C and 5SE

/* Portrait and Landscape */
@media only screen 
  and (min-device-width: 320px) 
  and (max-device-width: 568px)
  and (-webkit-min-device-pixel-ratio: 2) {

}

/* Portrait */
@media only screen 
  and (min-device-width: 320px) 
  and (max-device-width: 568px)
  and (-webkit-min-device-pixel-ratio: 2)
  and (orientation: portrait) {
}

/* Landscape */
@media only screen 
  and (min-device-width: 320px) 
  and (max-device-width: 568px)
  and (-webkit-min-device-pixel-ratio: 2)
  and (orientation: landscape) {

}

iPhone 6, 6S, 7 and 8

/* Portrait and Landscape */
@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 667px) 
  and (-webkit-min-device-pixel-ratio: 2) { 

}

/* Portrait */
@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 667px) 
  and (-webkit-min-device-pixel-ratio: 2)
  and (orientation: portrait) { 

}

/* Landscape */
@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 667px) 
  and (-webkit-min-device-pixel-ratio: 2)
  and (orientation: landscape) { 

}

iPhone 6+, 7+ and 8+

/* Portrait and Landscape */
@media only screen 
  and (min-device-width: 414px) 
  and (max-device-width: 736px) 
  and (-webkit-min-device-pixel-ratio: 3) { 

}

/* Portrait */
@media only screen 
  and (min-device-width: 414px) 
  and (max-device-width: 736px) 
  and (-webkit-min-device-pixel-ratio: 3)
  and (orientation: portrait) { 

}

/* Landscape */
@media only screen 
  and (min-device-width: 414px) 
  and (max-device-width: 736px) 
  and (-webkit-min-device-pixel-ratio: 3)
  and (orientation: landscape) { 

}

iPhone X

/* Portrait and Landscape */
@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 812px) 
  and (-webkit-min-device-pixel-ratio: 3) { 

}

/* Portrait */
@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 812px) 
  and (-webkit-min-device-pixel-ratio: 3)
  and (orientation: portrait) { 

}

/* Landscape */
@media only screen 
  and (min-device-width: 375px) 
  and (max-device-width: 812px) 
  and (-webkit-min-device-pixel-ratio: 3)
  and (orientation: landscape) { 

}