How to detect Mobile & Retina Devices: 8 Techniques

In order to serve mobile-optimized content, you need to detect which visitors are coming from mobile devices and which aren’t.

Here we have list 8 method to detect mobile browsers so you can chose the best suitable to your needs, and give your user the best experience possible.

#1 PHP User Agent

We can test the user agent comparing with a list of known mobile user agents so you can redirect the user to a different version, add a new cookie, set a global variable to be used in your CMS, set a HTML class or anything else you may want to do.

The PHP code itself is quite simple.We'll use the preg_match() function to compare current browser with an array of mobile browsers:

<?php      
//Here is the known mobile user agents list      
$mobiles = array("iPhone","iPod");        
foreach( $mobiles as $mobile ) {          
if( preg_match( "#".$mobile."#i", $_SERVER['HTTP_USER_AGENT'] ) ) {              
//Ok, this is a mobile browser, let's redirect it!              
header('Location:http://mobile.mysite.com/');               
exit();         
}}  
?>

You can disable this test, via Cookie setting a link to yoursite?nomobile=1 then you can test this var before doing the redirection part:

<?php      
//let's check if we have a get or post or cookie set to nomobile      
if ( isset( $_REQUEST['nomobile'] ) && true == $_REQUEST['nomobile'] ) {          
//now we check if we have set the cookie, so we don't need the "get" in the URL all the time          
if ( ! isset($_COOKIE['nomobile']) ) {              
setcookie("nomobile", 1, (time()+60*60*24*30) );          
}
} else {          
//nevermind, let's check if current browser is a mobile            
//Here is the known mobile user agents list          
$mobiles = array("iPhone","iPod");            
foreach( $mobiles as $mobile ) {              
if( preg_match( "#".$mobile."#i", $_SERVER['HTTP_USER_AGENT'] ) ) {                  
//Ok, this is a mobile browser, let's redirect it!                  
header('Location:http://mobile.mysite.com/');                  
 exit();              
}          
}      
}  
?>

#2 JavaScript User Agent

The JS is more suitable for places where you have little or no control on the server side code, or you want to do something specific (like a landing page).

Moreover, the JS code is quite limited because you need to load the entire site before doing the redirection.

So, here is an example:

<script type="text/javascript">      
var mobiles = array["iPhone", "iPod"];//mobile devices      
var i;        for(i=0;i< mobiles.lenght;i++){         
 //testing if the RE matches the mobile agents          
var er = new RegExp(mobiles,"i");          
if( er.test( navigation.userAgent ) ) {              
window.location = "http://mobile.mysite.com/" ;          
}}  
</script>

#3 WordPress code

WordPress actually has an internal mobile sniffing tool so you’ll have a global variable to tell you if the current user is an iPhone or not (and a few other browsers).

Here is an example:

<?php      
function load_my_styles() {          
global $is_iphone; //loading global var here          
if( $is_iphone ) {              
wp_enqueue_style( 'iphone-style', get_stylesheet_directory_uri() . '/ iphone-style.css');          
} else {              
wp_enqueue_style('normal-style', get_stylesheet_directory_uri() . '/ style.css');         
 }  
 }     
 add_action( "wp_enqueue_scripts", "load_my_styles" );  
?>

#4 WordPress Plugins

Here are some options: 

#5 HTML Code for Retina

This is a simple way to be done in your

, while you’re calling your styles:

<link rel="stylesheet" type="text/css" src="css/common_style.css" />  
<link rel="stylesheet" type="text/css" src="css/retina.css" media="only screen and (-webkit-min-device-pixel-ratio:2)" />

#6 Media queries

The media queries allow you to conditionally apply styles.

/* Smartphones (portrait and landscape) ----------- */  
@media only screen   and (min-device-width : 320px)   
and (max-device-width : 480px) {  /* Styles */  }    /*
Smartphones (landscape) ----------- */  
@media only screen   and 
(min-width : 321px) {  /* Styles */  }   
 /* Smartphones (portrait) ----------- */ 
@media only screen   and (max-width : 320px)
 {  /* Styles */  }    
/* iPads (portrait and landscape) ----------- */  
@media only screen   and (min-device-width : 768px)  
 and (max-device-width : 1024px) {  /* Styles */  }   
 /* iPads (landscape) ----------- */  
@media only screen   and (min-device-width : 768px)   
and (max-device-width : 1024px)   and (orientation : landscape) {  /* Styles */  }    
/* iPads (portrait) ----------- */  
@media only screen   and (min-device-width : 768px)   
and (max-device-width : 1024px)   and (orientation : portrait) {  /* Styles */  }    
/* Desktops and laptops ----------- */  @media only screen   and (min-width : 1224px) {  /* Styles */  }   
 /* Large screens ----------- */  
@media only screen   and (min-width : 1824px) {  /* Styles */  } 
/* iPhone 4 ----------- */  @media  only screen and (-webkit-min-device-pixel-ratio : 1.5),  
only screen and (min-device-pixel-ratio : 1.5) {  /* Styles */  }

If you want to target only retina devices you can try:

@media only screen and (-webkit-min-device-pixel-ratio:2){  }

#7 Media Queries via JavaScript

An obscure technique perhaps...

You can test media queries using JavaScript, and if returns true, for example, you could conditionally change classes, change image src attributes, redirect your page.

<script type="text/javascript">      
//JS version for the retina query      
var modern_media_query = window.matchMedia( "screen and (-webkit-min-device-pixel-ratio:2)");        
if( modern_media_query.matches ){          
//DO ALL THE THINGS HERE      }  
</script>

#8 Htaccess code

The idea is similar to the first PHP method.

RewriteCond %{HTTP_USER_AGENT} “ipod|iphone|ipad|blackberry”[NC]  
RewriteCond %{REQUEST_URI} ^/$  
RewriteRule ^ http://m.yoursite.com%{REQUEST_URI} [R,L]

Janeth Kent

Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN AND DEVELOPMENT.