Distinguishing between phone and tablet browsers

Question

I know this question as been beaten to death, but I don't want anything super complicated here.

We have a companion app with our site that is only compatible with 7 and 10-inch tablets. We need to only alert users on those devices about our app. Problem is, I can't go by resolution. My Galaxy S3 has a 1280 x 720 screen, but is obviously not a tablet. I also can't for the life of me find out a way to get the physical size of the screen. The only solution I have come up with is detecting whether the device can make calls with MobileCapabilities.CanInitiateVoiceCall. Unfortuantely, by boss isn't happy with that solution.

So... How can I distinguish between a phone and a tablet in my web app (Server or client side)?

UPDATE: So far it seems that the best approach for Android is something from a blog post by the Android team: All Android phones use "Mobile" in the UserAgent string, so checking for "Mobile" *and "Android" will tell you if it's a phone, while just "Android" should be a tablet. iOS devices should be just as simple--checking for "iPhone" vs "iPad" seems to have worked so far.

Answer 1

I know this is a little late, but I was looking for the same thing.

Wurfl has wat you want. You can implement it easily and and even have an api you can query.

For ASP.NET application first you must place the one-off initialization.

public class Global : HttpApplication
{
   public const String WurflDataFilePath = "~/App_Data/wurfl.zip";
   private void Application_Start(Object sender, EventArgs e)
   {
       var wurflDataFile = HttpContext.Current.Server.MapPath(WurflDataFilePath);
       var configurer = new InMemoryConfigurer().MainFile(wurflDataFile);
       var manager = WURFLManagerBuilder.Build(configurer);
       HttpContext.Current.Cache[WurflManagerCacheKey] = manager;
   }
}  

And then use it like this.

var device = WURFLManagerBuilder.Instance.GetDeviceForRequest(userAgent);
var isTablet = device.GetCapability("is_tablet");
var isSmartphone = device.GetCapability("is_smartphone");

For more info check ASP.NET implementation

Hope this helps anyone else looking for this.