Can this device make a phone call?

Can this device make a phone call? – Terence Eden’s Blog

I want to detect if a web browser is running on a device which is capable of placing a telephone call. Is that possible?

I'm going to go with a cautious "no - not quite". Although there are several proxies which get you part of the way there.

Here's a link to a telephone number "call me!" - the HTML is:

<a href="tel:+441234815259">call me!</a>

You can use tel: in just the same way you'd use http: or mailto:. It tells the User Agent to open the correct program to deal with a task - either a web-browser, email client, or - in this case - the telephone dialler.

But what happens if the user is on a desktop browser? Or using a tablet computer? Or on their smart TV? Usually an error message about how the device doesn't understand the link.

So, is there a way to use feature detection to only show a tel: to devices which can handle it?

User Agent Sniffing

This practice has been discredited for over a decade. UA Strings tend to lie. And, even when they don't lie, they're not very precise.

You could use this to discover if someone is running Android - but that doesn't tell you if it's a phone, tablet, TV, or VR headset.

NetworkInformation type

The navigator object contains network information. That should tell you if the device is on a 2G/3G/4G/5G connection.

Of course, your tablet also uses those connections. And your phone might be on WiFi.

Other properties

It is possible to detect if a device is multi-touch, has a battery, is a mobile device, can vibrate, etc.

All of which, taken together, might indicate that the device is a phone. But it is far from certain.

A Big Database Of Products

Companies like 51Degrees will sell you access to their database - which includes reporting whether a specific device supports phone calls. As will DeviceAtlas.

There used to be an Open Source database called WURFL - but ScientiaMobile closed down open access to it.

To be fair, 51Degrees have a generous free tier - but it is a little depressing that this sort of feature detection is locked in a proprietary product.

If you have any ideas how to solve this please give me a call!