What is Caller ID?

Image of a blank caller ID.
A caller ID device.

Getty Images / Ryan McVay

Caller ID is a feature that allows you to know who is calling you before answering the phone. Normally, the number of the caller is displayed on the phone. If you have a contact entry for the caller in your contact list, their name appears. But that's the name you have entered in your phone. You can see the name of the person as registered with his service provider, by subscribing to a flavor of the caller ID service called caller ID with name.

Caller ID is useful whenever you want to 'declare absent' in situations where you receive calls from people you don't want to answer. Many people find this useful when their boss calls. Others might choose to ignore calls from their ex-boyfriend/girlfriend or any hassling person.

Call Blocking

Often, Caller ID works with call blocking, another feature that blocks incoming calls from unsolicited parties or calls that come at inappropriate times. There are many ways of blocking calls. There is the basic way through your phone or smartphone, whereby you make a list of blacklisted numbers. Calls from them will automatically be rejected. You can choose to send them a message giving them any information you want, or simply make as if your device is off. 

Call blocking is one way of managing your calls and there are apps for smartphones that filter your calls in such a way that you can choose to deal with different calls in different ways. You can choose to square reject the call, to reject the call with a message, to forward the call to another phone, to transfer the call to voicemail or to take the call. 

Reverse Phone Lookup

Some people do not show their numbers, and upon receiving a call from them, you see 'private number'. There are apps that extract their phone numbers from their pool of millions (some even billions) of collected numbers and details.

Caller ID today has taken another direction, a reverse one. With a phone directory, you have a name and you want a corresponding number. There are now apps that bring you the name of the person behind a number. This is called reverse phone lookup. There are several apps for smartphones that offer this service, but once you use them, you give their your person number to include in their database. This means that other people will be able to look you up too. This may pose a privacy issue for some. But this is the way these apps work. Some even pry into your contact list once you install them on your device, and extract as many numbers with personal details as they can to feed their database.