If the recipient of your call also has a computer, tablet, or smartphone and an Internet connection, there are several services that you can use to make free international calls. The most popular service as of 2015 is Skype, with over 600 million users worldwide. If you have a Mac with OS X 10.6.6 or above, then you can use FaceTime to call people with an iPhone, iPad or iPod Touch anywhere in the world for free.
Free Web calls are made using VoIP, or Voice over Internet Protocol. To make free Web calls, both you and the person you are calling need to be connected to the Internet. For you to make free calls, the person you are calling also needs to have the same app installed on his device. In most cases, the download is free, but you both need to create user names and log in to the service.
If you have a good broadband connection, then the quality of the free VoIP call can be excellent, but the quality diminishes if one of you has a poor connection.
If you wish to call a regular phone number from your computer rather than a computer or smartphone, then this is possible using a service such as Skype, ViberOut or LocalPhone -- but note that this is not free. Viber and WhatsApp are other services that enable free voice calls over the Internet.