Whether it's a video call or VoIP call, Skype is among the first names that spring to mind. Microsoft's software, however, is not the only one available
Well before it was purchased by Microsoft in 2011, Skype could count on a large fan base around the world. It's not hard to imagine why: with a single program, available for Windows, macOS, Linux, Android and iOS, it's possible to chat and make video calls for free.
Thanks to the integration with Microsoft services, the number of Skype users has skyrocketed to over 300 million unique monthly users (official data from Q1 2016). This does not mean, however, that the Microsoft software is the only one available when there is to make a video call or a VoIP call. Of altenatives to Skype for free there are dozens, each with its own features and functionality. In short, if Skype doesn't work or if Microsoft's VoIP platform doesn't suit you, you can easily opt for one of its "different twins".
Google Hangouts
Probably the most famous and widely used VoIP and video calling service after Skype, Google Hangouts offers its users all the major features also present in the Microsoft service. Available as a web platform, as an iOS and Android app and as a Chrome app, it integrates perfectly with other Big G web services and allows you to automatically import contacts from your Gmail address book or Android smartphone. Alternatively, you can send an invitation via email or phone number to take part in the VoIP call. In case of video calls, you can add up to 10 contacts at the same time: not many, but still enough for business meetings.
Viber
One of the most used messaging apps, Viber has over 800 million unique monthly users (slightly less than WhatsApp and Facebook Messenger and almost three times as many as Skype). It started out as a video calling app and soon established itself as one of the most viable alternatives to Skype for free: it allows you to send text messages (with stickers and emoji, of course), make VoIP calls and video calls (though not group calls), all without having to pay anything. Unless you want to subscribe to Viber Out, which allows you to make calls to landline and mobile numbers at low prices.
Available on both computers (Windows and macOS) and smartphones (you can download apps for Android and iOS), Viber also allows you to create group chats with up to 250 users with whom to share photos, audio and video.
For a messaging platform that can count on over 1 billion monthly active users, you don't need much of an introduction. Apart from sending messages and audio notes, WhatsApp can also be used to make calls and video calls. All you'll have to do is enter the conversation and press on the phone handset or camera icon: within seconds you'll be able to start talking freely with your friends. It's worth noting, however, that calls and video calls are only available through the app: WhatsApp Web, in fact, does not allow you to talk live with your friends.
Talky
Unlike the other free alternatives to Skype, Talky only works from a web browser. Apart from this (small) limitation, Talky seems to have been created specifically for business videoconferences: a maximum of 15 people can participate in each video call, while the administrator who creates the "room" can choose a URL of his choice to be shared later with other participants. Moreover, the access to the rooms can be password-protected, so as to ensure a higher level of security in case someone manages to guess the exact address of your video conference.
ooVoo
Available on Amazon Fire, Android smartphones and tablets, iPhone and iPad, Windows and macOS, ooVoo is a communication platform that makes group video calls its best weapon. Among the alternatives to Skype, in fact, ooVoo is the one that offers "more space": a single conference can contain up to 12 people simultaneously. Among other notable features we find the ability to watch YouTube videos with friends during a video call (even group), record messages to "deliver" via social networks and record video calls that you make, so you can review them whenever you want.
Facebook Messenger
Potentially it could be the most viable alternative to Skype (at least for number of users), but there are still few who can see it from this point of view. The fact is that Facebook Messenger makes available to users (not necessarily members of the social network, since the chat can also be used without a profile) tools and advanced features for chat, voice calls and video calls (both individual and group). All you have to do is enter one of the conversations (via app, Facebook or Messenger.com does not matter), enter one of the already active conversations (or create one from scratch) and start the call or video call. In the case of a group call, the messaging platform linked to Facebook will allow you to choose whether to let everyone participate or invite only some of the users.