Skype (pronunciation: skaɪp) is a VoIP program from Microsoft, with which you can make calls over the internet.

The program is available for free for Windows (Windows 2000 and newer), macOS (Mac OS X 10.3 or higher), Linux, iOS, Android and Windows Phone. Skype claims to be free of spyware and is written by the authors of Kazaa: Niklas Zennström and Janus Friis.


The conversations take place via a Skype proprietary protocol with peer-to-peer technology. This protocol is designed in such a way that it is generally not hampered by firewalls. Conversations over Skype deal with 256 bit AES - encryption encrypted over the Internet. Eavesdropping (internet tap) is virtually impossible. However, there is talk of spying on citizens by the government. Alternative protocols are the open SIP and H.323.

In September 2005, Skype Global was acquired by eBay, which Skype later largely sold on to the Silver Lake investment company. In May 2011, Microsoft signed a takeover agreement for approximately USD 8.5 billion. Skype as a product remains, but may be integrated into Xbox Live, Kinect and

Acquisition of Windows Live Messenger

In 2013, Skype had replaced Microsoft's chat program, Windows Live Messenger. Between April 8, 2013 and April 30, 2013, Microsoft forced all existing Messengers users to move to Skype. The Messenger service went offline after 30 April. The move was in stages starting with the English accounts and ending with the Portuguese accounts.

After the upgrade, users could no longer log in, but were welcomed at Skype with a notification. Accepting the notification will install Skype and remove Messenger automatically. The transition was the first major move that Microsoft made with Skype since the takeover in 2011. The takeover was a step in the direction of competitors such as WhatsApp, and Google Talk. The availability of Skype on many platforms makes the platform more attractive than Messenger in the long term.


  • SkypeIn: Allows friends without Skype cell phone or landline to be reached on Skype. This function is only available in 24 countries including the Netherlands. Belgium has too strict a policy for this (BIPT) and does not allow this.
  • SkypeOut: Call from Skype on a PC to a person's mobile or landline. This is done with a prepaid credit or a subscription, per country or with a "Europe package" or "world package".
  • Skype To Go in 18 countries: Skype as an intermediate person, who is not sitting at his PC and want to call someone abroad. This also happens with a prepaid credit or a subscription. Skype calls the contact to whom Skype has been notified of the fixed or mobile number in advance, after which Skype has provided a "skype to go" number for that person.
  • Skype Mobile only in the United Kingdom and in Ireland with certain types of mobile devices: the skype program on the mobile phone.
  • Sending text messages, files, contact addresses as with all IMs within the Skype program for free, to be paid outside. Voicemail use is always against payment.
  • Webcam support (video chat, video telephony), audio calls remain possible
  • Skype also works on a PlayStation Portable (PSP) and on a PlayStation Vita (PSVita) by downloading an app from PlayStation Store.

In the news

  • September 14, 2005: Skype was purchased by eBay for 1.9 billion Euros in shares and in cash.
  • On 21 February 2006, Postbank was the first Dutch bank to offer customers the opportunity to contact customer service directly via Skype.
  • May 15, 2006: US users can use SkypeOut free of charge for calls within and between the US and Canada until the end of 2006.
  • January 3, 2007: from January 18, Skype will charge a starting rate for SkypeOut for calls.
  • April 2009: Skype was downloaded more than 4 million times within 6 weeks. Few applications achieve that within such a time frame.
  • December 2010: Skype users can share their profiles via measurement type.
  • May 2011: Microsoft takes over Skype.
  • April 2013: Windows Live Messenger to Skype migration.
  • July 2013: documents show that Skype has provided the US secret service, the NSA, with access to its servers.
  • August 2019: Microsoft would listen to users via the Skype translation function.


  • On June 23, 2011, Skype had 22,409,728 users simultaneously online.
  • At the end of 2007, Skype had more than 276 million registered users.


  • A disadvantage of Skype is that a connection to other VoIP services is not possible, since Skype works with a closed protocol and both parties must therefore use Skype. It is not possible to use Skype for conversations with services based on the SIP protocol such as Free World Dialup, Parlino, VoIPBuster or ActionVoIP.
  • Many mobile phone providers do not allow VoIP to be used via the mobile phone. The aforementioned "Skype-to-go" is a remedy, at least for foreign calls, but in 2011 it only works in 18 countries. The Benelux is not in that country group (see the drop-down menu of the footnote).
  • One can only call emergency numbers via Skype under strict conditions.


  • Skype works on the TCP stack of the operating system. It sometimes fills this stack completely, so that other programs that want to use this stack no longer function. It is sometimes difficult for many system administrators to discover that Skype is the cause, because there is usually still enough memory and little CPU load.
  • The purpose of Skype is to be able to make telephone calls between computer systems. Straight through firewalls and underlying (secured) network infrastructures. This is also the risk with regard to security. For example, hackers could use the "voice stream" which consists of data to pass through security in networks.
  • A computer on which Skype is installed can act as a relay (supernode), leaving less bandwidth for other activities such as downloading.
  • There is no longer any control mechanism on Skype traffic. Computers become slower, uncontrolled use of bandwidth and uncontrollable links to other (non-proprietary systems) by an "external party" by means of a proprietary protocol can be undesirable and unsafe.
  • Another point is that the Skype user agreement (End-User License Agreement (EULA)) no longer mentions supernodes. However, the "Skype Guide for Network Administrators" mentions the existence of supernodes.
  • The use of a properly configured firewall makes it possible to prevent the use of a Skype station as a supernode.

"Skype" is at the 18th Position in this list.

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