Skype

This article is about the VoIP software. For the company, see Skype Technologies.

Skype

Screenshot Skype 6.3 running on Windows 7
Developer(s)	Skype Technologies Microsoft
Initial release	August 2003 (2003-08)
Stable release	Windows, UWP 15.119.201.0 / 6 May 2024 (2024-05-06) Windows, desktop 8.119.0.201 / 6 May 2024 (2024-05-06) macOS 8.119.0.201 / 6 May 2024 (2024-05-06) Linux 8.119.0.201 / 6 May 2024 (2024-05-06) Android 8.119.0.202 / 6 May 2024 (2024-05-06) iOS 8.119.0.201 / 6 May 2024 (2024-05-06) (iPhone and iPad)
Written in	Embarcadero Delphi, Objective-C (iOS, OS X), C++ with Qt4 (Linux)
Operating system	Microsoft Windows, Windows Phone, Xbox One, OS X, iOS, Symbian, Linux, Android, BlackBerry OS, PSP, PSVita, WebOS and PS4
Available in	Multilingual
Type	Voice over IP, instant messaging, videoconferencing
License	Proprietary, some paid features
Website	www.skype.com

Skype /ˈskaɪp/ is a proprietary voice-over-IP service and software application.

Skype was first released in August 2003 written by Estonian developers Ahti Heinla, Priit Kasesalu, and Jaan Tallinn, Danish Janus Friis, and Swedish Niklas Zennström, who had also originally developed Kazaa. Skype has 663 million registered users as of the end of 2010. It was bought by Microsoft in 2011 for $8.5 billion. Microsoft's Skype division headquarters is in Luxembourg, but most of the development team and 44% of the overall employees of the division are still situated in Tallinn and Tartu, Estonia.

The service allows users to communicate with peers by voice using a microphone, video by using a webcam, and instant messaging over the Internet. Phone calls may be placed to recipients on the traditional telephone networks. Calls to other users within the Skype service are free of charge, while calls to landline telephones and mobile phones are charged via a debit-based user account system. Skype has also become popular for its additional features, including file transfer, and videoconferencing. Competitors include SIP and H.323-based services, such as Linphone and Google Voice.

Unlike most other VoIP services, Skype is a hybrid peer-to-peer and client–server system. It makes use of background processing on computers running Skype software, and this is reflected in Skype's original proposed name of Sky Peer-to-Peer.

Some network administrators have banned Skype on corporate, government, home and education networks, citing reasons such as inappropriate usage of resources, excessive bandwidth usage, and security concerns.

In November of 2010 Skype began volunteer participation in a U.S. Government spy program titled PRISM by allowing the NSA unfettered access to its data center supernodes. It was not until February 2011 that the company was served with a directive to comply signed by the attorney general. Skype continues to allow the NSA access to its data streams to this day.

History

Main article: Skype Technologies § History

Skype was founded in 2003 by Janus Friis from Denmark and Niklas Zennström from Sweden. The Skype software was developed by the Estonians Ahti Heinla, Priit Kasesalu, and Jaan Tallinn, who together with Friis and Zennström were also behind the peer-to-peer file sharing software Kazaa. In August 2003, the first public beta version was released.

eBay acquisition

On 12 September 2005, eBay Inc. agreed to acquire Luxembourg-based Skype Technologies SA for approximately US$2.5 billion in up-front cash and eBay stock, plus potential performance-based consideration.

Silver Lake, Andreessen Horowitz and the Canada Pension Plan Investment Board acquisition

On 1 September 2009, it was announced that eBay was selling 65% of Skype for US$1.9 billion, valuing Skype at US$2.75 billion.

Microsoft acquisition

On 10 May 2011, Microsoft Corporation acquired Skype Communications, S.à r.l for US$8.5 billion. The company was incorporated as a division of Microsoft, and Microsoft acquired all of the company's technologies with the purchase. This was completed on 13 October 2011.

Windows Live Messenger merger

Microsoft phased out its long-standing Windows Live Messenger instant messaging service in favour of Skype, although Messenger will continue in mainland China. Microsoft began this transition in April 8, 2013, and completed the move by April 30.

Features

Main article: Features of Skype

Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype directory. Skype allows these registered users to communicate through both instant messaging and voice chat. Voice chat allows telephone calls between pairs of users and conference calling, and uses a proprietary audio codec. Skype's text chat client allows group chats, emoticons, storing chat history and editing of previous messages. Offline messages were implemented in a beta of version 5, but removed after a few weeks without notification. The usual features familiar to instant messaging users — user profiles, online status indicators, and so on — are also included.

The Online Number, a.k.a. SkypeIn, service allows Skype users to receive calls on their computers dialed by conventional phone subscribers to a local Skype phone number; local numbers are available for Australia, Belgium, Brazil, Chile, Colombia, Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, Ireland, Japan, Mexico, Nepal, New Zealand, Poland, Romania, South Africa, South Korea, Sweden, Switzerland, Turkey, the Netherlands, the United Kingdom, and the United States. A Skype user can have local numbers in any of these countries, with calls to the number charged at the same rate as calls to fixed lines in the country. The countries on this growing list are referred to collectively as the SkypeIn Countries.

Skype supports conference calls up to 25 people at a time. Skype also supports video chat between two people for free. Screen sharing and group video calling is available for Premium subscribers between a maximum of 10 people.

Skype does not provide the ability to call emergency numbers such as 112 in Europe, 911 in North America, 000 in Australia, 100 Call Police in India and Nepal The U.S. Federal Communications Commission (FCC) has ruled that, for the purposes of section 255 of the Telecommunications Act, Skype is not an "interconnected VoIP provider". As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.

In 2011 Skype partnered with Comcast to bring its video chat service to Comcast subscribers via their HDTV sets.

On June 17, 2013 Skype released a free video messaging service which can be operated on Windows and Mac OS, iOS, Android and BlackBerry.

Usage and traffic

Usage and traffic

Date Total user accounts (millions) Active users, daily use (millions) Skype to Skype minutes (billions) SkypeOut minutes (billions) Revenue USD (millions) Q4 2005 74.7 10.8 — — — Q1 2006 94.6 15.2 6.9 0.7 35 Q2 2006 113.1 16.6 7.1 0.8 44 Q3 2006 135.9 18.7 6.6 1.1 50 Q4 2006 171.2 21.2 7.6 1.5 66 Q1 2007 195.5 23.2 7.7 1.3 79 Q2 2007 219.6 23.9 7.1 1.3 90 Q3 2007 245.7 24.2 6.1 1.4 98 Q4 2007 276.3 27.0 11.9 1.6 115 Q1 2008 309.3 31.3 14.2 1.7 126 Q2 2008 338.2 32.0 14.8 1.9 136 Q3 2008 370 33.7 16.0 2.2 143 Q4 2008 405 36.5 20.5 2.6 145 Q1 2009 443 42.2 23.6 2.9 153 Q2 2009 483 ? 25.5 3.0 170 Q3 2009 521 ? 27.7 3.1 185 Q4 2009 560 ? 36.1 ? ? Q1 2010 ? ? 190 12.8 860 Q2 2010 ? ? ? ? ? Q3 2010 ? ? ? ? ? Q4 2010 ? ? ? ? ? Q1 2011 ? ? ? ? ? Q2 2011 ? ? ? ? ? Q3 2011 663 ? ? ? ? Q4 2011 ? ? ? ? ? Q1 2012 ? ? ? ? ? Q2 2012 ? ? ? ? ? Users may have more than one account; it is not possible to count users, only accounts. The volume of international traffic routed via Skype is significant. It has become the largest international voice carrier (by minutes of calls).

Year	International call market share
2005	2.9 %
2006	4.4 %
2008	8 %
2009	12 %
2010	13 %
2012	34 %

In January 2011, after the release of video calling on the Skype client for iPhone, Skype reached a record 27 million simultaneous online users. This record was broken with 29 million simultaneous online users on 21 February 2011, and again on 28 March 2011 with 30 million online users. On 25 February 2012, Skype announced that it has over 32 million users for the first time ever. As of 5 March 2012, it has broken to 36 million simultaneous online users and less than a year later, on 21 January 2013, Skype had more than 50 million concurrent users online. In June 2012, Skype had surpassed 70 million downloads on an Android Device.

On 19 July 2012, Microsoft announced that Skype users had logged 115 billion minutes of calls over the quarter, up 50% since the last quarter.

System and Software

Client applications and devices

Skype runs on a number of platforms including Microsoft Windows (XP, Vista, 7, 8), OS X (10.6 or newer), Linux (Ubuntu and others), Android, BlackBerry 10, iOS, Symbian and Windows Phone.

On 29 October 2007, Skype launched its own mobile phone under the brand name 3 Skypephone, which runs a BREW OS.

Skype also offers a Skype Wi-Fi Phone, which is a wireless mobile phone that allows users to make Skype calls, using a wireless Internet connection. The Skype Wi-Fi Phone has an on-screen menu that lets Skype users see who is online and available to talk, similar to what is seen on a PC. It can also be used to talk with non-Skype users. SkypeOut minutes can be used to call any phone for a low price and no monthly fee. The Skype Wi-Fi phone does not contain a web browser and so can not access hotspots that require web-based login or authentication.

Other platforms officially supported include:

• The Nokia N800, N810 and N900 Internet Tablets, which run Maemo
• The Nokia N9, which runs MeeGo, comes with Skype voice calling and text messaging integrated however lacks video-calling.
• Both the Sony mylo COM-1 and COM-2 models
• The PlayStation Portable Slim and Lite series, though the user needs to purchase a specially designed microphone peripheral. The PSP-3000 has a built in microphone, which allows communication without the Skype peripheral. The PSP Go has the ability to use Bluetooth connections with the Skype application, in addition to its built-in microphone. Skype for PlayStation Vita may be downloaded via the PlayStation Network in the U.S. It includes the capability to receive incoming calls with the application running in the background.
• Samsung Smart TV has a Skype app which can be downloaded for free. It uses the built in camera and microphone for the newer models. Alternatively a separate mountable Skype camera with built in speakers and microphones is available to purchase for older models.
• Some devices are made to work with Skype by talking to a desktop Skype client or by embedding Skype software into the device. These are usually either tethered to a PC, or have a built-in Wi-Fi client to allow calling from Wi-Fi hotspots like the Netgear SPH101 Skype Wi-Fi Phone, the SMC WSKP100 Skype Wi-Fi Phone, the Belkin F1PP000GN-SK Wi-Fi Skype Phone, the Panasonic KX-WP1050 Wi-Fi Phone for Skype Executive Travel Set, the IPEVO So-20 Wi-Fi Phone for Skype and the Linksys CIT200 Wi-Fi Phone.

Third-party developers, such as Truphone, Nimbuzz and Fring, previously allowed Skype to run in parallel with several other competing VoIP/IM networks (Truphone and Nimbuzz provide TruphoneOut and NimbuzzOut as a competing paid service) in any Symbian or Java environment. Nimbuzz made Skype available to BlackBerry users and Fring provided mobile video calling over Skype as well as support for the Android platform. Skype disabled Fring users from accessing Skype in July 2010. Nimbuzz discontinued support on request of Skype in October 2010.

Before and during the Microsoft acquisition, Skype withdrew licensing from several third parties producing software and hardware compatible with Skype. The Skype for Asterisk product from Digium was withdrawn as "no longer available for sale". The Senao SN358+ long-range (10–15 km) cordless phone were discontinued due to loss of licenses to participate in the Skype network as peers. In combination these two products made it possible to create roaming cordless mesh networks with robust handoff.

Protocol

Main article: Skype protocol

Skype uses a proprietary Internet telephony (VoIP) network called the Skype protocol. The protocol has not been made publicly available by Skype and official applications using the protocol are closed-source. Part of the Skype technology relies on the Global Index P2P protocol belonging to the Joltid Ltd. corporation. The main difference between Skype and standard VoIP clients is that Skype operates on a peer-to-peer model (originally based on the Kazaa software), rather than the more usual client–server model (note that the very popular SIP model of VoIP is also peer-to-peer, but implementation generally requires registration with a server, as does Skype).

As far as networking stack support is concerned, Skype currently only supports the IPv4 protocol. It lacks support for the next generation Internet protocol, IPv6.

Protocol detection and control

Many networking and security companies claim to detect and control Skype's protocol for enterprise and carrier applications. While the specific detection methods used by these companies are often private, Pearson's chi-squared test and Naive Bayes classification are two approaches that were published in 2008. Combining statistical measurements of payload properties (such as byte frequencies and initial byte sequences) as well as flow properties (like packet sizes and packet directions) has also shown to be an effective method for identifying Skype's TCP- and UDP-based protocols.

Audio codecs

G.729 and SVOPC. Skype added a Skype-created codec called SILK to Skype 4.0 for Windows and other Skype clients. SILK is intended to be "lightweight and embeddable".

Video codecs

VP7 is used for versions prior to Skype 5.5

As of version 5.7 VP8 is used for both group and one on one standard definition video chat and H.264 is used for 720p and 1080p high definition group and one on one video chat.

Release history

Windows

Windows Version History

Color Meaning Red Release no longer supported Green Release still supported Blue Future release Version Release Date Features/description 3.6.0.244 15 December 2007 ? 3.6.0.216 7 December 2008 ? 4.0.0.206 13 February 2009 ? 4.0.0.215 13 March 2009 ? 4.0.0.216 20 March 2009 ? 4.0.0.224 3 April 2009 ? 4.0.0.226 22 April 2009 ? 4.0.0.227 3 June 2009 ? 4.1.0.136 30 June 2009 ? 4.1.0.141 25 July 2009 ? 4.1.0.166 3 September 2009 ? 4.1.0.179 12 October 2009 ? 4.2.0.152 25 February 2010 ? 4.2.0.155 10 March 2010 ? 4.2.0.158 8 April 2010 ? 4.2.0.163 27 April 2010 Hotfix 4.2.0.166 10 May 2010 Hotfix 4.2.0.169 20 May 2010 Skype crashed with some web-cameras when video calling, for example with Microsoft Lifecam Show and HP Elite Autofocus web-cam. 4.2.0.187 6 September 2010 Fixes issues 5.0.0.152 14 October 2010 Group video calling (beta) Skype Home Integration with Facebook Offline instant messaging New contact search and improved contact adding Enhanced call quality experience User interface refresh 5.0.0.156 14 December 2010 Call Phones Skype crashed on Call Phones area when user had more than one recently expired subscriptions Contact requests sent from Skype for Windows in Cyrillic letters were shown as "?" marks on incoming contact request view on Skype for Android Skype crashed on login for users who had two or more dots ("..") in their username in row. Full screen sharing selection was not updated when selecting second monitor for screen sharing Fixed the issues with Freetalk Everyman webcam and FaceVsion Touchcam N1 not going into HD video calling mode. Note! Camera firmware needs to be upgraded as well, see instructions for Freetalk and FaceVsion. 5.1.0.104 6 January 2011 Video calls now start by default in 640x480 resolution Video calls on powerful computers start in 30 frames per second Improved surfacing of 'Add Contact' and 'Create a Group' functions Group video calling out of Beta 5.1.0.112 31 January 2011 Hotfix 5.2.0.113 15 March 2011 Modified call phones dialog with integrated contact number search New presence-aware call button, including a drop-down of associated contact numbers Modified presence icons, to better indicate a contact's availability status Improved call handling when you run out of credit New simple button to share files and contacts Improvements to help you find active calls New look for the contact profile area 5.3.0.108 7 April 2011 Improved quality of video received from Skype on mobile devices Skype shows users' presence icons on collapsed contact profile cards Conversation topic editing button is now always available on the conversation header If a phone number is added to a profile after a failed call attempt, Skype starts a call automatically Automatically switch to SMS entry after user adds mobile phone number to profile after failing to send SMS due to lack of phone number 5.3.0.111 20 April 2011 Hotfix 5.3.0.113 24 May 2011 Hotfix 5.3.0.116 26 May 2011 Hotfix 5.3.0.120 16 June 2011 Removes Skype Extras manager 5.5.0.112 28 July 2011 Skype to Facebook instant messaging New and updated emoticons New login experience Improved call controls Improved video calling reliability Simplified installer flow Avatar selection improved Video snapshot capture improvements Changed group conversations profile area Plus several bug fixes 5.5.0.113 28 July 2011 Resolves Skype login issue for new installations that have UDP blocked on the network Resolves video calling issue on some HP/Palm devices 5.5.0.114 23 August 2011 Hotfix 5.5.0.115 1 September 2011 Hotfix 5.5.0.117 13 September 2011 Adds support for Windows 8 5.6.0.105 29 September 2011 Screen sharing improvements New 'getting started' experience Small changes to the call controls The 'Call Phones' button has been moved Updated 'Click to Call' browser plugins In call advertising Skype Home' UI improvements in compact mode Share your thoughts about this new version on our Support Network or in case you see the odd issue then please report it to us on our public issue tracker. 5.5.0.119 29 September 2011 Updated Skype Click to Call browser plugins Fixed Skype home popping up on compact mode 5.5.0.124 13 October 2011 Removed Google product bundling Added attribution of used third party software 5.6.0.110 13 October 2011 Removed Google product bundling Added attribution of used third party software 5.8 2 February 2012 Full HD video-calling Support for Facebook audio and video-calling (beta) Group screen sharing Hide offline Facebook contacts Push to Talk Skype updater service Bing Bar integration 5.8.0.156 21 February 2012 Hotfix 5.8.0.158 6 March 2012 Hotfix 5.9.0.114 12 April 2012 A new confirmation message when sending a contact to a group conversation A new Hotkey for taking snapshots during video calls Improved non-standard international phone number recognition for Australian users The ability to opt-out from silent updates 5.9.0.115 7 May 2012 Hotfix 5.9.0.123 7 June 2012 Hotfix for Windows 8 release preview 5.10.0.114 14 June 2012 Select and pin your favorite contacts Facebook and Skype contacts combined into one Contacts list Easier to understand premium subscription notices Possibility to control Skype video rendering technology for backward compatibility for people who have trouble with video calls 5.10.0.115 5 July 2012 Hotfix 5.10.0.116 17 July 2012 Hotfix 6.0.0.126 14 October 2012 New design. Six new language packs. Integration with Microsoft accounts (Messenger, Hotmail and Outlook.com). 6.1.59.129 10 January 2013 Integration with Microsoft Outlook to allow initiation of a call or message from within Outlook. New 'add contact' interface. New profile design. 6.2.0.106 13 February 2013 New top toolbar with all major actions together in one place. Send eGift to friend who has a birthday. Added option to send IM with ctrl+enter. Computers with Intel Pentium III or similar CPU’s, which do not support SSE2 instructions, are no longer supported. 6.3.0.105 14 March 2013 Maintenance release. Feature removed: No longer possible for a user to edit another user's message regardless of admin status. Not officially announced. 6.5.0.158 5 June 2013 Improved video, simplified way to add contacts, bug fixes. 6.6.73.106 7 July 2013 Optimizations to the video messaging experience

OS X

OS X Version History

Color Meaning Red Release no longer supported Green Release still supported Blue Future release Version Release Date Features/description 1.4.0.35 19 February 2006 improvement: minor cosmetic changes improvement: more fully localized to Japanese bugfix: calls directed to voicemail sometimes caused glitches in the call drawer 1.4.0.49 5 July 2006 Known issue: Users who created their account on Intel-based computers will not be able to revert to earlier versions of Skype, after they have installed Skype 1.4.0.49. new feature: Universal binary: Skype is now made to run natively on both Intel- and PowerPC-based Mac computers new feature: Web presence: Show your Skype status on the web and in your email signature new language: Traditional Chinese 2.0.0.6 26 October 2006 Make video calls to anyone on Skype, no matter what kind of computer they are using. 2.5.0.85 30 January 2007 ? 2.6.0.72 11 April 2007 Improved audio quality. Transfer calls to your Skype contacts 2.6.0.137 16 May 2007 A new call-transfer feature that is exclusive to the Mac platform. Users can now select More > Call Transfer to transfer an ongoing call to another Skype user on their contact list. Join public chats Chat typing indicator: see when others are writing a message Skype Prime: call a premium-service provider and pay for their advice and knowledge with Skype credit Automatic updates: get new features and updates without having to go to Skype's website DTMF tones for automatic answering services available also during Skype-to-Skype calls 2.6.0.140 22 May 2007 bugfix: USB/Bluetooth Audio update bugfix: Localization fixes bugfix: renamed 'Rename...' to 'Edit Contact...' for SkypeOut contacts bugfix: fixed deleting header files from Skype framework bugfix: fixed crash after forced upgrade 2.6.0.148 13 June 2007 all localizations updated improvement: Skype's own audio codec improvement: Skype improved conference mixer improvement: Skype Jitter Buffer and concealment improvement: Skype audio preprocessing components bugfix: fixed application hangup on handling certain URL links in chat messages bugfix: fixed exception (resulting in disappearance of message) on handling certain intentionally constructed "bad" chat messages bugfix: privacy policy fix, not accepting multichats from non-authorized users 2.6.0.151 17 July 2007 ? 2.6.0.182 27 November 2007 ? 2.7.0.195b 30 November 2007 German, Spanish, French, Dutch, Japanese, Russian, Norwegian, Italian, Czech localizations updated feature: Higher resolution video calls (640×480 and 25 frames per second) feature: Mobile Indicators improvement: Possibility to paste DTMF codes to call window improvement: Added confirmation dialog before closing all open chats improvement: selected chat background color in drawer is now gray if Skype is inactive improvement: Joining public chat when host is offline has improved messaging improvement: clicking search button in the view, which is shown after quickfiltering starts search immediately improvement: "Block" and "Add to Conference" menu items were not enabled when multiple contacts were selected in contact list improvement: Added "Back to Contacts" button to the view, which is shown after quickfiltering didn't find anything improvement: KICKED and KICKBAN messages now shown in chat improvement: Volume slider in conference calls and video calls improvement: Improved context menu of contact groups improvement: Rename contact group right after creation improvement: Address Book contacts are now updated after change in Address Book improvement: context menus of Address Book contacts improved improvement: File transfer notifing window improved improvement: Added "Create New Group" menu item to the "Add to Group" submenu in the context menu of contact list change: Growl removed from advanced prefs change: Renamed 'Show Skype status in menu bar' to 'Show status in menu bar'and moved to General bugfix: Skype did not install Address Book dialler on some instances bugfix: Compatibility with Leopard OSX 10.5 firewall bugfix: Removed 3 seconds delay after hanging up a video call bugfix: When sending contacts to multiple users comma appeared between user bugfix: Sound popup menu was not updated after removing custom sound bugfix: Video calls were unstable on PowerPC computers bugfix: Kick chat messages was displayed incorrectly bugfix: Crash on quitting with Cmd+Q before user is signed in bugfix: "About Skype" window did not close when the logo was clicked bugfix: It was not possible to send voicemails after cancelling a voicemail recording right after it started bugfix: Number of missed events were wrong sometimes after marking new voicemails bugfix: Sometimes contact list was not fully visible or there was some white space inside the main window bugfix: Sometimes echo123 was not added to the contact list for the new users signing in first time bugfix: Skype crashed during processing transfer history for File Transfer window bugfix: Sometimes Skype crashed when stopping video bugfix: File Transfer didn't show correct file size during transfer bugfix: Local video was not shown on some cases bugfix: Search button in Find Contact was disabled bugfix: It was possible to import duplicate phone numbers bugfix: It was not possible to accept file transfer after Skype client restart bugfix: Multichat participants list was wrongly sorted bugfix: There was no call window on receiver side, if caller hung up and called again very quickly bugfix: If someone came online while renaming a contact the whole contact name got selected bugfix: Contact groups were sometimes expanded automatically when internet connection status changed bugfix: Busy signal kept playing while waiting for redial bugfix: Chats did not open sometimes on Panther OSX 10.3.9 bugfix: Reseting language in edit profile window did not work bugfix: Sometimes Skype played dual ringtones when making a SkypeOut call bugfix: It was not possible to transfer call back to the person who transferred it to you bugfix: Wrong chat was selected in drawer after closing all read bugfix: When adding Address Book contact to Skype contact list some details were not added to contact list bugfix: Sometimes Skype froze while loading contactlist right after sign-in bugfix: Conference call view didn't transform back into single call view, when only one participant was left in the call bugfix: Full screen video didn't clear when joining a conference call bugfix: Long URL's were overdrawn in view profile window bugfix: When already in a call, and 'automatically answer calls' selected – current call was placed on hold and incoming call was answered bugfix: Cancel Sign In button didn't function properly bugfix: Skype API: OPEN CHAT command didn't work 2.6.0.184 4 December 2007 ? 2.7.0.257 13 February 2008 ? 2.7.0.330 15 May 2008 improvement: added NAT-PMP support improvement: added uPnP support improvement: added Authenticated Proxy support bugfix: 3–4 second delay when hanging up video call bugfix: sometimes Skype crashed when applying changes in Edit Profile window bugfix: "Add to Contacts" command was not working for 1-on-1 chats in history view bugfix: "Add to list" button was cut off in Start Conference and Add Users to Chat windows on Tiger bugfix: Safari 3.1 (4525.13) chats time-name were getting cut off. bugfix: Abnormal exit on declining two sent files. bugfix: Add and remove buttons were cut off in Send Contacts window on Leopard bugfix: Add to Contacts command didn't work in the context menu of the history list bugfix: Address Book phone numbers with custom tags were not shown in Skype bugfix: Call Transfer menu not updating when new contacts were added bugfix: Chats were losing their topics bugfix: crash/hangup on skype credit change when old SMS chats open for long time bugfix: default call window height was too small bugfix: do not add chats without activity timestamp to event history bugfix: fix for delayed sms delivery notifications bugfix: flag icons not showing in upper case bugfix: Freeze with lots of Address Book contacts (>3000) bugfix: history entries became blank when right-clicked on Leopard bugfix: Improvements to audio sync bugfix: it was not possible to use the context menus of conference call participants when the call was muted or on hold bugfix: it was possible to change the value of sound level indicators in conference calls bugfix: Leading 0 was removed when user tried to call to Italian landline number – they need leading 0 bugfix: missed events badge was missing from chat drawer after Skype restart bugfix: outgoing calls that went to voicemail didn't have icons in the history view bugfix: own voice level indicator was still moving when conference call was muted bugfix: Skype crashed after "Delete all SMS Messages" was pressed bugfix: sometimes Skype got stuck in the login process when Address Book integration was enabled bugfix: sometimes window artifacts appeared when having two simultaneous calls bugfix: Status does not reset correctly after screensaver triggers away if Set my status to Away when inactive for 0 minutes was set bugfix: strange sound start happening on end of the call (Apple Bug ID# 5796436) bugfix: when being signed in on at least two Macs and answering a call on one machine, then ringing didn't not stop on the second machine bugfix: When chats are closed after draging them around, wrong chat gets activated bugfix: when placing a call, then sometimes the word "Button" was briefly displayed instead of the phone number bugfix: Word wrap in Public chat settings window bugfix: Workaround for strange large number startTimestamp on some chats (preventing chat history links displaying) bugfix: yellow alert were hiding chat topics quite often. change: replaced SkypeIn with Online Number change: increased minimum size of SkypeOut Caller Window change: new User Registration Window: By default, eMail notifications checked change: pop-up dialog to enable or disable Address Book integration change: sometimes duration of some calls was displayed as 1193 hours in the call history change: sound event for contact coming online is now off by default Skype API: BTN_RELEASED NO clears quickfilter field now (previously removed the last character only) 2.8.0.438 9 April 2009 localizations updated change: spectator window for screen sharing change: My Account page embedded in the client bugfix: Skype didn't hide on OS X login bugfix: copy/paste from chats was not working correctly bugfix: sometimes Skype froze for a couple of seconds when starting or stopping screen sharing bugfix: screen sharing windows could be left on screen when a call was joined to a conference bugfix: PiP didn't appear in full screen when receiving screen sharing bugfix: the overlay didn't appear for fullscreen screen sharing and then the exit fullscreen button didn't work bugfix: fullscreen mode would exit after a held call was resumed bugfix: call could not be ended after being redirected to voicemail bugfix: the call window layout was broken if the dialpad was shown during a video call bugfix: URLs inside brackets were not clickable bugfix: sometimes Skype crashed after deleting missed events without reading them bugfix: sometimes Skype Access sessions were not terminated properly bugfix: sometimes Skype Access session durations were not displayed accurately bugfix: sometimes extending a Skype Access session didn't work as expected bugfix: after signing in as another user, it was not possible to start a Skype Access session bugfix: it was possible to start a new Skype Access session before previous one had finished bugfix: Start Skype Access menu item was disabled when not signed in bugfix: Skype Access session appeared in red after extending the session bugfix: sometimes there were two controversial messages about Skype Access availability bugfix: sometimes Skype crashed when leaving a chat bugfix: history was not picking up display names from Address Book for text messages bugfix: text on screen sharing selection buttons was misaligned on Tiger bugfix: warning icon was not removed after extending online number bugfix: after auto-recharge, balance pane had space on the right bugfix: fixed enabling of Quick Add button in text-only toolbar mode bugfix: sometimes (null) was added as a SkypeOut display name instead of the one specified bugfix: ESC key now closes emoticon roster as it should bugfix: fixed text positioning on Tiger for screen sharing selection window buttons bugfix: if remote contact cancels a file transfer then sometimes it still appeared as pending on the receiver side bugfix: do not set to status to away during screensaver when auto away is set to 0 minutes bugfix: the PiP video could draw over Mute/Hold/Transfer overlays bugfix: fixed video toolbar button enabling for the case where there is no camera or video is disabled bugfix: fullscreen button and PiP views did not appear on Panther and Tiger if "keep call windows in front" option was turned on bugfix: fullscreen view was not displayed correctly when entering full screen from the screen sharing spectator window bugfix: multiple call windows were left open when calls failed bugfix: call overlay window could appear without the call window if the call window was minimised while the other party was starting video bugfix: fixed window resizing issues when the other party was starting and stopping video, which occurred because the wrong window sizes were being stored in defaults bugfix: call window would resize incorrectly when the call was put on hold then resumed bugfix: the call window's fullscreen button could end up in the wrong position when exiting full screen while receiving screen sharing bugfix: call window resizes when entering and exiting full screen mode while receiving screen sharing bugfix: emoticon button rendered before the chat window bugfix: fixed double free error when exiting fullscreen using the escape key bugfix: fixed crash on chat close because overlay window was being double deallocated bugfix: fixed incorrect call window layout, which sometimes occurred if the connection was dropped bugfix: window did not resize correctly when showing the dialpad (it could extend offscreen) if the computer had multiple displays bugfix: dialpad was not shown when exiting full screen bugfix: fixed bad volume slider layout in call window, which could occur when answering a video call during an existing video call bugfix: fixed exception being thrown because emoticon button was observing a dealloced chat bugfix: fixed Quick Add window positioning when item was not first in the toolbar bugfix: the Quick Add toolbar item appears pressed in all chat windows bugfix: the dialpad could expand partially offscreen when it was shown, by moving the call window fully onscreen after the dialpad is shown bugfix: the call window layout was broken if the toolbar was shown or hidden during a video call bugfix: when assigning multiple contacts to groups screen refreshing was very slow bugfix: adjusted layout of Quick Add window and make sure it doesn't run under the Dock when it's on the left or right bugfix: added limits to the maximum width of the slider in the call window bugfix: removed a small visual glitch after reducing size of contact list bugfix: fixed small problem with rendering flags in chat bugfix: after restart, second chat window didn't remember its size and position bugfix: prevent the user from calling their own online number bugfix: chat window was not closed after database mount error improvement: added Retry button to the Skype Access window improvement: consistency with other Mac apps: added shortcut for Show Offline Contacts, moved Make Text commands to View menu, use Clear instead of *Delete wording improvement: improved enabling of the video and screensharing buttons based on the receiver's capabilities improvement: improved toolbar button image rendering improvement: improved new chat handling improvement: some string adjustments improvement: some internal optimizations and improvements Skype API: implemented get skypeversion Skype API: implemented: get chat x dialog_partner Skype API: open options command only accepted uppercase properties Skype API: implemented ping 2.8.0.659 20 July 2009 Hotfix 2.8.0.772 14 September 2009 Hotfix 2.8.0.722 21 September 2009 Skype Access: An incorrect notification message appeared "This WiFi hotspot does not support Skype Access" when users tried to connect to Skype Access when Airport was set to off. Chat: Text was not visible within the chat input field that contained a certain Unicode character. Contacts: Platform specific Skype for Mac OXS 10.3 (Panther); Skype froze after deleting unread missed events. Contacts: Mood message appeared blank after playing iTunes. Contacts: Contacts were still visible in the "Manage Contact Groups" after deleting them from the Contact List. Video: Video appeared blank between Skype for Windows and Skype for Mac. Video: A video error message appeared at the beginning of a video call. Video: Video and screen sharing functionality did not work after a multichat Screen Sharing: Recipients screen remained black after screen sharing was resumed. Screen Sharing: A green line appeared when screen sharing between Skype for Windows and Skype for Mac OXS 10.4 (Tiger). Screen Sharing: Skype froze when screen sharing between Skype for Windows and Skype for Mac. Miscellaneous: An incorrect informative message appeared when entering more than 20 characters for a password. Miscellaneous: The Show in Finder option was not available after cancelling a file transfer. Miscellaneous: Platform specific OSX 10.3 (Panther); Skype could not connect to the network. Skype froze when selecting "Quit Skype". Miscellaneous: The typing indicator appeared within a multichat even though no one was typing. Miscellaneous: An incorrect informative message appeared when trying to call an emergency number. Miscellaneous: Commas were not visible in mood messages. Miscellaneous: A users name and password field appeared blank after selecting the option "Remember my name and password on this computer". SMS: An error message appeared when dragging and dropping a participant to an SMS group. SMS: An error message appeared when closing the SMS window after sending to multiple recipients. SMS: SMS functionality did not recognize newly updated telephone numbers associated to Skype Out contacts. SMS: Ringing sound was not available on incoming calls. 2.8.0.851 8 February 2010 Fixes issues 2.8.0.863 29 October 2010 Fixed login issues to Skype 2.8.0.866 17 November 2010 This was the most recent version that could run on the Power PC architecture. 5.0.0.7994 8 February 2011 ? 5.1.0.914 24 March 2011 Hotfix 5.1.0.922 14 April 2011 ? 5.1.0.935 9 May 2011 Security updates Resolves video freezing in high-packet loss networks Fixes minor bugs 5.1.0.968 1 July 2011 ? 5.2.0.1523 5 July 2011 Improved Multi-tasking Group Screen Sharing Sidebar enhancement Support for Mac's built-in HD and Logitech's B910 HD cameras Minor bug fixes 5.2.0.1572 26 July 2011 Updated localizations The removal of "Professional Account" Minor improvements 5.3.0.1074 8 August 2011 Updated contact list view New contact grid view Support for OS X Lion Minor improvements 5.3.0.1093 1 September 2011 Sometimes Skype crashed during video calls Fixes a problem in Norwegian localization, which could lead to client freeze 5.4.0.1217 15 September 2011 Facebook connect Facebook chat Skype Home Improved video quality Minor bug fixes 5.4.0.1771 17 November 2011 Facebook video calls 5.5.0.2069 12 January 2012 Improved Call UI Accept incoming call with video Improvements in quality and stabilization 5.6 6 March 2012 Automatic Updates Improved UI for group video calling New full screen mode in OS X Lion Ability to delete conversations Ability to disable Audio Gain Control 5.7 12 April 2012 ? 5.7 9 May 2012 Hotfix 5.8 14 June 2012 More Compact Contacts Monitor Improved Screen Sharing (Premium) OS X Mountain Lion Ready Resizable Contact List Columns Improved SMS Usability Improved automatic reorientation of mobile video calls Keyboard shortcut for Volume Control Full HD video-calling 6.0 24 October 2012 Microsoft and Facebook Account Integration Ability to message Messenger users Ability to call Messenger users Localised into six more languages Removal of online user count Display previously created profile pictures New user interface Ability to Open Chats in Multiple Windows Retina Display Support 6.1 10 January 2013 ClicktoCall - Ability to call from Safari Improved profile view 6.2 13 February 2013 Ability to send eGifts Ability to send SMS without verification 6.3 13 March 2013 Slideshow of other participants in a group call New In-Call DTMF dial pad 6.4 15 May 2013 Infinite chat scrolling Improved find from a chat conversation Improved file transfer Improved send and receive contacts Support for Simplified Chinese OS X 10.6 or later is required

Linux

Linux Version History

Color Meaning Red Release no longer supported Green Release still supported Blue Future release Version Release Date Features/description 0.90.0.3 21 June 2004 first public beta 1.0 1 February 2005 first stable version 1.1.0.13 25 May 2005 ? 1.2.0.11 July 2005 ? 1.2.0.17 2005 ? 1.2.0.18 ? ? 1.2.0.21 ? ? 1.3.0.30 28 June 2006 sound system upgrade and more 1.3.0.37 17 August 2006 beta 1.3.0.50 27 September 2006 beta 1.3.0.53 4 October 2006 stable 1.3.0.57 ? ? 1.4.0.xx 2 May 2007 ? 1.4.0.xx 23 May 2007 ? 1.4.0.xx 14 June 2007 ? 1.4.0.94 1 August 2007 improved audio 1.4.0.xx 4 October 2007 ? 2.0 7 November 2007 video is here 2.0.x 6 February 2008 ? 2.0.x 13 March 2008 ? 2.1 26 August 2009 ? 2.1.0.81 21 January 2010 ? 2.2 6 April 2011 ? 2.2.0.35 7 June 2011 ? 2.2.0.99 14 May 2012 libpng related security update 4.0 14 June 2012 New Conversations View, new Call View, removed multiple instances support. 4.0.0.8 17 June 2012 4 bugs fixed 4.1 15 November 2012 Integration with Microsoft Accounts (Messenger, Hotmail and Outlook.com).

Security and privacy

Main article: Skype security

Skype is claimed to be a secure communication, with one of its early web pages stating "highly secure with end-to-end encryption". Security services are invisible to the user, and encryption cannot be disabled. Skype reportedly uses publicly documented, widely trusted encryption techniques: RSA for key negotiation and the Advanced Encryption Standard to encrypt conversations. However, it is impossible to verify that these algorithms are used correctly, completely and at all times as there is no public review possible without a protocol specification and/or the program source code. Skype provides an uncontrolled registration system for users with no proof of identity. Instead, a free choice of nicknames permits users to use the system without revealing their identity to other users. It is trivial to set up an account using any name; the displayed caller's name is no guarantee of authenticity. A third party paper analyzing the security and methodology of Skype was presented at Black Hat Europe 2006. It analyzed Skype and found a number of security issues with the current security model.

Skype incorporates some features, which tend to hide its traffic, but it is not specifically designed to thwart traffic analysis and therefore does not provide anonymous communication. Some researchers have been able to watermark the traffic so that it is identifiable even after passing through an anonymizing network.

In an interview Kurt Sauer, the Chief Security Officer of Skype, said, "We provide a safe communication option. I will not tell you whether we can listen or not." Skype's client uses an undocumented and proprietary protocol. The Free Software Foundation (FSF) is concerned by user privacy issues arising from using proprietary software and protocols and has made a replacement for Skype one of their high priority projects. Security researchers Biondi and Desclaux have speculated that Skype may have a back door, since Skype sends traffic even when it is turned off and because Skype has taken extreme measures to obfuscate their traffic and functioning of their program. Several media sources reported that at a meeting about the "Lawful interception of IP based services" held on 25 June 2008, high-ranking unnamed officials at the Austrian interior ministry said that they could listen in on Skype conversations without problems. Austrian public broadcasting service ORF, citing minutes from the meeting, reported that "the Austrian police are able to listen in on Skype connections". Skype declined to comment on the reports. One easily demonstrated method of monitoring is to set up two computers with the same skype userid and password. When a message is typed or a call is received on one computer, the second computer duplicates the audio and text. This requires knowledge of the userid and password.

The United States Federal Communications Commission (FCC) has interpreted the Communications Assistance for Law Enforcement Act (CALEA) as requiring digital phone networks to allow wiretapping if authorized by an FBI warrant, in the same way as other phone services. In February 2009 Skype said that, not being a telephone company owning phone lines, it is exempt from CALEA and similar laws, which regulate US phone companies, and in fact it is not clear whether Skype could support wiretapping even if it wanted to. According to the ACLU, the Act is inconsistent with the original intent of the Fourth Amendment to the U.S. Constitution; more recently, the ACLU has expressed the concern that the FCC interpretation of the Act is incorrect. It has been suggested that Microsoft made changes to Skype's infrastructure to ease various wiretapping requirements; however, Skype denies the claims.

On 20 February 2009 the European Union's Eurojust agency announced that the Italian Desk at Eurojust would "play a key role in the coordination and cooperation of the investigations on the use of internet telephony systems (VoIP), such as 'Skype'. ... The purpose of Eurojust’s coordination role is to overcome the technical and judicial obstacles to the interception of internet telephony systems, taking into account the various data protection rules and civil rights"

In November 2010, a flaw was disclosed to Skype that showed how hackers could secretly track any user's IP address. As of 2013, this still has not been fixed.

In 2012, Skype introduced automatic updates to better protect users from security risks, but received some challenge from users of the Mac product, as the updates cannot be disabled from version 5.6 on, both on Mac OS and Windows versions, although in the latter, and only from version 5.9 on, automatic updating can be turned off in certain cases.

According to a 2012 Washington Post article, Skype "has expanded its cooperation with law enforcement authorities to make online chats and other user information available to police"; the article additionally mentions Skype made changes to allow authorities access to addresses and credit card numbers.

In November 2012, Skype was reported to have handed over user data of a pro-Wikileaks activist to Dallas, Texas-based private security company iSIGHT Partners without a warrant or court order. The allegation was an apparent breach of Skype's privacy policy. Skype responded with a statement that it launched an internal investigation to probe the breach of user data privacy.

13 November 2012, a Russian user published a flaw in Skype's security, which allowed any person to take over a Skype account knowing only the victim's email by following 7 steps. This vulnerability was claimed to exist for months, and existed for more than 12 hours since published widely.

14 May 2013, it was documented that a URL sent via a Skype instant messaging session was usurped by the Skype service and subsequently used in a HTTP HEAD query originating from an IP address registered to Microsoft in Redmond (the IP address used was 65.52.100.214). The Microsoft query used the username and password supplied in the IM conversation, and was generated by a previously undocumented security service. Security experts speculate the action was triggered by a technology similar to Microsoft's SmartScreen Filter used in its browsers.

The US intelligence agency National Security Agency (NSA) can monitor Skype user behavior (email, chat, uploads, downloads) of all non-US persons outside the US through their surveillance program PRISM which requires FISA court authorization.

In 2013, as part of the 2013 mass surveillance scandal it was revealed that agencies such as the NSA and the FBI have the ability to eavesdrop on Skype.

Service in the People's Republic of China

Since September 2007, users in China trying to download the Skype software client have been redirected to the site of TOM Online, a joint venture between a Chinese wireless operator and Skype, from which a modified Chinese version can be downloaded. The TOM client participates in China's system of Internet censorship, monitoring text messages between Skype users in China as well as messages exchanged with users outside the country. Niklas Zennström, then chief executive of Skype, told reporters that TOM "had implemented a text filter, which is what everyone else in that market is doing. Those are the regulations." He also stated: "One thing that’s certain is that those things are in no way jeopardising the privacy or the security of any of the users."

In October 2008, it was reported that TOM had been saving the full message contents of some Skype text conversations on its servers, apparently focusing on conversations containing political issues such as Tibet, Falun Gong, Taiwan independence, and the Chinese Communist Party. The saved messages contain personally identifiable information about the message senders and recipients, including IP addresses, usernames, land line phone numbers, and the entire content of the text messages, including the time and date of each message. Information about Skype users outside China who were communicating with a TOM-Skype user was also saved. A server misconfiguration made these log files accessible to the public for a time.

Localization

Skype currently comes bundled with the following locales and languages: Arabic, Bulgarian, Catalan, Chinese (Traditional and Simplified), Croatian, Czech, Danish, Dutch, Estonian, Finnish, French, German, Greek, Hebrew, Hungarian, Indonesian, Italian, Japanese, Korean, Latvian, Lithuanian, Norwegian, Polish, Portuguese (Brazilian and European), Romanian, Russian, Serbian, Slovak, Slovenian, Spanish, Swedish, Thai, Turkish, Ukrainian and Vietnamese.

As the program (on Windows) offers users the option of creating new language files, at least 31 other (full or partial) localizations are also available for the following languages: Adyghe, Afrikaans, Albanian, Aragonese, Armenian, Basque, Belarusian, Bosnian, Breton, Chuvash, Cornish, Erzya, Esperanto, Faroese, Georgian, Irish, Khmer, Ligurian, Macedonian, Mirandese, Nias, Nynorsk, Palatinate German, Persian, Scottish Gaelic, Tajik, Tamil, Telugu, Uyghur (Persian and Latin script), Welsh

Customer service

As of February 2012, Skype provides support through their web support portal, support community, @skypesupport on Twitter, and Skype Facebook page. Direct contact via email and live chat is available through their web support portal. Chat Support is a premium feature available to Skype Premium and some other paid users.

In January 2010 Skype rescinded their policy of seizing funds in Skype accounts that have been inactive (no paid call) for 180 days. This was in settlement to a class action lawsuit. A settlement of up to US$4 was paid to persons who opted into the action.

Skype's refund policy states that they will provide refunds in full if a client has used less than 1 euro of their Skype Credit. "Upon a duly submitted request, Skype will refund you on a pro rata basis for the unused period of a Product".

Skype has come under some criticism from users and as well for the inability to close accounts. Users not wanting to continue using Skype can make their account inactive by deleting all personal information, except for the user name.

Educational use

Although Skype is a commercial product, its free version is being used with increasing frequency among teachers and schools interested in global education projects. For example Skype is being used to facilitate language exchange. Students in different parts of the world are paired off, each is a native speaker of the language that the other wishes to learn. In conversations over Skype they alternate between the two languages.

Teachers are using Skype in unique ways to fulfill educational goals. The videoconferencing aspect of the software is valuable in that it provides a way to connect students who speak different languages, hold virtual field trips, and reach out to experts in varying fields of study. These experiences allow students a chance to apply what they are learning in the classroom to real-life experiences and it also achieves further learning opportunities.

Skype in the classroom is another free tool that Skype has set up on their website. It provides teachers with a way to make their classrooms more interactive and interesting. Skype in the classroom is a service that teachers can sign up for that will allow students to meet other students, talk to experts, and share ideas. Teachers can collaborate with other teachers around the world and design different learning experiences for their students. There are various Skype lessons, in which students can participate. Teachers can also use Skype’s’ search tool and find experts in the field of their choice.

Outages and downtime

On 16 August 2007, Skype became unavailable for two days to a majority of its users. Millions of users were requesting to log-in at the same time following a routine Windows Update and this flooded the peer-to-peer system.

On 22 December 2010, it was reported that Skype experienced an outage estimated to represent 8 million foregone calls. Skype administrators placed the following message on their Twitter page: "Some of you may have problems signing in to Skype – we're investigating, and we're sorry for the disruption to your conversations...engineers and site operations are working non-stop to get things back to normal." The problem came down to the limited availability of "supernodes", affecting some versions of Skype. Later in the day, Skype's CEO, Tony Bates, issued an apology. He said that the matter was being taken very seriously and was being thoroughly investigated. He said that malicious attack was not being ruled out as a problem cause and he put his estimate of the foregone calls at about 10 million. On 23 December 2010, Skype's blog with Tony Bates issued another apology through a video posted on YouTube for the Skype outage.

The problem persisted across the North America, Latin America, Europe and Asia. It had started to subside by 8:30 pm UTC; however users were warned it might take several hours for the program to be fully operative again. It was reported at 9:27 am 23 December UTC that most users were able to log in again although some still could not. On the other hand into Thursday only about a third of the expected traffic was actually using Skype, relative to the time-period. On 23 December 2010, Skype said on its blog that the system had stabilized, and a detailed explanation of the incident was published six days later. Bates offered all Pay As You Go and Pre-Pay customers a free call to any landline as compensation. Subscribers had their subscription extended by one week.

Open source alternatives

Open source alternatives to Skype include Jitsi and Ekiga. These multiplatform clients can encrypt chats, calls and video calls. Users are required to register an XMPP account to use the software.

See also

• Caller ID spoofing
• Comparison of instant messaging clients
• Comparison of instant messaging protocols
• Comparison of VoIP software
• Mobile VoIP
• Presence information
• Secure communication
• Unified communications

References

Further reading

• Rushe, Dominic. "Skype's secret Project Chess reportedly helped NSA access customers' data." The Guardian. June 20, 2013.
• Latest Products."Skype Launches Video Messaging For Free

External links

• Official website
• Compilation of research and technology articles involving Skype
• An Experimental Study of the Skype Peer-to-Peer VoIP System
• "Skype, Going Public, Hopes for $100 Million From First Offering" Eric Pfanner, The New York Times, 9 August 2010
• Skype Journal, an independent blog covering Skype since its 2003 launch.