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Basic data

developer Mail.Ru Group
Publishing year November 15, 1996
Current  version 10.0 build 12414
operating system Windows XP , Vista , 7 , 8 , 10 , macOS , Linux , Android , iOS , Windows Phone
programming language C ++
category Instant messaging
License Adware
German speaking Yes

ICQ ( homophone for English I seek you , I look for you ' ) is an instant messaging - service , which from 1998 to the US company AOL owned and was sold in April 2010 to Russia. The owner is now the Russian investment company Mail.Ru Group (formerly Digital Sky Technologies). Users can use it to chat with one another over the Internet or send time-shifted messages. The proprietary network protocol used , but disclosed by AOL, is called OSCAR . ICQ was criticized as adware because, among other things, it manipulated the browser home page and search engine without the consent of the user. ICQ version 10.0 was released on March 17th, 2016.

ICQ 7: login window


The first ICQ software was released in November 1996 by the Israeli startup company Mirabilis . It was developed by the four Israeli students Yair Goldfinger , Arik Vardi , Sefi Vigiser and Amnon Amir . ICQ, which is regarded as the first Internet-wide instant messaging service in today's sense, spread rapidly because there was no comparable software on the market that only required Internet access and the program was available free of charge.

“None of us had a job. What should we do? Wait until someone hires us or do something yourself? "

- Yair Goldfinger

America Online ( AOL ) bought Mirabilis in June 1998 for $ 407 million. At the beginning of the millennium, ICQ had a user base of well over 100 million, making it the market leader in instant messaging. On December 19, 2005, AOL Time Warner announced that ICQ had been awarded a patent for instant messaging.

The current version of the software runs under Windows XP and higher as well as under macOS . The last version that can run under Windows 98 and 2000 is ICQ 5.1, which was no longer supported as of 2007.

Version 7.2 was released on January 9, 2010. At the end of April 2010, it was announced that AOL had sold ICQ to the Russian investment company Digital Sky Technologies for $ 187.5 million. In September 2010, the company changed its name from Digital Sky Technologies to Mail.ru Group . This year ICQ still had 42 million users.

Version 7M was released on May 2, 2012.

From January 2009, ICQ made an app of the messenger available for mobile use on Apple's iPhone for the first time. An app version followed in July 2010 for Android and in March 2012 for Windows Phone , in April 2012 the versions for iOS and Android were updated so that photos and your own location can be shared with other users and messages can also be shared in offline mode can be read and written.

However, with the establishment of social networks such as Facebook or Twitter and the WhatsApp messenger belonging to Facebook Inc. , the number of active ICQ users has fallen sharply. As of 2013, ICQ still had 11 million users.

Version 10.0 was released on March 17, 2016. Since this version, the chat history has been synchronized, group and video chats are now possible and files up to 4 GB can be sent.

Since December 28, 2018, ICQ no longer supports the old OSCAR protocol, which means that alternative clients such as B. Pidgin can no longer be used for ICQ.

Since the relaunch on April 7, 2020, the service has been run under the name ICQ New.

ICQ numbers

A user is identified using his ICQ number or ICQ UIN. UIN is an abbreviation for Unique Identification Number , in German: Unique identification number . A UIN is assigned during registration and is password-protected.

In 2009, over 470 million users were registered with ICQ. However, this was not the actual number of active users, as users can have multiple numbers and the registration does not say anything about actual, active use.

The number sequence of the ICQ UINs starts with 10,000, increases continuously and currently (as of June 22, 2010) has nine digits. Six-digit ICQ numbers are a rarity and at that time were sold on the Internet for amounts up to 250 euros. Only developers of the ICQ software have five-digit ICQ numbers, but at that time they were occasionally offered at online auctions for several hundred euros.

Due to the increasing theft of short or particularly attractive ICQ UINs by means of phishing or brute force attacks, Mirabilis responded in 1999 with an improvement to the ICQ Password Retrieval System , which sends the password of a UIN to the primary email address entered in the profile . Since then, e-mail addresses that have been changed by hackers, for example, have also been saved. This makes it possible to get back a stolen ICQ UIN with a falsified primary e-mail address after it has been stolen (or after it has been purchased from an online auction house, for example). Only ICQ UINs that were never associated with an email address before or only before 1999 are excluded from this option. This trick is occasionally used on unsuspecting ICQ UIN buyers.

AOL offers users who have an ICQ number the service of registering an email address with the ending “@ icqmail.com” free of charge. For a while now, ICQmail and AIM have merged their e-mail services. Old e-mails were not accepted, but the memory limit was lifted.

Special ICQ numbers

AOL operated a bot under the ICQ number 12111 with the nickname ICQ System . All users with ICQ 6 or ICQ 5.1 automatically had this bot in their contact list. In the case of alternative clients, you were usually asked whether you would like to add the user.

Other special numbers are: 10000 (Москва Кремль - Moscow Kremlin ) and 10111 (ICQ system).

Features of the software


  • Lite version: more modern than the Pro version and equipped with Xtraz . In contrast to ICQ Pro, ICQ Lite is available in many languages.
  • ICQ2Go : The official Java applet ICQ2Go! can be operated from any PC on which a browser that supports Java or Flash is installed , even if there is no other ICQ software on the PC. It only supports sending SMS and text messages, but is particularly useful in Internet cafes or on other people's PCs. You can access it worldwide via the Internet and thus chat with people from anywhere. The Flash version of ICQ2Go was renewed in mid-June 2008 and now offers RTF messages from ICQ6, a new, more modern design and allows the use of ICQ6 status messages.
  • Pro version: contains many functions. ICQ Pro is only available in English and is no longer being developed. The last version is ICQ Pro 2003b from October 23, 2003.
  • ICQ 5 : ICQ Voice Chat, Push2Talk etc.
  • ICQ 6 : Released April 17, 2007.
  • ICQ 6.5 : Released on November 27, 2008 and supplements ICQ 6 with so-called "Open Xtraz". ICQ 6.5 is currently available in ten languages. In addition to the "official" ICQ 6.5, there are several partner versions, including ProSieben and Sat.1 . ICQ 6.5 is currently the only ICQ version (after 2006) in development.
  • ICQ 7 Lite : A version that is currently only available on the Russian market, but can also be used in Germany with the help of a patch .
  • ICQ 7 : Released on January 19, 2010. In addition to a new design, the new features include the link to online communities such as Facebook and Twitter .
  • ICQ 10.0 : Released March 17, 2016.
  • ICQ for iPhone  - The program is offered in the iTunes Store .
  • ICQ for Blackberry  - Can only be purchased exclusively through the Blackberry.
  • ICQ for Windows Mobile  - GM (v1.0.23.1): Released November 3, 2009. Version for Windows Mobile .
  • ICQ for Mac and ICQ for Linux  - Versions implemented in Adobe AIR for computers with Linux and Mac operating systems. Since the end of May 2011, it has been possible to use an official ICQ client under Linux for the first time. For Mac operating systems, there was previously only one version that had not been changed since 2002.

Versions older than ICQ 6 can no longer be used, as the connection establishment is rejected by the server.


While the appearance of ICQ could already be changed in early program versions using additional software, AOL implemented real support for so-called skins for the first time in the five-version version . Although the range of official skins is very limited, ICQ users have discovered the possibility and have started to create their own, compatible skins with the SkinBuilder software . These .skn files are copied to the Skins folder of the ICQ installation and then activated in the program settings. In addition, various ICQ editions, for example the ProSieben edition or the Sat.1 edition, contain their own skins.

From version 6 the software is based on a new environment structure ( Boxely ), which enables users to create their own skins. These come as so-called packages in a folder called Packages , which is located in the installation directory of ICQ 6 .

From version 7 the user can have ICQ displayed in any color. No packages or additional software need to be loaded for this.


The Lite version of ICQ contains additional functionalities, so-called Xtraz . With this ICQ follows the trend that Microsoft started with Windows Live Messenger and Yahoo with Yahoo Messenger (actually Yahoo! Instant Messenger ) to offer more than just instant messaging.

These include:

  • Various games that can be played alone or in pairs, for example pool ( pool simulation with points system), checkers , backgammon (with points system), Warsheep (tactical round strategy game ), Connect Four , Slide-a-lama (in the style of four wins held round game), RPS (Rock-Paper-Scissors; in German scissors, stone, paper ) and Zoopaloola .

With version 5 the following were added:

"Open Xtraz"

Open Xtraz are small applications that ICQ users can develop themselves. The first available Open Xtraz include, for example, “See Too” for viewing videos together, the “pazAlbum” photo album or the “ICQ Favorites” bookmark management.


The ICQ protocol called OSCAR is based on TCP . After Mirabilis was bought by AOL, the ICQ protocol was heavily adapted to the AOL Instant Messenger protocol. The ICQ numbers are now stored internally as screen names. This measure makes it possible to contact users of the other messenger with both messengers.

The ICQ transmission protocol is changed from time to time, as a result of which clients from third-party manufacturers usually have connection problems. A change was made in February 2006, for example, which caused problems for Trillian and Miranda IM to receive messages. However, updates for the two clients that fixed the problem were provided a few days later. The original software and other alternate clients were not affected by this change.

Another problem is that version numbers of older clients are sometimes banned via the official server. However, this also applies to alternative clients, as these must pretend to be a certain version of the original ICQ client. This was carried out on July 11, 2006 with particular severity, after which a large number of alternative clients could no longer connect. With a minimal program change (update of the transferred client information) such problems can be solved in a very short time.

On May 28, 2008, a profound change was made to the login process , which means that from this point in time the login was only possible together with an MD5 check sum. Therefore, many alternative clients, but also all ICQ versions lower than six, could no longer connect to the ICQ network. The problem with alternative clients can be eliminated by activating the "secure login". Users of earlier ICQ versions (before ICQ 6) could log in with their data again after a few hours.

ICQ started a test with the open XMPP protocol , but stopped testing at the beginning of 2008 after it became known.


Data protection in the terms of use

In the usage rules established by the operator ICQ Inc. on June 7, 2000, the user waives all his or her intellectual property rights to the data made accessible via the ICQ service. This is the case, for example, when sending information and files through instant messaging.

Extract from the terms of use:

“You agree that by posting any material or information anywhere on the ICQ Services and Information you surrender your copyright and any other proprietary right in the posted material or information. You further agree that ICQ Inc. is entitled to use at its own discretion any of the posted material or information in any manner it deems fit, including, but not limited to, publishing the material or distributing it. "

“You agree that by posting, you are giving up your copyright, as well as any other property rights in any material broadcast. You further agree that ICQ Inc. is authorized, in its sole discretion, to use any material or information posted in any way, including, but not limited to, posting or distributing the material. "

In the "Privacy Policy" ( Privacy Policy ) states, however:

"Your ICQ Services Information will not be shared with third parties unless: - You have published such information in Public Areas ..."

"Information about your ICQ services will not be passed on to third parties unless you have published this information in publicly accessible areas."

However, the above paragraph refers to ICQ Service Information, which is defined as follows:

"When you register with and / or use the ICQ Services, you may provide ICQ with, or ICQ may otherwise obtain personally identifiable information (your" ICQ Services Information ")."

"When you register with ICQ and / or use the ICQ services, it is possible that you provide ICQ with personal information or that ICQ receives this information in another way (your" ICQ services information ") . "

This paragraph therefore only relates to the information that the user provides about himself or that ICQ collects about the user. However, it does not apply to the content of instant messaging messages. It is therefore unclear what the situation is about the confidentiality of the content of IM messages. ICQ reserves the right to make this data available to law enforcement authorities.

Use of alternative clients

ICQ does not permit the use of its services via other client software, excerpt from the end user license agreement :

“You agree not to (1) create or use any software other than the software provided by ICQ or by America Online, Inc., or any affiliate thereof, to enter your ICQ number and password or to access the ICQ Services, without the express written authorization of ICQ; (2) extract information from the ICQ Services, reverse engineer, decompile, disassemble, alter, duplicate, make copies, create derivative works from, distribute or provide others with the software, the ICQ communications protocol or any information available on, derived or extracted from the ICQ Services, or any part thereof; (3) block, disable or otherwise affect any advertising, advertisement banner window, links to other sites and services, or other features that constitute an integral part of the Software and ICQ Services; (4) connect, use, attempt to connect or use in any way the ICQ Services, for any commercial purpose and any other purpose that is not for your private personal use in good faith and as explicitly offered on the ICQ Web site; and (5) incorporate, integrate or otherwise include the software or any portion thereof (including the ICQ communications protocols) into any software, program or product that communicates, accesses, or otherwise connects with the ICQ Service or any other instant messaging, Internet, or online service. "

"You agree not to (1) create or use software that is not provided by ICQ, America Online, Inc., or its affiliates, to enter your ICQ number and password, or to use the ICQ services without expressly Approval from ICQ; (2) Extract, reverse engineer, decompile, disassemble, alter, duplicate, copy, create derivative works from, distribute or otherwise use the software, the ICQ communications protocol, or any other available derived information from the ICQ Services or to provide extracted information or parts thereof; (3) block, deactivate or in any other way influence advertising, advertising banner windows, links to other pages or services or other functions that are considered an integral part of the software and ICQ services; (4) to connect, use, attempt to connect or use the ICQ services in any way for commercial purposes or any intentions that do not correspond to private, personal use with good intent or not explicitly permitted by the ICQ website become; and (5) software or parts thereof (as well as the ICQ communication protocols) in other software, programs or products that communicate, control or in any other way connect with the ICQ services or any other instant messaging, Internet or online service to integrate, incorporate or otherwise incorporate. "

The reverse engineering and re-implementation is contrary to the above sections of the End User License Agreement under the German copyright § 69e allowed. The use of the resulting software in connection with the services of America Online / ICQ Inc. still contradicts the end user license agreement, if this has not been explicitly licensed by ICQ Inc./AOL. At the moment only AIM, ABV-ICQ, Atlas-ICQ, Bigmir-ICQ, ICQ, ICQ2GO, ProSieben-ICQ, Rambler-ICQ and Sat1-ICQ are officially licensed or officially modified clients. According to the license agreement, others may not be used with the ICQ services.

While the use of alternative clients did not comply with the license conditions, it was widespread - in particular, it was possible for users to only have to use and install one (alternative) client when using different messengers. However, this is no longer possible since the end of 2018 / beginning of 2019.


In February 2008, a security vulnerability in ICQ 6 Build 6043 became known that savvy users could exploit to execute arbitrary malicious code. It was closed in mid-March with a forced update from ICQ6. ICQ6's anti-spam protection now blocks potential malicious code that exploited this vulnerability.

Lack of transparency

The inability to view the source code of ICQ is seen as problematic and as a risk to the security, anonymity and privacy of users. ICQ shares this problem with almost all other instant messaging networks. In connection with the restrictive conditions of use with regard to alternative clients, the centralized architecture and the restricted protocol, this also means that ICQ participants are unconditionally dependent on Mirabilis.

Missing encryption

ICQ only offers a scrambling of the transmitted data, so the content of the communication is visible to every middleman. Some alternative clients (see above) offer encryption methods - mostly via plug-ins . Encryption is often only possible if both communication partners use the same client with the same plug-in. Exceptions are off-the-record messaging , which is now available for various clients, and SSL encryption between climm and Licq .

Data storage

An internal document published on "cryptome.org" shows that AOL stored the ICQ login data for up to 90 days.

"ICQ usage generates IP connection logs which are retained for up to 90 days."

Alternatives to the ICQ client

In addition to the official ICQ client, there are also compatible clients from third-party manufacturers. Most of them are open source software and support other protocols besides the ICQ protocol such as B. AIM, IRC, XMPP, MSN. However, ICQ Inc.'s Terms of Use explicitly prohibit the creation and use of alternative clients to interact with the ICQ service.

Individual evidence

  1. ^ A b Peter-Michael Ziegler: ICQ sold to Russia. heise online, April 28, 2010, accessed on November 22, 2010 .
  2. a b BUSINESS WIRE: Digital Sky Technologies (DST) Changes Name to Mail.ru Group. (No longer available online.) September 16, 2010, archived from the original on April 19, 2011 ; accessed on November 22, 2010 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.themenportal.de
  3. Tomorrow, 4/2006, p. 47
  4. a b c http://www.hardwareluxx.de/index.php/news/software/anendungprogramme/32166-erstmals-seit-jahren-instant-messenger-icq-waechst-wieder.html
  5. ^ Digital Sky Technologies to Acquire AOL's ICQ Instant Messaging Service. AOL , April 28, 2010, accessed May 8, 2010 .
  6. ICQ goes on the app offensive ( memento of the original from April 14, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , t3n, April 4, 2012. Retrieved April 17, 2012. @1@ 2Template: Webachiv / IABot / t3n.de
  7. The veteran of chat messengers is back , futurezone, March 21, 2016. Accessed July 30, 2016.
  8. DrWindows.de: ICQ: Support for older versions and unofficial clients will probably end - Update 1 ›Dr. Windows. Accessed on December 26, 2018 (German).
  9. ICQ.com: ICQ New - stay connected. Retrieved April 7, 2020 .
  10. Telecompaper: Mail.ru relaunches ICQ messenger. Retrieved April 7, 2020 .
  11. ^ ICQ system. ICQ, accessed on November 22, 2010 (ICQ profile of the ICQ System bot # 12111).
  12. All-clear: Don't be afraid of ICQ contact no. 12111. In: WinFuture. June 23, 2008, accessed November 22, 2010 .
  13. Москва Кремль. ICQ, accessed on May 8, 2018 (ICQ profile Москва Кремль # 10000).
  14. ^ ICQ system. ICQ, accessed November 22, 2010 (ICQ profile of the ICQ System bot # 10111).
  15. ICQ for Blackberry. (No longer available online.) Archived from the original on January 6, 2009 ; Retrieved November 22, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / blackberry.com
  16. ICQ for Linux. Retrieved May 27, 2011 .
  17. Overview: Open Xtraz Gallery
  18. Connection to ICQ failed ( Memento of the original from July 17, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. on archive link ( memento of the original from March 11, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , May 28, 2008  @1@ 2Template: Webachiv / IABot / www.virtualcoffeehouse.net @1@ 2Template: Webachiv / IABot / www.virtualcoffeehouse.net
  19. Is AOL opening up to Jabber? [Update]. heise online, January 18, 2008, accessed on November 22, 2010 .
  20. ^ ICQ Terms Of Service - Acceptable Use Policy on the ICQ homepage, June 7, 2000
  21. ICQ Privacy Policy on the ICQ homepage, April 30, 2006
  22. See also the question "Read along at ICQ?" In the "Readers' Forum" of the c't, edition 17/06 (page 11, left column (bottom))
  23. ICQ Terms Of Service - End User License Agreement on the ICQ homepage, April 5, 2006
  24. Instant Messaging: ICQ blocks alternative messenger clients - Golem.de. Retrieved on April 25, 2019 (German).
  25. Critical hole in Instant Messenger ICQ
  26. http://cryptome.org/isp-spy/aol-spy.pdf

Web links

Commons : ICQ  - collection of images, videos and audio files
Wiktionary: ICQ  - explanations of meanings, word origins, synonyms, translations