Free cross-platform messenging service
|Developer(s)||Telegram FZ LLC|
Telegram Messenger Inc.
|Initial release||14 August 2013; 7 years ago (2013-08-14)|
|Android, Original||7.0.1 / 22 August 2020; 23 days ago (2020-08-22)|
|Android, Telegram X||0.22.8.1361 / 15 May 2020; 3 months ago (2020-05-15)|
|iOS||7.0 / 14 August 2020; 31 days ago (2020-08-14)|
|Windows, macOS, Linux||2.3.2 / 23 August 2020; 22 days ago (2020-08-23)|
|Windows (Microsoft Store)||2.3.2 / 23 August 2020; 22 days ago (2020-08-23)|
|macOS (Mac App Store version)||7.0 / 19 August 2020; 26 days ago (2020-08-19)|
|Android, original||5.12.0 (17400) / 6 October 2019; 11 months ago (2019-10-06)|
|iOS||5.12 (15550) / 6 October 2019; 11 months ago (2019-10-06)|
|Windows, macOS, Linux||1.8.5 / 5 September 2019; 12 months ago (2019-09-05)|
|macOS (Mac App Store version)||5.8 (182623) / 18 September 2019; 11 months ago (2019-09-18)|
|Platform||Android, iOS, Windows Phone, Windows NT, macOS, GNU/Linux, Web platform|
|Available in||14 languages|
|License||GNU GPLv2 or GPLv3 (clients), proprietary (server)|
|Alexa rank|| 188 (April 2020[update])|
Telegram is a cloud-based instant messaging, videotelephony and voice over IP service with end-to-end encryption for secret chat only. Telegram client apps are available for Android, iOS, Windows Phone, Windows, macOS and GNU/Linux and originated in Russia in 2013. Users can send messages and exchange photos, videos, stickers, audio and files of any type.
Telegram's client-side code is free software, whereas its server-side code is closed-source and proprietary. The service also provides APIs to independent developers. As of April 2020, Telegram had 400 million monthly active users. An announcement at that time included a promise to implement secure group video calls later in 2020.
The default messages and media use client-server encryption during transit. This data is also encrypted at rest, but can be accessed by Telegram developers, who hold the encryption keys. In addition Telegram provides end-to-end encrypted calls and optional end-to-end encrypted "secret" chats between two online users on smartphone clients. However, the desktop clients (excluding macOS client) do not feature end-to-end encryption, nor is end-to-end encryption available for groups, supergroups, or channels. Telegram has defended the lack of ubiquitous end-to-end encryption by claiming the online-backups that do not use client-side encryption are "the most secure solution currently possible," despite several other chat services such as Signal, Matrix, and WhatsApp offering end-to-end encryption on all platforms.
Telegram was launched in 2013 by the brothers Nikolai and Pavel Durov. Previously, the pair founded the Russian social network VK, which they left when it was taken over by the Mail.ru Group. Nikolai Durov created the MTProto protocol that is the basis for the messenger, while Pavel provided financial support and infrastructure through his Digital Fortress fund with partner Axel Neff joining as a second co-founder. The Company and the App was started in Russia and shifted to Germany. Telegram Messenger LLP states that its end goal is not to bring profit, but it is not currently structured as a non-profit organization.
Telegram is registered as both an English LLP and an American LLC. It does not disclose where it rents offices or which legal entities it uses to rent them, citing the need to "shelter the team from unnecessary influence" and protect users from governmental data requests. Pavel Durov has said that the service was headquartered in Berlin, Germany, between 2014 and early 2015, but moved to different jurisdictions after failing to obtain residence permits for everyone on the team. Durov left Russia and is said to be moving from country to country with a small group of computer programmers consisting of 15 core members. According to press reports, Telegram had employees in St. Petersburg. The Telegram team is currently based in Dubai.
In October 2013, Telegram had 100,000 daily active users. On 24 March 2014, Telegram announced that it had reached 35 million monthly users and 15 million daily active users. In October 2014, South Korean governmental surveillance plans drove many of its citizens to switch to Telegram. In December 2014, Telegram announced that it had 50 million active users, generating 1 billion daily messages, and that it had 1 million new users signing up on its service every week, traffic doubled in five months with 2 billion daily messages. In September 2015, an announcement stated that the app had 60 million active users and delivered 12 billion daily messages.
In February 2016, Telegram announced that it had 100 million monthly active users, with 350,000 new users signing up every day, delivering 15 billion messages daily. In December 2017, Telegram reached 180 million monthly active users. In March 2018, Telegram reached 200 million monthly active users. On 14 March 2019, Pavel Durov claimed that "3 million new users signed up for Telegram within the last 24 hours." Durov did not specify what prompted this flood of new sign-ups, but the period matched a prolonged technical outage experienced by Facebook and its family of apps, including Instagram. On 24 April 2020 Telegram announced it had reached 400 million monthly active users.
According to the U.S. Securities and Exchange Commission, the number of monthly Telegram users as of October 2019 is 300 million people worldwide.
If This Then That (IFTTT) Integration
People can use Internet Of Things (IoT) services using two-ways interacion for IFTTT implemented within Telegram.
Instant View 2.0
Instant View is a way to view web articles with zero pageload time. With Instant View, Telegram users can enjoy articles from any mass media or blogs in a uniform and easily readable way. Instant View pages support text and media of any type and work great even if the original website was not optimized for mobile devices.
On top of this, Instant View pages are extremely lightweight and are cached on the Telegram servers, so they load instantly on pretty much any connection — hence the name. 
Telegra.ph is a publishing tool that lets you create richly formatted posts with photos and all sorts of embedded media.
Telegram accounts are tied to telephone numbers and are verified by SMS. Users can add multiple devices to their account and receive messages on each one. Connected devices can be removed individually or all at once. The associated number can be changed at any time and when doing so, the user's contacts will receive the new number automatically. In addition, a user can set up an alias that allows them to send and receive messages without exposing their phone number. Telegram accounts can be deleted at any time and they are deleted automatically after six months of inactivity by default, which can optionally be changed to 1 month and 12 months. Users can replace exact "last seen" timestamps with broader messages such as "last seen recently".
The default method of authentication that Telegram uses for logins is SMS-based single-factor authentication. All that is needed in order to log into an account and gain access to that user's cloud-based messages is a one-time passcode that is sent via SMS to the user's phone number. These login SMS messages are known to have been intercepted in Iran, Russia and Germany, possibly in coordination with phone companies. Pavel Durov has said that Telegram users in "troubled countries" should enable two-factor authentication by creating passwords, which Telegram allows, but does not require.
Telegram's local message database is not encrypted by default. Some Telegram clients allow users to encrypt the local message database by setting a passphrase.
In June 2015, Telegram launched a platform for third-party developers to create bots. Bots are Telegram accounts operated by programs. They can respond to messages or mentions, can be invited into groups and can be integrated into other programs. It also accepts online payments with credit cards and Apple Pay. Dutch website Tweakers reported that an invited bot can potentially read all group messages when the bot controller changes the access settings silently at a later point in time. Telegram pointed out that it considered implementing a feature that would announce such a status change within the relevant group. Also, there are inline bots, which can be used from any chat screen. In order to activate an inline bot, user needs to type in the message field a bot's username and query. The bot then will offer its content. User can choose from that content and send it within a chat.
Payment API for bots
Bots can handle transactions provided by Paymentwall,Yandex.Money, Stripe, Ravepay, Razorpay and QiWi for different countries.
Bot-powered gaming platform
Telegram games can be anything from simple arcades and puzzles to multiplayer 3D-shooters and real-time strategy games. The underlying technology is HTML5, so games are loaded on-demand as needed, just like ordinary webpages. Games will work on iPhones 4 and newer and on Android 4.4 devices and newer.
In September 2015, Telegram added channels. Channels are a form of one-way messaging where admins are able to post messages but other users are not. Any user is able to create and subscribe to channels. Channels can be created for broadcasting messages to an unlimited number of subscribers. Channels can be publicly available with an alias and a permanent URL so anyone can join. Users who join a channel can see the entire message history. Users can join and leave channels at any time. Depending on a channel's settings, messages may be signed with the channel's name or with the username of the admin who posted them. Non-admin users are unable to see other users who've subscribed to the channel. Furthermore, users can mute a channel, meaning that the user will still receive messages, but won't be notified. Admins can give permission to post comments on the Telegram channel with help of bots. The admin of the channel can obtain general data about the channel. Each message has its own view counter, showing how many users have seen this message, this includes views from forwarded messages. As of May 2019, the creator of a channel can add a discussion group, a separate group where messages in the channel are automatically posted for subscribers to communicate.
In December 2019, Bloomberg moved their messenger-based newsletter service from WhatsApp to Telegram after the former banned bulk and automated messaging. The news service is attempting to grow its audience outside the U.S.
In the latest update of May 2020 Telegram has added custom folders in which one can filter out and put personal chats, groups, channels, contacts, non-contacts, and selected chats/groups/channels in different and customized folders.
Telegram has more than 20,000 stickers. The stickers are cloud-based, high-resolution images intended to provide more expressive emoji. When typing in an emoji, the user is offered to send the respective sticker instead. Stickers come in collections called "sets", and multiple stickers can be offered for one emoji. Telegram comes with one default sticker set, but users can install additional sticker sets provided by third-party contributors. Sticker sets installed from one client become automatically available to all other clients. Sticker images use WebP file format, which is better optimized to be transmitted over internet.
Drafts are unfinished messages synced across user devices. One can start typing a message on one device and continue on another. The draft will persist in editing area on any device until it is sent or removed.
Messages can also be sent with client-to-client encryption in so-called secret chats. These messages are encrypted with the service's MTProto protocol. Unlike Telegram's cloud-based messages, messages sent within a secret chat can be accessed only on the device upon which the secret chat was initiated and the device upon which the secret chat was accepted; they cannot be accessed on other devices. Messages sent within secret chats can, in principle, be deleted at any time and can optionally self-destruct.
Secret chats have to be initiated and accepted by an invitation, upon which the encryption keys for the session are exchanged. Users in a secret chat can verify that no man-in-the-middle attack has occurred by comparing pictures that visualize their public key fingerprints.
According to Telegram, secret chats have supported perfect forward secrecy since December 2014. Encryption keys are periodically changed after a key has been used more than 100 times or has been in use for more than a week. Old encryption keys are destroyed.
Windows and GNU/Linux users are still not able to use secret chats using the official Telegram Desktop app while the official macOS-only client supports them.
Secret chats are not available for groups or channels.
Free video and voice calls
In the end of March 2017, Telegram introduced its own voice calls. The calls are built upon the end-to-end encryption. Connection is established as peer-to-peer whenever possible, otherwise the closest server to the client is used. According to Telegram, there is a neural network working to learn various technical parameters about a call to provide better quality of the service for future uses. After a brief initial trial in Western Europe, voice calls are now available for use in most countries. On 15 August 2020, Telegram added video calling with end-to-end encryption like Signal and WhatsApp, which Zoom does not have yet. Currently offering one-to-one video calls, Telegram has plans to introduce secure group video calls later in 2020. Picture-in-picture mode is also available so that users have the option to simultaneously use the other functions of the app while still remaining on the call and are even able to turn their video off. 
Telescope (video messages)
Since version 4.1, released in May 2017, Telegram offers a dedicated video hosting platform called Telescope. The round videos can be up to one minute long and autoplay. When posted in a public channel on Telegram, the videos are also uploaded to and viewable without an account. However, Telegram video messages and "Telescope" videos sent within non-public chats or groups are not published.
For either 15 minutes, one hour, or eight hours, Telegram users can share their live location in a chat since version 4.4 released in October 2017. If multiple users share their live location within a group, they are shown on an interactive map. Sharing the 'live location' can be stopped at any time.
In February 2018, Telegram launched their social login feature to its users, named as Telegram Login. It features a website widget that could be embedded into websites, allowing users to sign into a third party website with their Telegram account. The gateway sends users' Telegram name, username, and profile picture to the website owner, while users' phone number remains hidden. The gateway is integrated with a bot, which is linked with the developer's specific website domain.
People Nearby 2.0 and Groups Nearby
People Nearby 2.0 can help users meet new friends by turning on phone GPS location and opting-in in contacts and through Groups Nearby people can create a local group by adding location data to groups.
In July 2018, Telegram introduced their online authorisation and identity management system, Telegram Passport, for platforms that require real-life identification. It asks users to upload their own official documents such as passport, identity card, driver license, etc. When an online service requires such identification documents and verification, it forwards the information to the platform with the user's permission. Telegram stated that it does not have access to the data, while the platform will only share the information to the authorised recipient. However, the service was criticised for being vulnerable to online brute force attacks.
Polls are a feature of Telegram that are currently available on Android, iOS and the desktop applications. Polls have the option to be anonymous or visible. A user can enter multiple options into the poll. Quiz mode can also be enabled where a user can select the right answer for their poll and leave it to the group to guess. Quiz bots can also be added to track correct answers and even provide a global leaderboard.
Native file format support
The official Telegram clients support sending any file format extensions. Natively supported in their viewer/player in mobile and desktops versions of Telegram are the common media formats - JPEG, PNG, WebP for images and H.264 and HEVC in videos in MP4 container and MP3, Vorbis, Opus and AAC for audio.
Send when Online
Telegram adds the scheduled message feature that was launched in a previous update called "Send when Online". This feature will allow users to draft a message and automatically send it when the receiver comes online. The new feature can be found within the Schedule Message option.
A simplified illustration of the MTProto encryption scheme.
Telegram uses a symmetric encryption scheme called MTProto. The protocol was developed by Nikolai Durov and other developers at Telegram and is based on 256-bit symmetric AES encryption, 2048-bit RSA encryption and Diffie–Hellman key exchange.
Telegram Messenger LLP has servers in a number of countries throughout the world to improve the response time of their service. Telegram's server-side software is closed-source and proprietary. Pavel Durov has said that it would require a major architectural redesign of the server-side software to connect independent servers to the Telegram cloud.
For users who signed in from the European Economic Area (EEA) or United Kingdom, the General Data Protection Regulations (GDPR) are supported by storing data only on servers in the Netherlands, and designating a London based company as their responsible data controller.
Telegram has various client apps, some developed by Telegram Messenger LLP and some by the community. Most of them are free and open-source and released under the GNU General Public Licenceversion 2 or 3.
- No cloud backup option for secret chat
|Name||Platform(s)||Official||Source code license||Support for secret chats||Notes |
|Telegram||Android 2.3 or later||Yes||GPLv2 or later||Yes||Supports tablets and Android Wear smart watches. Support synchronisation between multiple devices. |
|Telegram Messenger||iOS 9.0 or later, watchOS 5.0 or later||Yes||GPLv2 or later||Yes||Launched in August 2013 for iPhone and iPod Touch and relaunched in July 2014 with support for iPad and Apple Watch.|
|Telegram X||Android||Yes||Proprietary||Yes||An alternative Telegram client written from scratch, with higher speed, slicker animations, themes and more efficient battery use. |
iOS version is written with Swift. Android version based on TDLib. The iOS version was discontinued, with its code merged with the main Telegram app.
|Telegram Messenger||Windows Phone||Yes||GPLv2 or later||Yes||Provide synchronization between all platforms |
|Telegram||Firefox OS||Yes||GPLv3||No||Based on Webogram. |
|Telegram Desktop||Windows, macOS, and GNU/Linux||Yes||GPLv3 with OpenSSL exception||No||Qt-based desktop client. The Windows client is a traditional desktop app published in three flavors: |
With installer, portable, Windows Store app.
|Telegram||macOS||Yes||GPLv2||Yes||Native macOS client. |
|Telegram||Google Chrome and Chrome OS||Yes||GPLv3||No||Based on Webogram, published on the Chrome Web Store. |
Telegram has public APIs with which developers can access the same functionality as Telegram's official apps to build their own messaging applications. In February 2015, creators of the unofficial Whatsapp+ client released the Telegram Plus app, later renamed to Plus Messenger, after their original project got a cease-and-desist order from WhatsApp. In September 2015, Samsung released a messaging application based on these APIs.
Telegram also offers an API that allows developers to create bots, which are accounts controlled by programs. In February 2016, Forbes launched an AI-powered news bot that pushes popular stories to subscribers and replies to search queries with relevant articles.TechCrunch launched a similar bot in March 2016. (Both of them are down)
Telegram's security model has received notable criticism by cryptography experts. They criticized the general security model of permanently storing all contacts, messages and media together with their decryption keys on its servers by default and by not enabling end-to-end encryption for messages by default.Pavel Durov has argued that this is because it helps to avoid third-party unsecure backups, and to allow users to access messages and files from any device. Cryptography experts have furthermore criticized Telegram's use of a custom-designed encryption protocol that has not been proven reliable and secure.
Cryptography experts have expressed both doubts and criticisms on Telegram's MTProto encryption scheme, saying that deploying home-brewed and unproven cryptography may render the encryption vulnerable to bugs that potentially undermine its security, due to a lack of scrutiny. It has also been suggested that Telegram did not employ developers with sufficient expertise or credibility in this field.
Critics have also disputed claims by Telegram that it is "more secure than mass market messengers like WhatsApp and Line", because WhatsApp applies end-to-end encryption to all of its traffic by default and uses the Signal Protocol, which has been "reviewed and endorsed by leading security experts", while Telegram does neither and insecurely stores all messages, media and contacts in their cloud. Since July 2016, Line has also applied end-to-end encryption to all of its messages by default.
The Electronic Frontier Foundation (EFF) listed Telegram on its "Secure Messaging Scorecard" in February 2015. Telegram's default chat function received a score of 4 out of 7 points on the scorecard. It received points for having communications encrypted in transit, having its code open to independent review, having the security design properly documented, and having completed a recent independent security audit. Telegram's default chat function missed points because the communications were not encrypted with keys the provider didn't have access to, users could not verify contacts' identities, and past messages were not secure if the encryption keys were stolen. Telegram's optional secret chat function, which provides end-to-end encryption, received a score of 7 out of 7 points on the scorecard. The EFF said that the results "should not be read as endorsements of individual tools or guarantees of their security", and that they were merely indications that the projects were "on the right track".
In December 2015, two researchers from Aarhus University published a report in which they demonstrated that MTProto does not achieve indistinguishability under chosen-ciphertext attack (IND-CCA) or authenticated encryption. The researchers stressed that the attack was of a theoretical nature and they "did not see any way of turning the attack into a full plaintext-recovery attack". Nevertheless, they said they saw "no reason why [Telegram] should use a less secure encryption scheme when more secure (and at least as efficient) solutions exist". The Telegram team responded that the flaw does not affect message security and that "a future patch would address the concern". Telegram 4.6, released in December 2017, supports MTProto 2.0, which now satisfied the conditions for IND-CCA.MTProto 2.0 is seen by qualified cryptographers as a vast improvement to Telegram's security.
In April 2016, accounts of several Russian opposition members were hijacked by intercepting the SMS messages used for login authorization. In response, Telegram recommended using the optional two-factor authentication feature. In May 2016, the Committee to Protect Journalists and Nate Cardozo, senior staff attorney at Electronic Frontier Foundation, recommended against using Telegram because of "its lack of end-to-end encryption [by default] and its use of non-standard MTProto encryption protocol, which has been publicly criticized by cryptography researchers, including Matthew Green".
In June 2017, Pavel Durov in an interview publicly claimed that U.S. intelligence agencies tried to bribe the company's developers to weaken Telegram's encryption or install a backdoor during their visit to the U.S. in 2016.
In 2018 Telegram sent a message to all Iranian users stating Telegram Talai and Hotgram unofficial clones are not secure.
Telegram promised since at least March 2014 that "all code will be released eventually", including all the various client applications (Android, iOS, desktop, etc.) and the server-side code. As of August 2020, Telegram still hasn't published their server-side source code.
On 9 June 2019, The Intercept released leaked Telegram messages exchanged between current Brazilian Minister of Justice and former judge Sérgio Moro and federal prosecutors. The hypothesis is that either mobile devices were hacked by SIM swap or computers invaded. The Telegram team tweeted that it was either because the user had malware or they were not using 2-step verification.
On 12 June 2019, Telegram confirmed that it suffered a denial-of-service attack which disrupted normal app functionality for approximately one hour. Pavel Durov tweeted that the IP addresses used in the attack mostly came from China.
In December 2019 media wrote about a numerous Telegram account takeovers of Russian businessmen that involved bypass of SMS second factor authentication. Takeover of Telegram account was also offered on dark web forums for $4000. Group-IB security company suggested SS7 mobile signalling protocol weaknesses, illegal usage of surveillance equipment or telecom insider attacks.
Telegram has organized two cryptography contests to challenge its own security. Third parties were asked to break the service's cryptography and disclose the information contained within a secret chat between two computer-controlled users. A reward of respectively US$200,000 and US$300,000 was offered. Both of these contests expired with no winners. Security researcher Moxie Marlinspike and commenters on Hacker News criticized the first contest for being rigged or framed in Telegram's favor and said that Telegram's statements on the value of these contests as proof of the cryptography's quality are misleading. This was because the cryptography contest could not be won even with completely broken algorithms such as MD2 (hash function) used as key stream extractor, and primives such as the Dual_EC_DRBG that is known to be backdoored.
Telegram was open and working in Iran without any VPN or other circumvention methods in May 2015. In August 2015, the Iranian Ministry of ICT asserted that Telegram had agreed to restrict some of its bots and sticker packs in Iran at the request of the Iranian government. According to an article published on Global Voices, these features were being used by Iranians to "share satirical comments about the Iranian government". The article also noted that "some users are concerned that Telegram's willingness to comply with Iranian government requests might mean future complicity with other Iranian government censorship, or even allow government access to Telegram's data on Iranian users". Telegram has stated that all Telegram chats are private territory and that they do not process any requests related to them. Only requests regarding public content (bots and sticker packs) will be processed. In May 2016, the Iranian government asked all messaging apps, including Telegram, to move all Iranian users' data to Iranian servers. On 20 April 2017, the Iranian government completely blocked Telegram's new voice calls, a service that allows individuals to make calls via secure, end-to-end encryption, and keep their conversations private.Mahmoud VaeziChief of Staff of the President of Iran said reason for blocking Telegram free voice calls is so Iranian corporations keep revenue from voice calls.
On 30 December 2017, during anti-government demonstrations across Iran, Telegram has shut down a channel of the Iranian opposition that published calls to use Molotov cocktails against the police, after receiving a complaint from the Iranian government. Pavel Durov explained that the reason for the blocking was a "no calls to violence" policy and confirmed that criticizing local authorities, challenging the status quo and engaging in political debate were seen as "OK" by the platform, while "promoting violence" was not. The opposition group promised to comply with Telegram rules and created a new channel which amassed 700,000 subscribers in less than 24 hours. On December, 31, the Iranian government announced that Telegram has been "temporarily restricted" in order to "ensure calm and security" after the company said it refused to shut down peaceful protesting channels.