|Initial release||16 March 2016|
3.4.1 / June 3, 2021
|Platform||World Wide Web, iOS, Android, Linux, BSD, Sailfish OS, macOS, Microsoft Windows|
|Available in||69 languages|
Mastodon is free and open-source software for running self-hosted social networking services. It has microblogging features similar to the Twitter service, which are offered by a large number of independently run Mastodon nodes (known as "instances"), each with its own code of conduct, terms of service, privacy options, and moderation policies.
Each user is a member of a specific Mastodon instance, which can interoperate as a federated social network, allowing users on different nodes to interact with each other. This is intended to give users the flexibility to select a server whose policies they prefer, but keep access to a larger social network. Mastodon is also part of the Fediverse ensemble of server platforms, which use shared protocols allowing users to also interact with users on other compatible platforms, such as PeerTube and Friendica.
Functionality and features
Mastodon servers run social networking software that is capable of communicating using the ActivityPub standard, which has been implemented since version 1.6. A Mastodon user can therefore interact with users on any other server in the Fediverse that supports ActivityPub.
Since version 2.9.0 Mastodon offers a single column mode for new users by default. In advanced mode Mastodon approximates the microblogging user experience of TweetDeck. Users post short-form status messages for others to see. On a standard Mastodon instance, these messages can include up to 500 text-based characters, an extension of Twitter's 280 character limit, although numerous Mastodon servers have forked the source code to allow a larger character limit. Posts are called "toots" instead of "tweets", as is the case on Twitter.
Users join a specific Mastodon server, rather than a single website or application. The servers are connected as nodes in a network, and each server can administrate its own rules, account privileges, and whether to share messages to and from other servers. Many servers have a theme based on a specific interest. It is also common for servers to be based around a particular locality, region, or country.
Mastodon includes a number of specific privacy features. Each message has a variety of privacy options available, and users can choose whether the message is public or private. Public messages display on a global feed, known as a timeline, and private messages are only shared on the timelines of the user's followers. Messages can also be marked as unlisted from timelines or direct between users. Users can also mark their accounts as completely private. In the timeline, messages can display with an optional "content warning" feature, which requires readers to click on the content to reveal the rest of the message. Mastodon servers have used this feature to hide spoilers, trigger warnings, and not safe for work (NSFW) content, though some accounts use the feature to hide links and thoughts others might not want to read.
Mastodon aggregates messages in local and federated timelines in real-time. The local timeline shows messages from users on a singular server, while the federated timeline shows messages across all participating Mastodon servers. Users can communicate across connected Mastodon servers with usernames similar in format to full email addresses.
In early 2017, journalists like Sarah Jeong distinguished Mastodon from Twitter for its approach to combating harassment, one of Twitter's largest issues.[dubious ] Mastodon uses community-based moderation, in which each server can limit, or filter out undesirable types of content. For example, mastodon.social and several other servers ban content that is illegal in Germany or France, including Nazi symbolism, Holocaust denial and discrimination. Servers can also choose to limit, or filter out messages with disparaging content. Mastodon's founder Eugen Rochko believes that small, closely related communities deal with unwanted behaviour more effectively than a large company's small safety team. Users can also block and report others to administrators, much like on Twitter.
In September 2018, with the release of version 2.5 with redesigned public profile pages, Mastodon marked its 100th release. Then, at the end of October, Mastodon 2.6 came out, introducing the possibilities of verified profiles and live, in-stream link previews for images and videos. Since January 2019, it is possible to search for multiple hashtags at once, instead of searching for just a single hashtag, as was the case before the release of version 2.7. Version 2.7 also has more robust moderation capabilities for server administrators and moderators, while accessibility, such as contrast for users with sight issues, has also been improved. The ability for users to create and vote in polls, as well as a new invitation system to manage registrations have been integrated in April 2019. Since the release of Mastodon 2.8.1 in May 2019, images with content warnings are, by default, blurred instead of completely hidden. The most significant addition to Mastodon's functionality in June 2019 has been an optional single-column view in version 2.9. This view is now displayed by default to all new users, although it can be changed to the original column-based view in Mastodon's preferences.
In August of 2020, Mastodon 3.2 was released. It included a redesigned audio player with custom thumbnails and the ability to add personal notes to one's profile.
This section needs expansion with: more details on technical information. You can help by adding to it. (November 2018)
Mastodon is written as a free, web-based software for federated microblogging, which anybody can contribute code to, and which anyone can run on their own server infrastructure, if they wish, or join servers run by other people within the fediverse network. Its server-side technology is powered by Ruby on Rails and Node.js, and its front end is written in React.js and Redux. The database software is PostgreSQL. The service is interoperable with the decentralized social networks and platforms which use the ActivityPub protocol between each other. Since version 3.0, Mastodon dropped previous support for OStatus. 
Client apps for mobile devices, desktop computers, and web browsers interacting with the Mastodon API have been released for a range of operating systems, including Windows, macOS, Linux, Android, and iOS.
While Mastodon was first released in October 2016, the service began to expand in late March and early April 2017. The Verge wrote that the community at this time was small and that it had yet to attract the personalities that keep users at Twitter. The global use has risen from 766,500 users as of 1 August 2017, to 1 million users on 1 December 2017. In November 2017 artists, writers and entrepreneurs such as Chuck Wendig, John Scalzi, Melanie Gillman and later John O'Nolan joined in. Another spike in popularity came in March, through April 2018, due to the concerns about user privacy raised by the #deletefacebook effort.
Mastodon, along with a number of other alternative social media sites, saw a large uptick in membership, gaining thousands of new members in the period of a few hours compared to dozens in days prior, following Tumblr's announcement of intent in early December 2018 to ban all sensitive content from their site.
Gab, a controversial social network with a far-right user base, changed its software platform to a fork of Mastodon and became the largest Mastodon node in July 2019. Gab's adoption of Mastodon allowed Gab to be accessed from third-party Mastodon applications, although four of them blocked Gab shortly after the change. In response, Mastodon's main contributors stated in their blog that they were "completely opposed to Gab’s project and philosophy", and criticized Gab for attempting "to monetize and platform racist content while hiding behind the banner of free speech" and for "paywalling basic features that are freely available on Mastodon".
- Comparison of microblogging services
- Comparison of software and protocols for distributed social networking
- Diaspora (social network)
- The Fediverse
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