[10] Not long after, it quickly gained popularity and became the dominant platform in the fediverse and overtaking the previous leader, GNU social.

[19] Mastodon servers run social networking software that is capable of communicating using W3C's ActivityPub standard, which has been implemented since version 1.6.

On a standard Mastodon instance, these messages can include up to 500 text-based characters, greater than Twitter's 280-character limit.

Users can communicate across connected Mastodon servers with usernames similar in format to full email addresses.

[25][26] In early 2017, journalists like Sarah Jeong[27] distinguished Mastodon from Twitter for its approach to combating harassment.

By posting toots hashtagged with #fediblock, some instance administrators and users alert others of issues requiring moderation.

However, services utilizing the ActivityPub protocol exist which allow for searching all posts on all instances as long as users opt-in.

[33] For similar reasons, only hashtags can appear in a Mastodon instance's trending topics, not arbitrary popular words.

[37] Mastodon 2.6 was released in October 2018, introducing the possibilities of verified profiles and live, in-stream link previews for images and videos.

[39] The ability for users to create and vote in polls, as well as a new invitation system to manage registrations was integrated in April 2019.

It included a redesigned audio player with custom thumbnails and the ability to add personal notes to one's profile.

[25] The API is open for anyone to utilize, allowing clients to be built for any operating system that can connect to the internet.

[52] While Mastodon was first released in October 2016, the service began to expand in late March and early April 2017.

[27][57][58][59] Another spike in popularity came in March through April 2018, due to the concerns about user privacy raised by the #deletefacebook effort.

[85][86] Musk stated the following day that banning users for posting Mastodon links had been a mistake.

[90] In July 2023, Mastodon’s founder, Eugen Rochko, stated that monthly active users were increasing again, surpassing the 2-million mark.

[91] A study posted to arXiv in November 2023, showed that following Elon Musk's acquisition of Twitter and subsequent changes that ensued, there was a significant migration of users to alternative platforms.

[93] As a result of its open source nature and ability to be deployed without restriction, various organizations, companies and governments have started their own Mastodon instances.

[101][102] In April 2019, computer manufacturer Purism released a fork of Mastodon named Librem Social.

[106] 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".

[107] Gab later removed federation with ActivityPub due to various perceived technical issues and plans to build its own protocol.

Tooter is an Indian social networking product launched in September 2020 that uses the Mastodon source code, initially without releasing its modifications.

Eugen Rochko sent a formal letter to Truth Social's chief legal officer on 26 October 2021.

[113][114] In December 2022, the Mozilla Foundation launched a Mastodon instance under mozilla.social,[115] initially with closed registrations before opening it up as a private beta.

Configuration errors and security bugs in server implementation has already led to user data being scraped or modified by attackers.

It is worth noting that Mastodon also collects considerably less personal data, compared to other social media platforms, which makes it a lower-value target and reduces potential damage.

[118] The creator of Mastodon, Eugen Rochko, argues[citation needed] that these issues do not set it apart from other software products that can be hosted by non-professionals.