Mastodon is free and open-source software for running self-hosted social networking

services. It has microblogging features similar to Twitter, which are offered by a large

number of independently run nodes, known as instances or servers, each with its

own code of conduct, terms of service, privacy policy, privacy options, and content

moderation policies.

Each user is a member of a specific Mastodon server that can interact seamlessly

with users in any other server. This is intended to give users the flexibility to select a

server whose policies they prefer but keep access to a larger federated social

network. Mastodon is powered by the ActivityPub protocol, making it part of the

Fediverse ensemble of services such as Lemmy, Pixelfed, Friendica, PeerTube, and

Threads.

Mastodon was created by Eugen Rochko and announced on Hacker News in

October 2016.[9] It gained significant adoption in 2022 in the wake of Twitter’s

acquisition by Elon Musk. The project is maintained by the German non-profit Mastodon gGmbH. Mastodon

development is crowdfunded, and the code does not support advertisements.

Functionality and features

Mastodon servers run social networking software that is capable of communicating

using W3C’s ActivityPub standard, which has been implemented since version

1.6.[14] A Mastodon user can therefore interact with users on any other server in the

Fediverse that supports ActivityPub.

Since version 2.9.0, Mastodon has offered a single-column mode for new users by

default.[15] In advanced mode, Mastodon approximates the microblogging user

experience of TweetDeck. Users post short-form status messages, historically known

as “toots”,[16] for others to see. On a standard Mastodon instance, these messages

can include up to 500 text-based characters, greater than Twitter’s 280-character

limit. Some instances support even longer messages.

Users join a specific Mastodon server, rather than a single centralized website or

application. The servers are connected as nodes in a network, and each server can

administer 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, ethnicity, or

country.

Mastodon includes several 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

hidden main body of the message to reveal it. 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.

Here is a link for update: https://joinmastodon.org/