Pump.io

pump.io (pronounced "pump eye-oh") is a general-purpose activity stream engine that can be used as a federated social networking protocol which "does most of what people want from a social network". Started by Evan Prodromou, it is a follow-up to GNU Social (formerly StatusNet), and is designed to be more lightweight and usable for general data instead of just microblogging. The largest StatusNet instance at the time, Identi.ca, which was the largest StatusNet service and was run by Prodromou, switched to pump.io in June 2013.

As a distributed social network, pump.io is not tied to a single site. Users across servers can subscribe to each other, and if one or more individual nodes go offline the rest of the network remains intact.

The protocol was later used as a template for the creation and standardization of the ActivityPub standard, and development of pump.io has since been discontinued, with the latest version of the engine being released in 2020 and further development of the codebase ending in 2022.

Technology
Designed to be much more lightweight and efficient than its StatusNet predecessor, Pump.io is written in Node.js and uses Activity Streams as the format for commands and to transfer data via a simple REST inbox API.

Pump.io requires:
 * node.js
 * npm
 * a database server (typically NoSQL databases such as MongoDB or Redis, though there are other options through the database abstraction layer called Databank)
 * GraphicsMagick with the `gm` command

Pump.io can run easily on low-resource hardware (such as a Raspberry Pi or BeagleBone Black). It can be used via the Web UI, or other clients via the API.

Standardization
The W3C Federated Social Web Working Group, launched in July 2014, has produced the ActivityPub standard, based on the protocols used in pump.io as a likely successor to OStatus. It was officially published as a Recommendation on 23 January 2018. The protocol has since gone on to become the main standard used in the fediverse.