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Simple Slack API

This library allows an application to connect to Slack to receive and send messages from any channel as if it were a slack client.

The main purpose of this library is to build Slack bots able to react to channel events without having to configure any web hook.

With this library you should be able to connect to Slack and to send some messages in less than 20 lines (no one-liners).


You can add this library as a dependency to your Maven or Gradle project through JitPack.

Released versions are also availables on the maven central repository :

  • group id: com.ullink.slack
  • artifact id: simpleslackapi

How to use it ?

You can find some samples of the most common use cases in the samples folder.

Sample code

SlackSession session = SlackSessionFactory.createWebSocketSlackSession("slack-bot-auth-token");
SlackChannel channel = session.findChannelByName("general"); //make sure bot is a member of the channel.
session.sendMessage(channel, "hi im a bot" );


Supported Slack commands

All these commands can be sent through the library provided your bot has the rights to (IE : the bot has to be a member of the group or the channel to post some messages on it)

  • Post a message on a channel / private group / user
  • Post a typing indicator on a channel
  • Update a message
  • Delete a message
  • Join a channel
  • Leave a channel / a private group
  • Invite to a channel / a private group
  • Archive a channel
  • Open a direct message channel (since v0.5.0)
  • Open a multiparty direct message channel (since v0.5.0)
  • Get the presence status of a user
  • Add a reaction emoji to a message
  • Fetch the channel history (since v0.5.0) (needs full user credentials)
  • Invite a user to Slack (since v0.5.0)

On top of these built-in features, it is now possible to send not yet implemented API calls by using the postGenericSlackCommand method :

postGenericSlackCommand(Map<String, String> params, String command);

Supported Slack events

All these events can be listen provided your bot has the rights to (IE : the bot has to be a member of the group or a channel to gets the message events related to it)

  • message posted event
  • message deleted event
  • message updated event
  • channel created event
  • channel / private group deleted event
  • channel / private group archived event
  • channel / private group unarchived event
  • channel / private group renamed event
  • channel / private group joined event
  • reaction added to message event (since v0.5.0)
  • reaction removed from message event (since v0.5.0)
  • team joined event


From version 1.4.0 upward, channel members are not loaded in memory anymore in order for the api to start up faster. This should have no impact on the current behavior.


Many thanks to everyone who has contributed to this library :

  • Christian Sprecher
  • Jan Vidar Krey
  • David Seebacher
  • Wouter Vernaillen
  • Claudio Comandini
  • Maxim Gurkin
  • Ole Kozaczenko
  • Georges Gomes
  • François Valdy
  • Harry Fox
  • Logan Clément
  • Rhys Kenwell
  • Aman Gupta
  • Miklos Sagi
  • Nathalie Mahe
  • Sebastien Lelouvier
  • Nicolas Haquet

(Let me know if I forgot someone, I'll fix that ASAP ;) )


This library is licensed under the Creative Commons CC0 1.0 Universal license with no warranty (expressed or implied) for any purpose.