A bot user is a special kind of free user account. They're optimized for writing bots that connect to Slack using our Real Time Messaging API.
Connecting your bot to Slack in this way allows fine grained control over which channels your bot is in. You can even invite bots to private groups or interact with them using direct messages.
Like our other APIs and integrations bot users are free. Unlike regular users the actions they can perform are limited slightly. For teams on a lite plan each bot user counts as a seperate integration.
To write a bot, start by creating a new bot user integration. You'll need to pick a username for your new bot. Then, once the integration is added, you'll be given an API token.
If you're using an existing library (such as node-slack-client) then this API token should be all you need to get started.
If you're writing your own library from scratch, you'll need to write code to make authenticated API calls. Then you can write code to consume our Real Time Messaging API. And then you can start working on the interesting functionality of your bot.
In addition to the difference in pricing, there are a few technical differences between bot users and other Slack accounts.
Bot users do not have a password, so cannot be used to log on to slack.com or our clients. Account management can be done through the integration page for the bot user.
Bot users do not follow the usual rules for automatically being marked as away when inactive. In most cases you want a bot to show as "active" and ready to respond, even if it hasn't posted a message in a while. If you'd like a bot to show up as "away" you can use the users.setPresence API method.
Bot users can also only call a subset of our API methods. Any method that
cannot be used by a bot user will return a user_is_bot error, which will be
documented as an error in the method documentation. The full list of methods
that can be used by bot users is:
{METHOD_LIST}
You can tell if a user object returned by our API is a bot by
checking the is_bot property.