Code Quality Rank: L5
Monthly Downloads: 1,533,959
Programming language: Ruby
License: MIT License
Tags: Third-party APIs     Projects    
Latest version: v2.4.0

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A simple wrapper to send notifications to Slack webhooks.

Build Status Code Climate Gem Version SemVer


require 'slack-notifier'

notifier = Slack::Notifier.new "WEBHOOK_URL"
notifier.ping "Hello World"
# => if your webhook is setup, will message "Hello World"
# => to the default channel you set in slack


Install the latest stable release:

$ gem install slack-notifier

Or with Bundler, add it to your Gemfile:

gem "slack-notifier"

Setting Defaults

On initialization you can set default payloads by calling defaults in an initialization block:

notifier = Slack::Notifier.new "WEBHOOK_URL" do
  defaults channel: "#default",
           username: "notifier"

notifier.ping "Hello default"
# => will message "Hello default"
# => to the "#default" channel as 'notifier'

To get the WEBHOOK_URL you need:

  1. go to https://slack.com/apps/A0F7XDUAZ-incoming-webhooks
  2. choose your team, press configure
  3. in configurations press add configuration
  4. choose channel, press "Add Incoming WebHooks integration"

You can also set defaults through an options hash:

notifier = Slack::Notifier.new "WEBHOOK_URL", channel: "#default",
                                              username: "notifier"

These defaults are over-ridable for any individual ping.

notifier.ping "Hello random", channel: "#random"
# => will ping the "#random" channel


Slack requires links to be formatted a certain way, so the default middlware stack of slack-notifier will look through your message and attempt to convert any html or markdown links to slack's format before posting.

Here's what it's doing under the covers:

message = "Hello world, [check](http://example.com) it <a href='http://example.com'>out</a>"
# => "Hello world, <http://example.com|check> it <http://example.com|out>"


Slack supports various different formatting options. For example, if you want to alert an entire channel you include <!channel> in your message

message = "<!channel> hey check this out"
notifier.ping message

#ends up posting "@channel hey check this out" in your Slack channel

You can see Slack's message documentation here


Since sequences starting with < have special meaning in Slack, you should use Slack::Notifier::Util::Escape.html if your messages may contain &, < or >.

link_text = Slack::Notifier::Util::Escape.html("User <[email protected]>")
message = "Write to [#{link_text}](mailto:[email protected])"
notifier.ping message


This plugin supports the Slack blocks format and block kit builder. This is useful for displaying buttons, dropdowns, and images.

blocks = [
    "type": "image",
    "title": {
      "type": "plain_text",
      "text": "image1",
      "emoji": true
    "image_url": "https://api.slack.com/img/blocks/bkb_template_images/onboardingComplex.jpg",
    "alt_text": "image1"
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "Hey there 👋 I'm TaskBot. I'm here to help you create and manage tasks in Slack.\nThere are two ways to quickly create tasks:"

notifier.post(blocks: blocks)

Additional parameters

Any key passed to the post method is posted to the webhook endpoint. Check out the Slack webhook documentation for the available parameters.

Setting an icon:

notifier.post text: "feeling spooky", icon_emoji: ":ghost:"
# or
notifier.post text: "feeling chimpy", icon_url: "http://static.mailchimp.com/web/favicon.png"

Adding attachments:

a_ok_note = {
  fallback: "Everything looks peachy",
  text: "Everything looks peachy",
  color: "good"
notifier.post text: "with an attachment", attachments: [a_ok_note]

HTTP options

With the default HTTP client, you can send along options to customize its behavior as :http_options params when you post or initialize the notifier.

notifier = Slack::Notifier.new 'WEBHOOK_URL', http_options: { open_timeout: 5 }
notifier.post text: "hello", http_options: { open_timeout: 10 }

Note: you should only send along options that Net::HTTP has as setters, otherwise the option will be ignored and show a warning.


:http_options can be used if you need to connect to Slack via an HTTP proxy. For example, to connect through a local squid proxy the following options would be used.

notifier = Slack::Notifier.new 'WEBHOOK_URL', http_options: {
                                                              proxy_address:  'localhost',
                                                              proxy_port:     3128,
                                                              proxy_from_env: false

Custom HTTP Client

There is a packaged default client wrapping Net::HTTP, but your HTTP needs might be a little different. In that case, you can pass in your own wrapper to handle sending the notifications. It just needs to respond to ::post with the arguments of the endpoint URI, and the payload pretty much the same as Net:HTTP.post_form.

A simple example:

module Client
  def self.post uri, params={}
    Net::HTTP.post_form uri, params

notifier = Slack::Notifier.new 'WEBHOOK_URL' do
  http_client Client

It's also encouraged for any custom HTTP implementations to accept the :http_options key in params.

Setting client per post

You can also set the http_client per-post if you need to special case certain pings.

notifier.post text: "hello", http_client: CustomClient

Setting a No-Op client

In development (or testing), you may want to watch the behavior of the notifier without posting to slack. This can be handled with a no-op client.

class NoOpHTTPClient
  def self.post uri, params={}
    # bonus, you could log or observe posted params here

notifier = Slack::Notifier.new 'WEBHOOK_URL' do
  http_client NoOpHTTPClient


By default slack-notifier ships with middleware to format links in the message & text field of attachments. You can configure the middleware a notifier will use on initialization:

notifier = Slack::Notifier.new "WEBHOOK_URL" do
  middleware format_message: { formats: [:html] }
# this example will *only* use the format_message middleware and only format :html links

notifier.post text: "Hello <a href='http://example.com'>world</a>! [visit this](http://example.com)"
# => will post "Hello <http://example.com|world>! [visit this](http://example.com)"

The middleware can be set with a their name, or by name and options. They will be triggered in order.

notifier = Slack::Notifier.new "WEBHOOK_URL" do
  middleware :format_message, :format_attachments
# will run format_message then format_attachments with default options

notifier = Slack::Notifier.new "WEBHOOK_URL" do
  middleware format_message: { formats: [:html] },
             format_attachments: { formats: [:markdown] }
# will run format_message w/ formats [:html] then format_attachments with formats [:markdown]

Available middleware:


This middleware takes the :text key of the payload and runs it through the Linkformatter. You can configure which link formats to look for with a :formats option. You can set [:html] (only html links), [:markdown] (only markdown links) or [:html, :markdown] (the default, will format both).


This middleware takes the :text key of any attachment and runs it through the Linkformatter. You can configure which link formats to look for with a :formats option. You can set [:html] (only html links), [:markdown] (only markdown links) or [:html, :markdown] (the default, will format both).


This simplifies the process of notifying users and rooms to messages. By adding an :at key to the payload w/ an array of symbols the appropriately formatted commands will be prepended to the message. It will accept a single name, or an array.

For example:

notifier.post text: "hello", at: :casper
# => "<@casper> hello"

notifier.post text: "hello", at: [:here, :waldo]
# => "<!here> <@waldo> hello"


If the channel argument of a payload is an array this splits the payload to be posted to each channel.

For example:

notifier.post text: "hello", channel: ["default", "all_the_things"]
# => will post "hello" to the default and all_the_things channel

To send a message directly to a user, their username no longer works. Instead you'll need to get the user's ID and set that as the channel.

At the time of writing, one way to get a user's ID is to:

  • go to their profile
  • click ... ("More actions")
  • click Copy Member ID

Writing your own Middleware

Middleware is fairly straightforward, it is any class that inherits from Slack::Notifier::PayloadMiddleware::Base and responds to #call. It will always be given the payload as a hash and should return the modified payload as a hash.

For example, lets say we want to replace words in every message, we could write a middleware like this:

class SwapWords < Slack::Notifier::PayloadMiddleware::Base
  middleware_name :swap_words # this is the key we use when setting
                              # the middleware stack for a notifier

  options pairs: ["hipchat" => "slack"] # the options takes a hash that will
                                        # serve as the default if not given any
                                        # when initialized

  def call payload={}
    return payload unless payload[:text] # noope if there is no message to work on

    # not efficient, but it's an example :)
    options[:pairs].each do |from, to|
      payload[:text] = payload[:text].gsub from, to

    payload # always return the payload from your middleware

notifier = Slack::Notifier.new "WEBHOOK_URL" do
  middleware :swap_words # setting our stack w/ just defaults
notifier.ping "hipchat is awesome!"
# => pings slack with "slack is awesome!"

notifier = Slack::Notifier.new "WEBHOOK_URL" do
  # here we set new options for the middleware
  middleware swap_words: { pairs: ["hipchat" => "slack",
                                   "awesome" => "really awesome"]}

notifier.ping "hipchat is awesome!"
# => pings slack with "slack is really awesome!"

If your middleware returns an array, that will split the message into multiple pings. An example for pinging multiple channels:

class MultiChannel < Slack::Notifier::PayloadMiddleware::Base
  middleware_name :channels

  def call payload={}
    return payload unless payload[:channel].respond_to?(:to_ary)

    payload[:channel].to_ary.map do |channel|
      pld = payload.dup
      pld[:channel] = channel


Since version 1.0 has been released, the aim is to follow Semantic Versioning as much as possible. However, it is encouraged to check the [changelog](changelog.md) when updating to see what changes have been made.

To summarize the reasoning for versioning:

Given a version number MAJOR.MINOR.PATCH, increment:

- MAJOR version when incompatible API changes are made
- MINOR version for adding functionality in a backwards-compatible manner or bug fixes that *may* change behavior
- PATCH version for make backwards-compatible bug fixes


$ rspec

There is also an integration test setup to just double check pinging across the supported rubies. To run:

  1. Copy the .env-example file to .env and replace with your details.
  2. Make sure bin/test is executable
  3. then run and watch for the pings in your slack room
$ bin/test


If there is any thing you'd like to contribute or fix, please:

  • Fork the repo
  • Add tests for any new functionality
  • Make your changes
  • Verify all new & existing tests pass
  • Make a pull request


The slack-notifier gem is distributed under the MIT License.

*Note that all licence references and agreements mentioned in the Slack Notifier README section above are relevant to that project's source code only.