Incoming Webhooks are a simple way to post messages from external sources into Slack. They make use of normal HTTP requests with a JSON payload that includes the message text and some options. Message Attachments can also be used in Incoming Webhooks to display richly-formatted messages that stand out from regular chat messages.
Start by setting up an incoming webhook integration in your Slack team to try these features out:
Use curl, a simple, ubiquitous tool for sending HTTP requests on the command line, for the curl examples that follow.
Let's learn how to send this in-channel message as an incoming webhook:
It's a simple, multi-line message without special formatting:
This is a line of text.
And this is another one.
The first step is to prepare this message as a key/value pair in JSON. For a simple message, your JSON payload only needs to define a text property, containing the text that will be posted to the channel.
In JSON, our message is defined as:
{
"text": "This is a line of text.\nAnd this is another one."
}
Please note that we indicated the line break as the control character \n. We also added additional whitespace for readability, which we could have more tidily presented to you as:
{"text":"This is a line of text.\nAnd this is another one."}
Once you've put together the JSON for your message, you can choose to send it to your Incoming Webhook URL one of two ways:
The preferred way to send Slack your JSON body is by sending a HTTP POST to your webhook URL, containing a request body with an explicit Content-type HTTP header set to application/json. This tells Slack how to interpret the data you're sending us.
POST https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
Content-type: application/json
{
"text": "This is a line of text.\nAnd this is another one."
}
By declaring the content type, no further encoding of the POST body is needed — just provide valid JSON in UTF-8.
curl -X POST -H 'Content-type: application/json' --data '{"text":"This is a line of text.\nAnd this is another one."}' https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
If you want to stick with the more traditional Content-type of application/x-www-form-urlencoded, you can sneakily send URL-escaped JSON within the payload parameter instead.
Send the payload parameter as part of your POST body and explicitly state the Content-type. Payloads should not be included as query parameters on the webhook URL.
The trickiest part of this approach is that you must properly URL encode your payload. Your elegant JSON message becomes seeming nonsense, filled with percent-encoded characters.
POST https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
Content-type: application/x-www-form-urlencoded
payload=%7B%22text%22%3A%22This%20is%20a%20line%20of%20text.%5CnAnd%20this%20is%20another%20one.%22%7D
Many HTTP clients provide convenient functions for URL encoding and setting the Content-type.
curl -X POST --data-urlencode 'payload={"text":"This is a line of text.\nAnd this is another one."}' https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
Using the --data-urlencode curl parameter automatically URL encodes the provided string.
To create a link in your text, enclose the URL in <> angle brackets. For example: payload={"text": "<https://slack.com>"} will post a clickable link to https://slack.com.
To display hyperlinked text instead of the actual URL, use the pipe character, as shown in this example:
{
"text": "<https://alert-system.com/alerts/1234|Click here> for details!"
}
This will be displayed in the channel as:
Though it is best to use a single incoming webhook for a specific purpose, in some cases you may want to override the default channel and authoring identity of an incoming webhook.
You cannot override the default username, icon, or channel for incoming webhooks attached to Slack apps. Instead, these values will stubbornly inherit from the associated Slack app configuration.
Incoming webhooks originate from a default identity you configured when originally creating your webhook. You can override a custom integration's configured name with the username field in your JSON payload.
You can also override the bot icon either with icon_url or icon_emoji.
{
"username": "ghost-bot",
"icon_emoji": ":ghost:",
"text": "BOO!"
}
An overridden username and icon could look like this:
Incoming webhooks output to a default channel and can only send messages to a single channel at a time. You can override a custom integration's configured channel by specifying the channel field in your JSON payload.
Specify a Slack channel by name with "channel": "#other-channel", or send a Slackbot message to a specific user with "channel": "@username".
{
"channel": "#other-channel",
"text": "This message will appear in #other-channel"
}
If you prefer, you can also specify a channel ID or user ID like so: "channel": "U024BE7LH".
You can use Slack's standard message markup to add simple formatting to your messages. You can also use message attachments to display richly-formatted message blocks.
Use the Message Builder to preview your message formatting and attachments in real time!
Here is a sample curl command for posting to a channel using the payload parameter:
curl -X POST --data-urlencode 'payload={"text": "This is posted to <#general> and comes from *monkey-bot*.", "channel": "#general", "username": "monkey-bot", "icon_emoji": ":monkey_face:"}' https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
And here is a version using a Content-type of application/json:
curl -X POST -H 'Content-type: application/json' --data '{"text": "This is posted to <#general> and comes from *monkey-bot*.", "channel": "#general", "username": "monkey-bot", "icon_emoji": ":monkey_face:"}' https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
With either approach, this will be displayed in the #general channel as:
You will be able to set up an incoming webhook when you create a Slack app and configure a Slack button.
Once a user installs your app, you will exchange the code for an access token using the oauth.access method. The JSON response from this API call will contain the access token and incoming webhook URL:
{
"access_token": "xoxp-XXXXXXXX-XXXXXXXX-XXXXX",
"scope": "incoming-webhook",
"team_name": "Team Installing Your Hook",
"incoming_webhook": {
"url": "https://hooks.slack.com/TXXXXX/BXXXXX/XXXXXXXXXX",
"channel": "#channel-it-will-post-to",
"channel_id": "C05002EAE",
"configuration_url": "https://teamname.slack.com/services/BXXXXX"
}
}
Keep in mind that incoming webhooks packaged as Slack apps cannot override the default channel, username, or icon associated with the webhook.
Create a Slack app to package and distribute your incoming webhook and share it in our application directory.