Slack node

The Slack node posts a message to a Slack channel through an incoming webhook. It's the quickest way to turn a flow into a team notification — a new signup, a failed payment, a form submission — without wiring up the full HTTP node yourself.

Component id: flowrunner/slack. It makes a network request and can fail for reasons outside your flow, so it carries an error port.

IMPORTANT

This node is an installable component, not part of the engine. Every workspace gets it installed automatically; if it has been removed, the node passes straight through at run time and the editor marks it Not installed in the Add panel. Open Components in the project header to reinstall it.

How it works

The node sends a POST to your Slack webhook URL with a JSON payload:

• Webhook — from webhook, with ${env.X} and ${secrets.X} resolved. A missing webhook fails the node (slack: missing webhook URL). Store the webhook as a secret and reference it with ${secrets.SLACK_WEBHOOK}.
• Message — from text, rendered as a full template: ${secrets.X} / ${env.X} and flow refs like ${start.email} are substituted.
• Username / Icon emoji — optional overrides sent as username and icon_emoji when set.

The request goes through the same hardened, SSRF-guarded fetch as the HTTP node: it re-validates every redirect hop, times out, and caps the response.

WARNING

Changed: the webhook must now point at hooks.slack.com. The component's manifest declares that as the only host it may reach, and the runtime enforces it on every redirect hop. A webhook pointing anywhere else is refused before the request is made (…which its manifest does not allow-list). Previously any URL was accepted, which meant a mistyped or hostile webhook could ship your message data to a third party.

On a 2xx from Slack the node stores an object under resultVar (default slack):

{
  ok: true,
  status: <HTTP status number>
}

A non-2xx response fails the node (slack: webhook returned <status>) and takes the error port.

Config

Field	Required	Description
webhook	Yes	The Slack incoming-webhook URL. Resolves ${env.X} and ${secrets.X}. Missing webhook fails the node.
text	No	The message. Rendered as a template — flow refs (${start.email}), ${env.X}, and ${secrets.X} all resolve.
username	No	Override the display name the message is posted under.
iconEmoji	No	Override the message icon, e.g. :robot_face:. Sent as icon_emoji.
resultVar	No (default slack)	The variable the { ok, status } result is stored under.
retries	No (default 0)	Retry a network error or a retryable status (408/425/429/5xx) up to this many times (max 5). See Retrying transient failures.
retryDelayMs	No	Milliseconds to wait between retries.

Ports

Port	Followed when
next	Slack accepted the message (a 2xx response).
error	The node failed — missing webhook, a non-2xx response, or the request threw (network failure, timeout, blocked address). The message is slack: <reason> and is also written to error.message.

Example

Notify your team channel whenever a contact form is submitted:

Slack  webhook: ${secrets.SLACK_WEBHOOK}
  text: "📥 New enquiry from ${start.name} (${start.email})"
  username: FlowRunner
  iconEmoji: :envelope:
  resultVar: slack
# read later as: slack.ok, slack.status

TIP

Create the webhook in Slack under Apps → Incoming Webhooks, pick the target channel, and paste the generated URL into a workspace secret named SLACK_WEBHOOK. The channel is fixed by the webhook itself — you don't set it in the node.

See also

• HTTP node
• Email node
• Secrets
• Error handling in flows