Post alerts with a Slack webhook

Post ilert alerts to a Slack channel through a Slack incoming webhook, where the ilert app cannot be installed.

Prefer the ilert app for Slack. A webhook only posts messages: nobody can accept, reroute, or resolve from the channel, the message is never updated as the alert changes, and the slash commands do not exist. Use this route only where your workspace will not grant the ilert app its permissions.

In Slack: create an incoming webhook

Create a Slack app for your workspace, enable Incoming Webhooks, and add a webhook for the channel you want alerts in. Slack's own guide, Sending messages using incoming webhooks, walks through it.

Copy the webhook URL Slack gives you. It starts with https://hooks.slack.com/services/ and ends in three path segments that identify the workspace, the channel, and the webhook's own secret.

Treat that URL as a secret. Anyone who has it can post to your channel.

In ilert: create the alert action

1

Start a new alert action

In the sidebar, go to Alerting → Alert actions and click Create new alert action.

2

Choose Slack, with the webhook option

Select the Slack tile and tick Use webhook. Click Next.

3

Choose the alert sources and the events to publish

Pick the alert sources whose alerts should reach the channel, and tick the events to publish. Only Alert created is ticked to begin with, and every event you add becomes its own message in the channel. Click Next.

4

Skip the conditions

Set conditions under Conditional execution, or click Next to publish every alert of those sources.

5

Paste the webhook URL

Name the alert action, paste the URL into URL, and click Save. Click Save again on the edit page to reach the detail page.

6

Test it

Click Test in the top right. A test message appears in the channel.

What arrives in the channel

Each message carries the alert's status and summary as a link into ilert, the alert details, and the first image attached to the alert. A comment event carries the comment and its author. The color follows the status: red while pending, yellow once accepted, green when resolved.

Messages are always in English, and there are no buttons. Every event you tick posts a new message, so a busy alert produces a series of messages rather than one that keeps up to date.

FAQ

Can I use several webhooks?

Yes. Create one alert action per webhook URL, each with its own channel and its own trigger events.

The messages stopped arriving

Open the alert action and read Alert action logs on its detail page. Slack rejects a webhook whose app was removed from the workspace, or whose channel was deleted; create a new webhook in Slack and paste the new URL into the alert action.

Can I change how the message looks?

No. The Slack webhook alert action has no message template. The ilert app gives the richer card, and the generic webhook integration gives full control over the payload.