How to set up Slack notifications from GitLab CI/CD using the Slack API

#gitlab #cicd #slack #automation

Learn how to integrate Slack with GitLab CI/CD to receive real-time build and deployment notifications directly in your Slack channels. This step-by-step guide walks you through creating a Slack app, configuring the Slack API, and setting up GitLab pipeline jobs to send custom messages for successful builds, failures, and more.

Create a Slack App

1.Go to https://api.slack.com/apps

After signin

2.Click Create New App → From Scratch

3.Give it a name (e.g., GitLab CI Notifier)
4.Choose your workspace

5.Create App

You can add App Icon and App name here

Add Incoming Webhooks

1.In the left sidebar, go to Features → Incoming Webhooks

2.Toggle Activate Incoming Webhooks → ON

3.Click Add New Webhook to Workspace
4.Choose a channel or private group where messages should be sent

5.Copy the Webhook URL:

https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX

Store the Webhook URL in GitLab

1.Go to your GitLab project → Settings → CI/CD → Variables

2.Add a variable:

Edit your .gitlab-ci.yaml

Add a job that sends a message to Slack:

stages:
  - slack_notify

notify_slack:
  stage: slack_notify
  tags:
    - linux-homelab-general-vm
  image:
    name: alpine:latest
  before_script:
    - apk add --no-cache curl
  script:
    - |
      MESSAGE="✅ Pipeline $CI_PIPELINE_STATUS for project $CI_PROJECT_NAME on branch $CI_COMMIT_REF_NAME – $CI_COMMIT_SHORT_SHA"
      echo "Sending Slack notification: $MESSAGE"
      curl -X POST -H 'Content-type: application/json' --data "{\"text\":\"$MESSAGE\"}" "$SLACK_WEBHOOK"
  when: always