What is Atlantis and how does it automate Terraform?

Answer

Atlantis is an open-source tool that automates Terraform pull request workflows. When a developer opens a PR with Terraform changes, Atlantis automatically runs terraform plan and posts the output as a PR comment. Team members review the plan and approve. After approval, a atlantis apply comment triggers the apply. Benefits: Plan visibility: everyone sees exactly what will change before merging. Apply gating: requires human approval (and optionally successful CI) before applying. No local apply: developers never run apply locally — all applies go through the PR workflow with a full audit trail. Webhook-driven: Atlantis runs on a server (or as a Kubernetes pod) and listens to GitHub/GitLab webhooks. Configuration: atlantis.yaml defines which Terraform paths to watch and workspace configurations. Atlantis is the most popular open-source alternative to Terraform Cloud for teams wanting GitOps-based Terraform automation on their own infrastructure.