Web Server

The Web Server is the Flask-based process that serves the Airflow UI — it reads DAG and task state from the metadata database and renders it as web pages, and handles manual actions triggered from the UI (like triggering a run or marking a task as failed).

Key points:

• Read-mostly — it displays state written by the Scheduler; it doesn’t schedule anything itself
• Separate process — runs independently of the Scheduler, so the UI can stay up even if scheduling is paused
• Auth & RBAC — handles login and role-based access to DAGs and views

See also: Scheduler, UI