Internal Developer Portals (IDPs) provide a unified self-service interface over the tools, services, and infrastructure that developers use day-to-day — exposing a service catalog, scorecards, golden-path templates, and one-click actions for provisioning, deployments, and access. Core capabilities include a software catalog with ownership metadata and dependency mapping; scorecards that measure service maturity against platform standards (has runbook, has SLO, patched dependencies); golden-path templates that scaffold new services with production-ready defaults; and self-service workflows that abstract underlying tools (Kubernetes, Terraform, cloud consoles) behind developer-friendly forms. Leading options include Spotify Backstage (OSS-led), Port, Cortex, OpsLevel, Roadie, Humanitec, and Atlassian Compass.