.yaml File — YAML Ain't Markup Language

YAML (YAML Ain't Markup Language, originally Yet Another Markup Language) is a human-friendly data serialization format widely used for configuration files, data exchange, and infrastructure-as-code definitions. Created by Clark Evans in 2001, YAML uses indentation-based structure with minimal syntax — no brackets, braces, or quotes required for most values — making it exceptionally readable for configuration purposes. YAML supports scalars (strings, numbers, booleans, null, dates), sequences (lists), mappings (dictionaries), multi-line strings (literal and folded blocks), anchors and aliases for data reuse, custom tags, and multiple documents in a single file. YAML is the standard configuration format for Docker Compose, Kubernetes, GitHub Actions, GitLab CI, Ansible, Helm charts, Spring Boot, and countless DevOps tools. The format is a superset of JSON — all valid JSON is also valid YAML. YAML's readability advantages come with pitfalls: the "Norway problem" (no being interpreted as false), implicit type conversion, and indentation sensitivity can cause subtle bugs. YAML 1.2 (the current version) addressed some of these issues.