HCL overview

HCL (HashiCorp Configuration Language) is a structured configuration language designed to be both human-readable and machine-parseable. It is the primary language for Terraform infrastructure definitions, Packer build templates, Vault policies, and Nomad job specs. HCL supports expressions, loops (for_each, count, dynamic blocks), functions, locals, and module composition. Its type system supports strings, numbers, booleans, lists, maps, and objects. The HCL2 version introduced more powerful expression semantics. Terraform-specific HCL adds provider, resource, data, and output blocks that drive infrastructure-as-code workflows across AWS, GCP, Azure, and hundreds of other providers via the Terraform Registry.