text/yaml

The label two decades of tooling invented while waiting for a real one: text/yaml, text/x-yaml, and application/x-yaml all circulated for YAML documents because the format went from 2001 until 2024 with no registered type at all. RFC 9512 finally settled the question — the canonical type is application/yaml, together with a +yaml suffix for derived formats — so this text/ variant is now officially the wrong answer that everything still sends. Configs, CI pipelines, and Kubernetes manifests will keep it alive in mime tables regardless; if you control the server, send application/yaml and be one of the few who does.

.yaml is the project-preferred spelling; .yml persists from DOS-length habit.

Defined by RFC 9512. Registry facts from the IANA media-types registry via mime-db.