Why This Conversion Isn't Always Lossless
Converting JSON to YAML is straightforward — YAML is a strict superset of JSON's data model, so every JSON value has a direct YAML equivalent. Converting YAML to JSON is where real information can be lost: YAML comments have no JSON equivalent and are simply dropped, YAML's multi-document files (multiple ----separated documents in one file) don't map to single JSON documents, and YAML's more flexible scalar syntax (multiple ways to write the same value) collapses down to JSON's stricter, single-representation types.
This asymmetry is worth understanding before relying on a round-trip conversion for anything beyond a quick format change — converting YAML to JSON and back to YAML won't necessarily reproduce the original file exactly, since comments and formatting choices don't survive the JSON intermediate step (see Complete Guide to Data Conversion for the deeper explanation of why this specific direction loses information).
For straightforward data (no comments, single document, unambiguous scalars) the conversion is fully reversible — the loss only becomes relevant once a YAML file uses features that exist specifically because YAML is a superset, not just an equivalent notation.