Sidecar files let you define metadata in a separate file.

They are similar to front matter in that the metadata in a sidecar file is applied to a document, but instead of the metadata being defined at the top of a file, it's defined alongside the file. Sidecar files can be JSON or YAML and are typically named _[filename].json or _[filename].yaml.

Sidecar file support can be globally turned off by setting ProcessSidecarFiles to false.