Convert YAML to CSV Online

YAML to CSV makes sense when a YAML file is really a table: a list of records that all share roughly the same keys. Test fixtures, seed data, inventory lists, Jekyll and Hugo data files and exported config catalogues often look like this. Turning them into CSV lets you sort and filter in a spreadsheet, or load them into a database with COPY.

The file must be a list at the top level, with one mapping per record, each starting with a dash. If the list sits under a key, such as items: at the top of the file, the whole file becomes a single row. Remove the wrapper key and outdent the list first. Records do not need identical keys. Every key seen becomes a column, and records without it get an empty field.

CSV is flat, so nested data is the main problem. A list value such as tags: [red, blue] is written as JSON text, ["red","blue"], inside one quoted field. A nested mapping is not split into columns either; it is kept as JSON text too. Run the Flatten YAML tool first so a city key under address becomes its own address_city column. Unquoted dates such as 2026-03-02 are read as timestamps by the YAML parser and written as 2026-03-02T00:00:00.000Z. Quote them in the YAML to keep plain dates.