Every option, and what it can and cannot change
Indent sets spaces per level; “Indent sequences” chooses between the indented list style and the flush “kubectl” style. Line width folds long plain and quoted strings — block scalars (| and >) keep their lines exactly. Quote style can switch string values to double, single or plain quotes; a plain form that would read as another type is kept quoted, and with “Quote YAML 1.1 hazards” words like no, on, y and dates stay quoted too.
Collections can stay as written, become block (indented) or flow ({ } and [ ]). Converting to flow is blocked when comments inside the collection would be lost. Line endings and the UTF-8 byte-order mark are preserved by default and changed only when you choose.
How the result is checked
The formatted text is parsed independently under the same profile and compared node by node with the source: scalar type and exact value, collection kind, explicit tags, mapping keys, and which nodes are shared through anchors. Key order changes are refused here — sorting is a separate, explicit operation.
Comments are inventoried with the YAML lexer, so a # inside a string is never mistaken for one. Lost comments block the result; moved comments are listed with their old and new attachment.
Questions
- Which YAML version is used?
- YAML 1.2.2 with the core schema by default. You can switch to the JSON or failsafe schema, or to YAML 1.1 for legacy tools. A %YAML directive inside a document overrides the choice for that document, and the Checks tab says so.
- Can I save my own preset?
- Yes. On the Presets page you can save options under a name, export them as a small JSON file and import a teammate’s file. Preset files are validated and never executed.
- Why are merge keys (<<) off by default?
- Merge keys were a YAML 1.1 extension and are not part of YAML 1.2. FormatYAML keeps << as written either way; the profile switch only affects how JSON conversion interprets it.