YAML Formatter & Validator

YAML 1.2 via js-yaml — the same parser used in many CI tools. Anchors (&) and references (*) are accepted; merge keys (<<: *anchor) are always merged into the mapping that uses them.

No. js-yaml drops comments because the YAML spec doesn't attach them to nodes. If your YAML has critical comments, format a section at a time and paste comments back manually.

When on, the formatter inlines anchored values everywhere they're referenced, so the output has no & / * markers. Off writes a shared object as an anchor and reference again, but under a generated name such as ref_0, and an aliased scalar still comes out in full.

100 columns is a common compromise for reviewing code and config — wide enough for most inline scalars without word-wrapping in diffs.

No, and this is worth knowing: that behaviour belongs to YAML 1.1. Under the YAML 1.2 core schema this parser uses, only true and false are booleans, so no, yes, on and off all stay strings and a country column of NO survives intact. The caveat is that not every tool has moved: PyYAML's default loader is still 1.1, so a file that round-trips correctly here can still flip on the other side. That is why the formatter emits 'yes' in quotes — the quoting protects the value from readers that are stricter about it than this one.

Because unquoted 1.10 is a float, and 1.10 and 1.1 are the same float. Version strings, phone numbers with leading zeros, and part codes all need quotes to survive: write "1.10". The related trap is octal — YAML 1.2 dropped the bare leading-zero form, so a file mode written as 0755 parses as the decimal number 755, not 493. Write 0o755 if you mean octal, or quote it if you mean the literal text.