Lightning YAML

YAML · 1.2 CORE

Parse YAML at JSON speed.
Pass more of the spec than anyone.

Dramatically faster than js-yaml and yaml, and more spec-conformant — 97.6% of the YAML Test Suite — with peak memory close to JSON.parse.

Get started$ pnpm add lightning-yamlSee the benchmarks →

service.yamlYAML

apiVersion: v1
kind: Service
metadata:
  name: billing
spec:
  ports: [{ port: 8080 }]

const svc = parse(src)JS

{
  apiVersion: "v1",
  kind: "Service",
  metadata: { name: "billing" },
  spec: { ports: [{ port: 8080 }] }
}

4.4×

faster than js-yaml

block-YAML parse

39×

faster than yaml

block-YAML parse

97.6%

YAML Test Suite pass

js-yaml 94.9% · yaml 97.1%

≈1.3×

of JSON.parse memory

peak RSS, 10 MB fixture

Anchors, aliases, !!binary & multi-doc streams
parse · parseAll · stringify
js-yaml / yaml drop-in shims
TypeScript-first types
Zero dependencies

Drop-in is API-level today. Imports and call signatures matchjs-yaml and yaml, so existing code runs — but their option arguments (schema, sortKeys, indent, …) are still accepted but ignored. Useful for migrating now; not yet a 1:1 behavioural match.

What we optimise for

Spec-correct

97.6% of the YAML Test Suite — more of the spec than js-yaml(94.9%) or yaml (97.1%).

JSON-class speed

Parses at ~0.5× JSON.parse; 4–39× the JS competition on block YAML.

Lean memory

Peak RSS ≈1.3× JSON.parse — well under js-yaml /yaml.

Small bundle

≈14 kB min+gzip · tree-shakeable · zero deps.

representative target — bundle-size benchmark not wired up yet