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js-yaml 5.0.0

npm / js-yaml / 5.0.0 source ↗

[5.0.0] - 2026-06-20

Added

  • Added named exports for schemas, tags, parser events and AST utilities.
  • Reworked JSON_SCHEMA and CORE_SCHEMA with spec-compliant scalar resolution rules, and added YAML11_SCHEMA.
  • Added realMapTag for lossless mappings with non-string and complex keys. Object-based mappings now reject complex keys instead of stringifying them.
  • Added dump() transform option for changing the generated AST before rendering.
  • Added dump() options seqInlineFirst, flowBracketPadding, flowSkipCommaSpace, flowSkipColonSpace, quoteFlowKeys, quoteStyle and tagBeforeAnchor.
  • Added formal data layers (events and AST) for modular data pipelines.
    • Added low-level parser (to events), presenter and visitor APIs.
  • Added the YAML Test Suite to the test set.

Changed

  • See the migration guide for upgrade notes.
  • Rewritten in TypeScript and reorganized the public API around flat named exports.
  • Reduced the set of exported schemas:
    • YAML 1.2 schemas: CORE_SCHEMA (loader default), JSON_SCHEMA, FAILSAFE_SCHEMA.
    • YAML11_SCHEMA, a combination of all YAML 1.1 tags (YAML 1.1 does not specify a schema, only "types").
  • load/dump default behaviour is now specified exactly via schemas:
    • load uses CORE_SCHEMA, without !!merge by default.
    • dump uses YAML11_SCHEMA + CORE_SCHEMA for the quoting check, to guarantee backward compatibility by default.
  • !!set is now loaded as a JavaScript Set.
  • Replaced the Type API with a tags API. Similar, but more precise and simpler. See examples for details. Tags can be defined via defineScalarTag(), defineSequenceTag() and defineMappingTag(), or as a spread + override of an existing tag.
  • Renamed Schema.extend() to Schema.withTags().
  • Expanded YAML 1.2 conformance and improved handling of directives, document markers, block keys, multiline scalars, tag syntax and other things.
  • load() now throws on empty input instead of returning undefined.
  • Moved browser builds to the js-yaml/browser export.
  • Deprecated the loadAll signature with an iterator (still works, but is a candidate for removal).

Removed

  • Removed deprecated safeLoad(), safeLoadAll() and safeDump() exports.
  • Removed DEFAULT_SCHEMA and the nested types export.
  • Removed loader options onWarning, legacy and listener.
  • Removed dumper options styles, replacer, noCompatMode, condenseFlow, quotingType and forceQuotes. Renamed noArrayIndent to seqNoIndent. Formatting and representation are now configured through presenter options, schemas and tag definitions. See migration guide on how to replace.
  • Removed support for importing internal files from lib/.