--- title: "js-yaml Breaking Changes on npm | Since.dev" description: "What each js-yaml release removed, renamed or changed: 67 breaking changes in 4 versions on npm, each with its source." canonical_url: https://since.dev/packages/npm/js-yaml last_updated: 2026-08-26 --- # js-yaml breaking changes Every breaking API change we have recorded in js-yaml on npm: 67 breaking changes in 4 versions. Below are its newest 4 versions, removals and renames first, each with its source. Newest change August 26, 2026 ## 5.0.0 60 breaking changes, first published June 20, 2026. - **Removed** Deep imports of internal files under lib/ no longer work; use the public exports instead. [github.com](https://github.com/nodeca/js-yaml/blob/5.0.0/CHANGELOG.md) - **Removed** `DEFAULT_SCHEMA` DEFAULT_SCHEMA is no longer exported; use one of the remaining schemas such as CORE_SCHEMA. [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.CORE_SCHEMA` CORE_SCHEMA was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.dump` dump was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.DumpOptions` DumpOptions was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.FAILSAFE_SCHEMA` FAILSAFE_SCHEMA was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.JSON_SCHEMA` JSON_SCHEMA was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.load` load was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.loadAll` loadAll was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) - **Removed** `default.LoadOptions` LoadOptions was removed in js-yaml 5.0.0 [npmjs.com](https://www.npmjs.com/package/js-yaml/v/5.0.0) And 50 more in this version. ## 4.3.2 2 breaking changes, first published August 26, 2026. - **Behavior changed** Merge sequences larger than 100 entries are now rejected. Documents that relied on bigger merge sequences must be split or reduced. [github.com](https://github.com/nodeca/js-yaml/blob/4.3.2/CHANGELOG.md) - **Behavior changed** `maxTotalMergeKeys` Empty mappings inside merge sequences now count toward the maxTotalMergeKeys limit, so some documents that previously loaded may now be rejected. [github.com](https://github.com/nodeca/js-yaml/blob/4.3.2/CHANGELOG.md) ## 4.3.0 1 breaking change, first published June 26, 2026. - **Removed** `maxMergeSeqLength` The maxMergeSeqLength loader option was removed and replaced by maxTotalMergeKeys, which limits the total number of keys processed by YAML merge per load call. Switch uses of maxMergeSeqLength to maxTotalMergeKeys. [github.com](https://github.com/nodeca/js-yaml/blob/4.3.0/CHANGELOG.md) ## 4.2.0 4 breaking changes, first published May 31, 2026. - **Behavior changed** Documents with top-level block scalars lacking content indentation now fail to parse. Fix the input YAML to add the indentation. [github.com](https://github.com/nodeca/js-yaml/blob/4.2.0/CHANGELOG.md) - **Behavior changed** YAML values containing underscores, such as 1_000, are no longer resolved as numbers. Code that relied on them being numeric must convert them explicitly. [github.com](https://github.com/nodeca/js-yaml/blob/4.2.0/CHANGELOG.md) - **Behavior changed** `maxDepth` Loading YAML nested deeper than the default limit of 100 now throws a dedicated error. Raise maxDepth if deeper documents must load. [github.com](https://github.com/nodeca/js-yaml/blob/4.2.0/CHANGELOG.md) - **Behavior changed** `maxMergeSeqLength` Merge sequences longer than the default limit of 20 are now rejected. Raise maxMergeSeqLength if longer merges must load. [github.com](https://github.com/nodeca/js-yaml/blob/4.2.0/CHANGELOG.md) ## Check your code These are the changes. To see which of them reach your code, [scan a public repository](https://since.dev/scan.md), or have your coding agent call `check_code` with your manifest or lockfile over [MCP](https://since.dev/docs.md#mcp). [The API](https://since.dev/docs.md#api) reads every change in every version, not only the newest. On Team and up, a fix pull request opens for the changes that reach a connected repository. Nothing merges or deploys. ## Put your code on continuous management. Scan a public repository now, or give your agent one line. ### See how out of date your code is. [Scan a repository](https://since.dev/scan.md). Any public GitHub repository. No sign-in. ### Tell your agent what changed since it was trained. `claude mcp add --transport http since https://api.since.dev/mcp` --- Every page on this site as Markdown: https://since.dev/sitemap.md. For agents: https://since.dev/llms.txt.