This error occurs when npm can't flatten the dependency tree to remove duplicates. Usually caused by version conflicts or peer dependency issues that prevent deduplication.
The EDEDUPE error means npm's deduplication algorithm failed. `npm dedupe` tries to flatten the dependency tree by moving duplicate packages to higher levels, reducing overall node_modules size. Deduplication fails when: - Multiple packages require incompatible versions of the same dependency - Peer dependency requirements conflict - The dependency tree structure makes deduplication impossible - Package-lock.json has conflicts that can't be resolved
Start fresh with a new dependency tree:
rm -rf node_modules package-lock.json
npm installThis often resolves conflicts that built up over time.
Prevent duplicates from occurring:
npm install --prefer-dedupeThis tells npm to prefer deduplication during installation.
See what would be deduplicated:
npm find-dupesThis shows duplicate packages without making changes.
Relax peer dependency checking:
npm dedupe --legacy-peer-depsOr during install:
npm install --legacy-peer-depsForce a specific version of a problematic package (npm 8.3+):
{
"overrides": {
"problematic-package": "1.2.3"
}
}Then reinstall:
rm -rf node_modules package-lock.json
npm installCheck which packages have conflicts:
npm ls duplicate-package-nameUpdate packages that depend on outdated versions:
npm update parent-packageWhat dedupe does: npm dedupe reorganizes node_modules to reduce duplicates. It moves dependencies as high in the tree as possible while maintaining compatibility.
Why duplicates happen: When package A needs [email protected] and package B needs [email protected], npm might install both if they can't be merged. Dedupe tries to find a version that satisfies both.
Dedupe vs install:
- npm install creates the initial tree
- npm dedupe optimizes an existing tree
- npm install --prefer-dedupe combines both
Workspace limitations: npm dedupe has known issues with workspaces in some npm versions. Update to the latest npm or use clean reinstall instead.
When dedupe isn't possible: Some version conflicts can't be resolved. If two packages genuinely need different major versions of a dependency, you'll have to accept duplicates.
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