package.json validator

Client

Quick package.json lint.

Learn more: package.json validator

Run a quick browser-based preflight on package.json syntax and common fields such as name and version before publishing, installing, or sharing a minimal reproduction.

Required input

Paste the complete package.json object. The checker parses JSON first, then reports common manifest-shape warnings that are easy to miss in hand-edited files.

What the result means

This is not the package registry and does not resolve dependencies, execute lifecycle scripts, or guarantee that a package can be published. Run your package manager checks before release.

Local processing

The page parses and transforms the pasted document in your browser. Use a smaller representative sample first when the source is large.

What this page does

Run a quick browser-based preflight on package.json syntax and common fields such as name and version before publishing, installing, or sharing a minimal reproduction.

Input and workflow

Paste the complete package.json object. The checker parses JSON first, then reports common manifest-shape warnings that are easy to miss in hand-edited files. Start with Load example or prefill the primary input with ?q= / ?qb=.

Scope and limits

This is not the package registry and does not resolve dependencies, execute lifecycle scripts, or guarantee that a package can be published. Run your package manager checks before release.

The operation runs in your browser. Large documents may slow the tab, so test a representative sample before processing more data.

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Nearby workflows on Toolcore

Common use cases

  • Catch malformed JSON or an invalid name/version field before a package publish attempt.
  • Review a reduced package.json while preparing a reproducible issue.
  • Check a generated manifest before saving it into a project.

Common mistakes to avoid

  • Assuming dependency versions are resolved

    The page checks manifest shape only; it does not contact a registry or verify that dependency ranges exist.

  • Including comments or trailing commas

    package.json is strict JSON. Remove comments and trailing commas before validation.

  • Treating a clean result as publish approval

    Registry policy, files included in the package, scripts, and authentication still need separate checks.

FAQ

Does this install package dependencies?

No. It only inspects the pasted manifest.

Is package.json sent to a server?

No. Parsing and checks run in your browser.

Does it support JSON comments?

No. package.json requires strict JSON, so comments are reported as syntax errors.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • package json validator online
  • validate npm package json
  • package json syntax checker
  • package json name version check

More tools

Related utilities you can open in another tab—mostly client-side.