Typosquat

typosquat

A typosquat checker for a dependency list. It reads the package.json of a project, collects every dependency name from dependencies, devDependencies, peerDependencies and optionalDependencies, and compares each name against a bundled list of popular npm package names. A dependency that is not itself a popular package but closely resembles one is flagged as a possible typosquat, with the popular package it resembles named as evidence.

The check is fully offline and deterministic: no network calls, no timestamps, findings sorted by dependency name.

Install

npx @reneturcios/typosquat check .

Or install it globally:

npm install -g @reneturcios/typosquat

typosquat check .

CLI

typosquat check [path] [--json]

typosquat mcp typosquat --version

• check [path]: check the project at path (a directory containing a package.json, or a direct path to a package.json file). Defaults to the current directory. Add --json for the machine readable report.
• mcp: run the MCP server over stdio.
• --version: print the version.

Exit codes: 0 when the verdict is CLEAR, 1 when the verdict is SUSPECT, 2 for usage errors and for a missing or invalid package.json.

Example human output:

typosquat 0.1.0

Target: . Verdict: SUSPECT Dependencies checked: 5 Flagged: 1 Summary: Checked 5 dependencies; 1 flagged as possible typosquats. Findings:

• [HIGH] DISTANCE-1: Dependency "axioss" resembles popular package "axios" (edit distance 1) (evidence: axios)

MCP

The MCP server exposes one tool:

• check_typosquat with a path argument. It returns the same report as the CLI --json output: tool name, version, target, verdict, counts (depsChecked, flagged), findings and a summary.

Matching rules

Names are normalized by lowercasing before comparison. A dependency that is itself in the popular list is never flagged. For every other dependency, the strongest matching rule wins:

• SEPARATOR-SQUAT (high severity): the dependency name equals a popular name once hyphens, underscores and dots are stripped from both names, but the raw names differ. Example: node_fetch vs node-fetch.
• DISTANCE-1 (high severity): Levenshtein edit distance 1 from a popular name. Example: axioss vs axios.
• DISTANCE-2 (medium severity): Levenshtein edit distance 2 from a popular name whose length is 9 or more characters. Short names are excluded at distance 2 because too many unrelated short names sit within two edits of each other. Example: typescrpit vs typescript.

Scope confusion is not checked: an unscoped dependency that equals only the unscoped part of a scoped popular name (for example client vs @prisma/client) is too weak a signal to flag.

Verdict

• CLEAR: no dependency resembled a popular package name.
• SUSPECT: at least one dependency was flagged.

Limits

• The popular package list is a snapshot dated 2026-10-25, written from knowledge of the npm ecosystem. It will drift: new packages become popular and old ones fade, and a snapshot cannot track that.
• Edit distance catches typos, not every squatting style. It does not catch combosquats (a popular name combined with an extra word, such as axios-helper), homoglyph or bit squats, or scope tricks beyond the separator rule above.
• The checker reads names only. It does not inspect package contents, maintainers, download counts or publish history, so it cannot judge malicious intent.
• A flag is a resemblance, not an accusation. Legitimate packages can sit one edit away from a popular name. Treat every finding as a prompt to look, not as proof of wrongdoing.

License

MIT