json-validate

Validate JSON data against a JSON Schema (draft-07 core) with readable error messages. Zero dependencies.

The natural companion to json-schema-gen: generate a schema from a sample, then enforce it in CI. Unlike ajv-cli, this pulls in no dependencies.

---

Install

npm install -g json-validate

Or without installing:

npx json-validate schema.json data.json

---

Usage

json-validate schema.json data.json                    # Validate one file
json-validate schema.json user1.json user2.json        # Validate several
json-validate -s schema.json data.json --quiet         # Exit code only
json-validate schema.json data.json --json             # Machine-readable

---

Example

schema.json:

{
  "type": "object",
  "required": ["id", "email", "age"],
  "properties": {
    "id":    { "type": "string", "format": "uuid" },
    "email": { "type": "string", "format": "email" },
    "age":   { "type": "integer", "minimum": 0, "maximum": 120 },
    "role":  { "enum": ["admin", "user", "guest"] }
  },
  "additionalProperties": false
}

data.json:

{ "id": "not-a-uuid", "email": "bad", "age": 200, "role": "wizard", "extra": true }

Running json-validate schema.json data.json:

json-validate  schema: schema.json

  ✗ data.json  5 errors
      .id     is not a valid uuid
      .email  is not a valid email
      .age    must be <= 120 (is 200)
      .role   must be one of ["admin","user","guest"]
      (root)  additional property 'extra' is not allowed

  0 valid  1 invalid

---

Supported Keywords

Category	Keywords
Core	type, enum, const
Object	required, properties, patternProperties, additionalProperties, minProperties, maxProperties
Array	items (incl. tuples), minItems, maxItems, uniqueItems
Number	minimum, maximum, exclusiveMinimum, exclusiveMaximum, multipleOf
String	minLength, maxLength, pattern, format
Combinators	allOf, anyOf, oneOf, not

Formats: date-time, date, time, email, uri, uuid, ipv4, ipv6, hostname

---

CI Integration

- name: Validate config against schema
  run: npx json-validate config.schema.json config.json --quiet

Exit codes:

• 0 — all data files valid
• 1 — at least one invalid
• 2 — file missing or malformed JSON

---

Scope

This validates the draft-07 core keywords listed above — covering the vast majority of real-world schemas. It does not resolve $ref/$defs or remote references; keep schemas self-contained. For full draft-2020-12 + $ref resolution, use ajv.

---

License

MIT

---

Keywords

json schema validator · validate json · ajv alternative · ajv-cli alternative · json validation · draft-07 · schema check · validate against schema · zero dependencies · ci

---

Built to solve, shared to help — Rushabh Shah 🛠️✨

_{One of 40+ zero-dependency developer CLI tools — no node_modules, ever.}