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.