schemacraft-validator

Schema.org structured data validator — accuracy-matched to validator.schema.org

Installation • Quick Start • CLI • Server • API • Accuracy • Contributing

Why schemacraft-validator?

The Schema Markup Validator (formerly Google's Structured Data Testing Tool) is the industry standard for validating Schema.org markup. SEOs, developers, and tools reference its output as ground truth.

schemacraft-validator brings that same validation to your codebase — as a library, CLI tool, or self-hostable server. No more manual copy-pasting into a web form.

Accuracy-matched — tested against the real validator with real-world schemas; error counts match exactly
All 3 formats — JSON-LD, Microdata, and RDFa extraction from HTML
Raw JSON-LD support — paste the same JSON-LD you'd use on validator.schema.org
Full Schema.org vocabulary — 1003 types, 1676 properties, complete type hierarchy with inheritance
@id cross-references — resolves {"@id": "..."} within @graph structures
SDTT-compatible heuristics — text-for-entity tolerance, URL coercion, string-to-number/boolean
Three interfaces — Library API, CLI, and Express server

Installation

npm install schemacraft-validator

Optional: For JavaScript rendering support (SPAs, dynamically injected JSON-LD):

npm install puppeteer

Quick Start

Library

import { validate, validateMarkup, validateJsonLd } from 'schemacraft-validator';

// Validate a URL
const result = await validate('https://example.com');

// Validate raw HTML
const result = validateMarkup(`
  <html><head>
    <script type="application/ld+json">
    {"@context":"https://schema.org","@type":"Product","name":"Widget"}
    </script>
  </head><body></body></html>
`);

// Validate raw JSON-LD (string or object) — no HTML needed
const result = validateJsonLd({
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Widget Pro",
  "offers": {
    "@type": "Offer",
    "price": "29.99",
    "priceCurrency": "USD"
  }
});

console.log(result.isValid);           // true
console.log(result.summary.types);     // ["Product"]
console.log(result.errors);            // []
console.log(result.warnings);          // []

Batch Validation

import { validateBatch } from 'schemacraft-validator';

const results = await validateBatch([
  'https://example.com/page1',
  'https://example.com/page2',
  'https://example.com/page3',
]);

for (const result of results) {
  console.log(`${result.url}: ${result.isValid ? 'VALID' : 'INVALID'}`);
}

CLI

# Validate a URL
npx schemacraft-validator check https://example.com

# Validate a local HTML file
npx schemacraft-validator check ./page.html

# Validate raw JSON-LD (no HTML wrapper needed)
npx schemacraft-validator check-json ./schema.json

# JSON output (for piping / scripting)
npx schemacraft-validator check https://example.com --format json

# With JavaScript rendering (requires puppeteer)
npx schemacraft-validator check https://spa-example.com --render-js

# Custom timeout
npx schemacraft-validator check https://slow-site.com --timeout 30000

CLI Output Example

Schema Validation Report
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

URL: https://example.com
Status: ✅ Valid (0 errors, 0 warnings)
Entities: 2 found (json-ld)

─── Product ──────────────────────────────────────────
  name                 "Widget Pro"
  description          "The best widget ever made"
  offers               → Offer
    price              "29.99"
    priceCurrency      "USD"

─── Organization ─────────────────────────────────────
  name                 "Example Corp"
  url                  "https://example.com"

Exit Codes

Code	Meaning
`0`	Valid — zero errors
`1`	Invalid — has errors
`2`	Runtime error (fetch failed, file not found, etc.)

Server

Start a self-hostable validation server:

# Start on port 3001
npx schemacraft-validator serve --port 3001

# With secret-based auth (for sidecar deployments)
npx schemacraft-validator serve --port 3001 --secret my-secret-key

Endpoints

`POST /validate`

# Validate a URL
curl -X POST http://localhost:3001/validate \
  -H "Content-Type: application/json" \
  -d '{"url": "https://example.com"}'

# Validate raw HTML
curl -X POST http://localhost:3001/validate \
  -H "Content-Type: application/json" \
  -d '{"markup": "<html>...</html>"}'

# Validate raw JSON-LD
curl -X POST http://localhost:3001/validate \
  -H "Content-Type: application/json" \
  -d '{"jsonld": {"@context":"https://schema.org","@type":"Product","name":"Test"}}'

`POST /validate/batch`

curl -X POST http://localhost:3001/validate/batch \
  -H "Content-Type: application/json" \
  -d '{"urls": ["https://example.com/a", "https://example.com/b"]}'

Max 100 URLs per batch request.

`GET /health`

curl http://localhost:3001/health
# {"status":"ok","version":"1.0.0","uptime":12345}

API Reference

Functions

Function	Input	Returns	Description
`validate(url, options?)`	URL string	`Promise<ValidationResult>`	Fetch URL and validate
`validateMarkup(html, options?)`	HTML string	`ValidationResult`	Validate raw HTML
`validateJsonLd(input, options?)`	JSON string or object	`ValidationResult`	Validate raw JSON-LD
`validateBatch(urls, options?)`	URL array	`Promise<ValidationResult[]>`	Validate multiple URLs

Options

interface ValidateOptions {
  formats?: ('json-ld' | 'microdata' | 'rdfa')[];  // Default: all three
  followRedirects?: boolean;                         // Default: true
  renderJavascript?: boolean;                        // Default: false (needs puppeteer)
  timeout?: number;                                  // Default: 10000ms
  includeRaw?: boolean;                              // Default: false
  headers?: Record<string, string>;                  // Custom HTTP headers
  proxy?: string;                                    // HTTP proxy URL
  userAgent?: string;                                // Default: "SchemaCraftValidator/x.x.x"
}

ValidationResult

interface ValidationResult {
  url?: string;                    // URL validated (undefined for markup/jsonld input)
  timestamp: string;               // ISO 8601 timestamp
  duration: number;                // Processing time in ms
  isValid: boolean;                // true if zero errors (warnings don't count)
  entities: ValidatedEntity[];     // Detected Schema.org entities
  errors: ValidationIssue[];      // All errors
  warnings: ValidationIssue[];    // All warnings
  summary: {
    totalEntities: number;
    totalTriples: number;
    types: string[];               // e.g., ["Product", "Organization"]
    formats: ('json-ld' | 'microdata' | 'rdfa')[];
    errorCount: number;
    warningCount: number;
  };
}

Issue Codes

Code	Severity	Description
`UNKNOWN_TYPE`	error	`@type` is not a recognized Schema.org type
`UNKNOWN_PROPERTY`	error	Property not valid for this type (matches SDTT `INVALID_PREDICATE`)
`INVALID_VALUE_TYPE`	error	Nested entity type doesn't match expected range (matches SDTT `INVALID_OBJECT`)
`MALFORMED_JSONLD`	error	Invalid JSON in script block
`MISSING_TYPE`	error	Missing `@type` on entity
`FETCH_ERROR`	error	HTTP fetch failed
`DEPRECATED_TYPE`	warning	Type is deprecated in Schema.org
`DEPRECATED_PROPERTY`	warning	Property is deprecated
`EMPTY_VALUE`	warning	Property value is empty string

For the full API reference, see docs/API.md.

Accuracy

How We Test

Every release is tested against validator.schema.org to ensure our output matches. We maintain:

22 accuracy fixtures covering JSON-LD, Microdata, RDFa, @graph, @id references, nested entities, mixed formats, edge cases
Real-world validation against production schemas (e.g., ProxyScrape with 19 entities and @id cross-references — matched SDTT's 5 errors / 0 warnings exactly)
Weekly automated accuracy checks via GitHub Actions

Current Accuracy

Metric	Value
Fixture accuracy	100% (22/22)
Test coverage	88.77%
Total tests	203

What We Check (same as validator.schema.org)

Is @type a recognized Schema.org type?
Is each property valid for that type (including inherited from parent types)?
Does each property value match the expected type range?
@id cross-references resolved within @graph
Text-for-entity heuristic (tolerated, per SDTT behavior)
Multiple types, nested entities, deprecated types/properties

Known Divergences

We track every known difference in DIVERGENCES.md. Current divergences:

#	Behavior	Status
1	JS rendering requires `--render-js` flag	By design
2	Entity grouping differs from SDTT display	By design

Supported Formats

Format	Extraction	Validation	Notes
JSON-LD	`<script type="application/ld+json">`	Full	@graph, @id refs, multiple blocks, BOM handling
Microdata	`itemscope`/`itemtype`/`itemprop`	Full	Nested entities, link/img/meta values
RDFa	`typeof`/`property`/`vocab`	Full	Quad grouping, nested entities
Raw JSON-LD	Direct input (no HTML)	Full	Same as pasting into validator.schema.org

Schema.org Vocabulary

The validator ships with a vendored copy of the Schema.org vocabulary containing:

1003 types with full class hierarchy
1676 properties with domain/range definitions
Transitive subtype checking (e.g., LocalBusiness is valid where Organization or Place is expected)
Property inheritance (e.g., Product inherits all Thing properties)

The vocabulary is updated automatically via a weekly GitHub Action that checks for new Schema.org releases.

Use Cases

SEO auditing — validate Schema.org markup before deploying pages
CI/CD pipelines — add schema validation to your build process
Content management — validate markup generated by CMS plugins
API services — self-host a validation endpoint for your platform
Development — catch schema errors during development, not after indexing

Docker

Quick Start

# Build and run
docker compose up -d

# Test it
curl http://localhost:3001/health
curl -X POST http://localhost:3001/validate \
  -H "Content-Type: application/json" \
  -d '{"url": "https://example.com"}'

Configuration

Env Variable	CLI Flag	Default	Description
`BEARER_TOKEN`	`--bearer-token`	(none)	Require `Authorization: Bearer <token>` for API access
—	`--allowed-origins`	`*`	CORS allowed origins (comma-separated)

With Auth

# Via env
BEARER_TOKEN=my-secret-token docker compose up -d

# Call with auth
curl -X POST http://localhost:3001/validate \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer my-secret-token" \
  -d '{"url": "https://nhaphonet.vn"}'

Restrict CORS

# docker-compose.yml
services:
  schema-test:
    # ...
    command: serve --port 3001 --allowed-origins "https://app1.com,https://app2.com"

Verify

# Check the server is running
curl http://localhost:3001/health

# Validate a URL
curl -X POST http://localhost:3001/validate -H "Content-Type: application/json" -d '{"url": "https://example.com"}'

# Validate raw JSON-LD
curl -X POST http://localhost:3001/validate -H "Content-Type: application/json" -d '{"jsonld": {"@context":"https://schema.org","@type":"Product","name":"Test"}}'

# Batch validation
curl -X POST http://localhost:3001/validate/batch -H "Content-Type: application/json" -d '{"urls": ["https://site1.com", "https://site2.com"]}'

Requirements

Node.js >= 18
puppeteer (optional) — only needed for --render-js JavaScript rendering

Attribution

This project is a fork of Google's Schemarama, originally licensed under the Apache License 2.0.

Schema.org vocabulary data is provided by Schema.org under the CC BY-SA 3.0 license.

This project is not affiliated with, endorsed by, or sponsored by Google or Schema.org.

Contributing

We welcome contributions! See CONTRIBUTING.md for guidelines.

git clone https://github.com/Elbradey8/schemacraft-validator.git
cd schemacraft-validator
npm install
npm test          # 203 tests
npm run typecheck # TypeScript strict mode
npm run build     # CJS + ESM + DTS

License

Apache License 2.0 — see NOTICE for attribution details.

Built by Abdullah Elbradey • schemacraft.net

Name		Name	Last commit message	Last commit date
Latest commit History 22 Commits
.github		.github
bin		bin
docs		docs
scripts		scripts
src		src
tests		tests
.dockerignore		.dockerignore
.env.example		.env.example
.gitignore		.gitignore
.npmignore		.npmignore
BRANCHING.md		BRANCHING.md
CHANGELOG.md		CHANGELOG.md
CONTRIBUTING.md		CONTRIBUTING.md
DIVERGENCES.md		DIVERGENCES.md
Dockerfile		Dockerfile
LICENSE		LICENSE
NOTICE		NOTICE
README.md		README.md
docker-compose.yml		docker-compose.yml
eslint.config.js		eslint.config.js
package-lock.json		package-lock.json
package.json		package.json
tsconfig.json		tsconfig.json
tsup.config.ts		tsup.config.ts
vitest.config.ts		vitest.config.ts

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schemacraft-validator

Why schemacraft-validator?

Installation

Quick Start

Library

Batch Validation

CLI

CLI Output Example

Exit Codes

Server

Endpoints

POST /validate

POST /validate/batch

GET /health

API Reference

Functions

Options

ValidationResult

Issue Codes

Accuracy

How We Test

Current Accuracy

What We Check (same as validator.schema.org)

Known Divergences

Supported Formats

Schema.org Vocabulary

Use Cases

Docker

Quick Start

Configuration

With Auth

Restrict CORS

Verify

Requirements

Attribution

Contributing

License

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