epubcheck-ts

Validate EPUB files in Node.js and the browser. A TypeScript implementation of EPUBCheck.

Status: Measured against EPUBCheck 5.4.0 across 763 spec fixtures — 95.9% agreement on whether a publication is valid, 87.5% agreement on which errors and warnings are reported. See PROJECT_STATUS.md for the full breakdown and methodology. For formal EPUB 3 conformance certification, use the official Java EPUBCheck.

Features

• CLI and API — Use as a CLI tool (npx @likecoin/epubcheck-ts book.epub) or import as a library
• Browser support — Works in Node.js 18+ and modern browsers via pure JS + WASM
• No native dependencies — No Java, no compilation — npm install and go
• TypeScript — Full type definitions included
• Tree-shakable — ESM with proper exports for minimal bundle impact

Try it Online

Live demo at likecoin.github.io/epubcheck-ts — validate EPUB files in the browser without uploading to any server.

Installation

npm install @likecoin/epubcheck-ts

Quick Start

Command Line Interface (CLI)

Quick validation:

npx @likecoin/epubcheck-ts book.epub

Or install globally:

npm install -g @likecoin/epubcheck-ts
epubcheck-ts book.epub

CLI Options:

epubcheck-ts <file.epub> [options]

Options:
  -j, --json <file>        Output JSON report to file (use '-' for stdout)
  -q, --quiet              Suppress console output (errors only)
  -p, --profile <name>     Validation profile (default|dict|edupub|idx|preview)
  -m, --mode <type>        Validation mode: exp (expanded directory), opf, xhtml, svg, nav, mo
  -v, --epub-version <ver> EPUB version for single-file mode (2|2.0|3|3.0|3.1|3.2|3.3)
  -u, --usage              Include usage messages (best practices)
  -f, --fatal              Show only fatal errors
  -e, --error              Show fatal errors and errors
  -w, --warn               Show fatal errors, errors, and warnings
  -i, --info               Show fatal, error, warning, and info messages
  -c, --customMessages <file>  Override message severities (TSV: ID<tab>SEVERITY)
      --fail-on-warnings   Exit with code 1 if warnings are found
                           (also accepts --failonwarnings for Java compatibility)
  -l, --listChecks         List all message IDs and severities
  -V, --version            Show version information
  -h, --help               Show this help message

-w and --fail-on-warnings are different options: -w only widens which messages are displayed, while --fail-on-warnings changes the exit code. Use the latter in CI. Note also that -V shows the version — -v takes an EPUB version for single-file mode.

Examples:

# Basic validation
epubcheck-ts book.epub

# Generate JSON report
epubcheck-ts book.epub --json report.json

# Quiet mode for CI/CD
epubcheck-ts book.epub --quiet --fail-on-warnings

# Validate with specific profile
epubcheck-ts dictionary.epub --profile dict

# Show only errors (hide warnings/info)
epubcheck-ts book.epub --error

# Enable suppressed accessibility checks
printf "ACC-004\tWARNING\nACC-005\tWARNING\n" > overrides.txt
epubcheck-ts book.epub -c overrides.txt

ES Modules (recommended)

import { EpubCheck } from '@likecoin/epubcheck-ts';
import { readFile } from 'node:fs/promises';

// Load EPUB file
const epubData = await readFile('book.epub');

// Validate
const result = await EpubCheck.validate(epubData);

if (result.valid) {
  console.log('EPUB is valid!');
} else {
  console.log(`Found ${result.errorCount} errors and ${result.warningCount} warnings`);
  
  for (const message of result.messages) {
    console.log(`${message.severity}: ${message.message}`);
    if (message.location) {
      console.log(`  at ${message.location.path}:${message.location.line}`);
    }
  }
}

CommonJS

const fs = require('node:fs');

async function validate() {
  const { EpubCheck } = require('@likecoin/epubcheck-ts');

  const epubData = fs.readFileSync('book.epub');
  const result = await EpubCheck.validate(epubData);

  console.log(result.valid ? 'Valid!' : 'Invalid');
}

validate();

The XML engine (libxml2-wasm, ESM-only with top-level await) is lazy-loaded inside EpubCheck.validate(), so the package stays require()-able from CommonJS and importable without forcing top-level-await support on your bundler.

Browser

import { EpubCheck } from '@likecoin/epubcheck-ts';

// From file input
const fileInput = document.querySelector('input[type="file"]');
fileInput.addEventListener('change', async (event) => {
  const file = event.target.files[0];
  const data = new Uint8Array(await file.arrayBuffer());
  
  const result = await EpubCheck.validate(data);
  console.log(result);
});

API

Full API reference: online | markdown

EpubCheck.validate(data, options?)

Static method to validate an EPUB file.

Parameters:

• data: Uint8Array - The EPUB file contents
• options?: EpubCheckOptions - Optional validation options

Returns: Promise<EpubCheckResult>

new EpubCheck(options?)

Create a reusable validator instance.

const checker = new EpubCheck({
  version: '3.3',
  profile: 'default',
  locale: 'en',
});

const result1 = await checker.check(epub1Data);
const result2 = await checker.check(epub2Data);

Options

interface EpubCheckOptions {
  /** EPUB version to validate against (auto-detected if not specified) */
  version?: '2.0' | '3.0' | '3.1' | '3.2' | '3.3';
  
  /** Validation profile */
  profile?: 'default' | 'edupub' | 'idx' | 'dict' | 'preview';
  
  /** Include usage messages in results (default: false) */
  includeUsage?: boolean;
  
  /** Include info messages in results (default: true) */
  includeInfo?: boolean;
  
  /** Maximum errors before stopping, 0 = unlimited (default: 0) */
  maxErrors?: number;
  
  /** Locale for messages (default: 'en') */
  locale?: string;
  
  /** Custom message severity overrides (message ID → severity) */
  customMessages?: Map<string, MessageSeverity>;
}

Result

interface EpubCheckResult {
  /** Whether the EPUB is valid (no errors or fatal errors) */
  valid: boolean;
  
  /** All validation messages */
  messages: ValidationMessage[];
  
  /** Counts by severity */
  fatalCount: number;
  errorCount: number;
  warningCount: number;
  infoCount: number;
  usageCount: number;
  
  /** Detected EPUB version */
  version?: string;
  
  /** Validation time in milliseconds */
  elapsedMs: number;
}

interface ValidationMessage {
  /** Unique message identifier (e.g., 'OPF-001') */
  id: string;
  
  /** Severity level */
  severity: 'fatal' | 'error' | 'warning' | 'info' | 'usage';
  
  /** Human-readable message */
  message: string;
  
  /** Location in the EPUB */
  location?: {
    path: string;
    line?: number;
    column?: number;
    context?: string;
  };
  
  /** Suggestion for fixing the issue */
  suggestion?: string;
}

JSON Report

Generate a JSON report compatible with the original EPUBCheck:

import { EpubCheck, Report } from '@likecoin/epubcheck-ts';

const result = await EpubCheck.validate(data);
const jsonReport = Report.toJSON(result);
console.log(jsonReport);

Supported Environments

Environment	Version	Notes
Node.js	18+	Full support
Chrome	89+	Full support
Firefox	89+	Full support
Safari	15+	Full support
Edge	89+	Full support

Architecture

This library is a TypeScript port of the Java-based EPUBCheck tool maintained by the W3C. Key implementation details:

• XML Processing: Uses libxml2-wasm for XML parsing and schema validation (RelaxNG, XSD) via WebAssembly
• ZIP Handling: Uses fflate for fast, lightweight EPUB container processing
• CSS Validation: Uses css-tree for CSS parsing and validation
• Schematron rules: Hand-ported to TypeScript rather than evaluated from .sch files — there is no Schematron engine, so the three runtime dependencies above are the whole list

Validation Coverage

Component	Status	Completeness	Notes
OCF Container	🟢 Complete	~92%	ZIP structure, mimetype, container.xml, encryption.xml obfuscation
Package Document (OPF)	🟢 Complete	~92%	Metadata, manifest, spine, collections, Schematron-equivalent checks
Content Documents	🟢 Complete	~93%	XHTML structure, CSS url(), @import, SVG, entities, title, SSML, XML version
Navigation Document	🟢 Complete	~95%	Nav content model, landmarks, labels, reading order, hidden, nested-ol
Schema Validation	🟡 Partial	~55%	RelaxNG for OPF/container; XHTML/SVG disabled (libxml2 limitation)
CSS	🟡 Partial	~85%	@font-face, @import, url() extraction, position, forbidden properties, alt style tags
Cross-reference Validation	🟢 Complete	~92%	Reference tracking, fragments, fallbacks, remote resources, cross-document features
Accessibility Checks	🟢 Complete	~71%	12/17 ACC checks: table, image alt, hyperlink, MathML, SVG, epub:type, OPF metadata
Media Overlays	🟡 Partial	~70%	SMIL structure, timing, audio, OPF metadata, duration validation
Media Validation	🟡 Partial	~25%	Magic number checks (MED-004/OPF-029/PKG-022); deep format parsing planned

Legend: 🟢 Complete | 🟡 Partial | 🔴 Basic | ❌ Not Started

The percentages above are per-component estimates. For what actually matters — whether this tool and Java EPUBCheck reach the same verdict on the same file — see the measured figures in PROJECT_STATUS.md: 97% valid/invalid agreement and 88% error/warning agreement across 758 fixtures, with the remaining differences enumerated.

Development

Prerequisites

• Node.js 18+
• npm 9+

Setup

# Clone the repository
git clone https://github.com/likecoin/epubcheck-ts.git
cd epubcheck-ts

# Install dependencies
npm install

# Run tests
npm test

# Build
npm run build

Scripts

Script	Description
npm run build	Build the library (ESM + CJS)
npm run dev	Build in watch mode
npm test	Run tests in watch mode
npm run test:run	Run tests once
npm run test:coverage	Run tests with coverage
npm run lint	Lint with ESLint
npm run lint:fix	Lint and auto-fix
npm run format	Format with Biome
npm run typecheck	TypeScript type checking
npm run check	Run all checks (format + typecheck)
npm run docs	Generate API docs (HTML + Markdown)
npm run docs:html	Generate HTML API docs to docs/html/
npm run docs:md	Generate Markdown API docs to docs/md/

Project Structure

epubcheck-ts/
├── src/
│   ├── index.ts           # Public API exports
│   ├── checker.ts         # Main EpubCheck class
│   ├── types.ts           # TypeScript type definitions
│   ├── core/              # Core validation logic
│   ├── ocf/               # OCF container validation ✅
│   ├── opf/               # Package document validation ✅
│   ├── content/           # Content document validation ✅
│   ├── nav/               # Navigation validation ✅
│   ├── ncx/               # NCX validation (EPUB 2) ✅
│   ├── references/        # Cross-reference validation ✅
│   ├── schema/            # Schema validation ✅
│   │   ├── relaxng.ts     # RelaxNG validation
│   │   ├── xsd.ts         # XSD validation
│   │   └── orchestrator.ts # Schema orchestration
│   └── messages/          # Error messages
├── schemas/               # Schema files (RNG, RNC, XSD)
├── test/
│   ├── fixtures/          # Test EPUB files
│   └── integration/       # Integration tests
├── docs/
│   └── md/                # Generated API docs (Markdown, checked in)
├── examples/
│   └── web/               # Web demo ✅
└── dist/                  # Build output

Legend: ✅ Implemented

Comparison with Java EPUBCheck

Aspect	epubcheck-ts	EPUBCheck (Java)
Runtime	Node.js / Browser	JVM
Verdict agreement	97% (measured, n=758)	Baseline
Bundle Size	~450KB JS + ~1.6MB WASM	~15MB
Installation	npm install	Download JAR
Integration	Native JS/TS	CLI or Java API
Performance	Comparable	Baseline

See PROJECT_STATUS.md for detailed feature comparison.

Contributing

Contributions are welcome! Please read CONTRIBUTING.md for guidelines.

For AI agents contributing to this project, see AGENTS.md.

License

BSD-3-Clause — the same license as the Java EPUBCheck. Releases up to and including 0.6.5 were published under GPL-3.0; 0.7.0 is the first BSD-3-Clause release.

This is an independent TypeScript implementation of the Java EPUBCheck: the validation logic is written from scratch, not translated line by line. The RELAX NG schemas, the message identifiers and their wording, and the test fixtures do come from the original project — along with the Nu Html Checker (MIT) and W3C MathML/SVG schemas it bundles. THIRD_PARTY_NOTICES.md reproduces the notices those require, and ships with the package.

Acknowledgments

• W3C EPUBCheck - The original Java implementation
• DAISY Consortium - Maintainers of EPUBCheck
• libxml2-wasm - WebAssembly XML processing

Built by 3ook.com

This project is built and maintained by the 3ook.com team. 3ook is a Web3 eBook platform where authors can publish EPUB ebooks and readers can collect them as digital assets. If you're an author looking to publish your ebook, check out 3ook.com.

Related Projects

• EPUBCheck - Official Java validator
• epub.js - EPUB reader library
• r2-shared-js - Readium shared models