thelawin.dev Client Libraries

Official client libraries for the thelawin.dev ZUGFeRD/Factur-X E-Invoicing API.

Generate EU-compliant e-invoices with a simple, consistent API across all languages.

Available SDKs

Language	Package	Install
TypeScript/JavaScript	@thelawin/sdk	`npm install github:steviee/thelawin-clients#path:typescript`
Python	thelawin	`pip install git+https://github.com/steviee/thelawin-clients.git#subdirectory=python`
Ruby	thelawin	`gem install thelawin` (RubyGems)
Kotlin	dev.thelawin:sdk	JitPack or local build
Java	dev.thelawin:sdk	JitPack or local build
Swift	Thelawin	SPM: `https://github.com/steviee/thelawin-clients.git`
Dart	thelawin	Git dependency (see dart/README)
C#	Thelawin	Local build or Git submodule

Quick Start

All SDKs share the same fluent API design:

// JavaScript/TypeScript
import { ThelawinClient } from '@thelawin/sdk';

const client = new ThelawinClient('env_sandbox_demo');

const result = await client.invoice()
  .number('2026-001')
  .date('2026-01-15')
  .format('zugferd')
  .seller({ name: 'Acme GmbH', vatId: 'DE123456789', city: 'Berlin', country: 'DE' })
  .buyer({ name: 'Customer AG', city: 'Munich', country: 'DE' })
  .addItem({ description: 'Consulting', quantity: 8, unit: 'HUR', unitPrice: 150 })
  .template('minimal')
  .generate();

if (result.success) {
  result.downloadPdf();  // Browser: triggers download
} else {
  result.errors.forEach(e => console.error(`${e.path}: ${e.message}`));
}

Features

9 Formats - ZUGFeRD, Factur-X, XRechnung, Peppol, FatturaPA, UBL, CII, PDF
Fluent Builder API - Chain methods to build invoices
Retrieve - Extract invoice data from existing PDFs/XMLs
Logo Support - Load logos from files or URLs (auto Base64 encoding)
Error Handling - Detailed validation errors with JSON paths
Type Safety - Full TypeScript/type hint support
Browser + Server - Works in browsers and server environments

API Key

Get your API key at thelawin.dev/signup

Demo key (env_sandbox_demo): Free, no account needed, watermarked
Sandbox keys (env_sandbox_*): Free, 100 credits/month, watermarked
Live keys (env_live_*): Production use, requires paid plan

Documentation

Contributing

See CONTRIBUTING.md for guidelines.

License

MIT License - see LICENSE for details.

thelawin

Development

Runtime