Official SDKs

thelawin.dev provides official client libraries for 8 programming languages.

Every SDK shares the same shape, so switching languages later doesn't mean relearning the API:

• Fluent builder: chain methods to assemble an invoice
• Full type definitions and autocomplete
• Covers all nine output formats (ZUGFeRD, Factur-X, XRechnung, Peppol, FatturaPA, UBL, CII, PDF, plus auto)
• Retrieve: pull structured data back out of an existing PDF or XML
• Logo helpers: pass a file path, the SDK handles Base64 for you
• Result objects with explicit success / errors, no exceptions on validation failures
• 388 tests across the 8 SDKs (breakdown in the table below)

Installation

Language	Install	Status
TypeScript	npm install github:steviee/thelawin-clients#path:typescript	✅ GitHub
Python	pip install git+https://github.com/steviee/thelawin-clients.git#subdirectory=python	✅ GitHub
Ruby	gem install thelawin	✅ RubyGems
Kotlin	JitPack or local build	✅ GitHub
Java	JitPack or local build	✅ GitHub
Swift	https://github.com/steviee/thelawin-clients.git (SPM)	✅ GitHub
Dart	Git dependency (see Dart docs)	✅ GitHub
C#	Local build or Git submodule	✅ GitHub

Package Registries

Ruby is on RubyGems. All other SDKs install from GitHub. Publication on npm, PyPI, Maven Central, NuGet, and pub.dev follows with the stable release (#102).

Unified Interface

All SDKs follow the same pattern:

client = ThelawinClient(api_key)

result = client.invoice()
  .number("2026-001")
  .date("2026-01-15")
  .seller(name: "Acme GmbH", vat_id: "DE123456789", ...)
  .buyer(name: "Customer AG", ...)
  .addItem(description: "Consulting", quantity: 8, unit: "HUR", unit_price: 150)
  .logoFile("./logo.png")  // Auto Base64 encoding
  .template("minimal")
  .generate()

if result.success:
    result.savePdf("./invoice.pdf")
else:
    for error in result.errors:
        print(f"{error.path}: {error.message}")

Feature Comparison

Feature	TS	Python	Ruby	Kotlin	Java	Swift	Dart	C#
/v1/generate	✅	✅	✅	✅	✅	✅	✅	✅
/v1/validate	✅	✅	✅	✅	✅	✅	✅	✅
/v1/retrieve	✅	✅	✅	✅	✅	✅	✅	✅
/v1/account	✅	✅	✅	✅	✅	✅	✅	✅
Async/Await	✅	✅	-	✅	-	✅	✅	✅
Type Safety	✅	✅	✅	✅	✅	✅	✅	✅
Logo from File	✅	✅	✅	✅	✅	✅	✅	✅
Browser Support	✅	-	-	-	-	-	-	-
Tests	57	52	57	39	47	49	39	48

Source Code

All SDKs are open source and available on GitHub:

github.com/steviee/thelawin-clients

git clone https://github.com/steviee/thelawin-clients.git

Next Steps

Choose your language:

• TypeScript - For Node.js and browser applications
• Python - For Python projects
• Ruby - For Ruby on Rails and Ruby projects
• Kotlin - For Kotlin/JVM projects
• Java - For Java projects
• Swift - For iOS, macOS, and server-side Swift
• Dart - For Flutter and Dart projects
• C# - For .NET projects