jasy

ZUGFeRD & XRechnung e-invoices in pure TypeScript - generate, validate, read.
A Flutter-style PDF engine underneath. The EN-16931 maths done for you. Zero Java, zero upload.

npm i @jasy/zugferd  ·  npx @jasy/cli  ·  MIT

---

Don't believe us. Point it at your own invoice.

npx @jasy/cli validate ./your-invoice.pdf

That ✓ is the same official KoSIT Schematron + veraPDF the big players run - against the EN 16931 and the German XRechnung (BR-DE) rules, plus PDF/A-3. Your file, your terminal, in seconds. No account, no upload, nothing leaves your machine.

Java has Mustang. PHP has horstoeko. Python has factur-x.
Node had nothing. Now it has jasy.

---

You bring the line items. jasy does the rest.

You never compute a total, a VAT breakdown or a rounding again. You hand jasy the line items - it derives the document totals and the EN-16931 VAT breakdown, spec-correct. That is why the invoices validate: the amounts are correct by construction, so the single biggest class of EN-16931 failures (the BR-CO total checks) simply cannot happen.

import { renderZugferd } from "@jasy/zugferd";

const { bytes, xml } = await renderZugferd({
  number: "RE-2026-001",
  issueDate: "2026-06-17",
  currency: "EUR",
  seller: {
    name: "Northwind Studio GmbH",
    vatId: "DE123456789",
    address: { city: "Berlin", postCode: "10115", country: "DE" },
  },
  buyer: {
    name: "Globex Corporation Ltd",
    address: { city: "Munich", postCode: "80331", country: "DE" },
  },
  lines: [
    {
      name: "Brand identity design",
      quantity: 2,
      unit: "HUR",
      netUnitPrice: 100,
      vat: { category: "S", ratePercent: 19 },
    },
  ],
});
// bytes -> a valid ZUGFeRD PDF/A-3   ·   xml -> the embedded EN-16931 XML
// totals, tax breakdown and rounding: computed for you.

One object in. A conformant, human-readable PDF/A-3 and the EN-16931 CII/UBL XML out. ZUGFeRD and XRechnung work out of the box - no config, no template wrangling.

---

The whole loop, from the terminal

jasy read invoice.pdf               # identify + show: parties, line items, totals
jasy validate invoice.pdf           # EN 16931 + XRechnung + PDF/A (exit 1 if invalid)
jasy export invoice.pdf -o out.xlsx # read it back: JSON · TXT · Excel

Reads CII and UBL, real third-party invoices included - not just our own output.

---

A PDF engine that reads like Flutter

Underneath it all is a declarative, component-based PDF engine - written from the byte stream up, no headless browser, no pdf-lib. You describe the document; it lays it out and paginates.

import { Document, Page, Column, Text, renderToBytes } from "@jasy/pdf";

const pdf = await renderToBytes(
  Document([
    Page({ size: "A4", margin: 48 }, [
      Column({ gap: 8 }, [
        Text("Invoice RE-2026-001", { size: 24, bold: true, color: "steelblue" }),
        Text("Thank you for your business.", { color: "gray" }),
      ]),
    ]),
  ]),
);

Real text layout (Adobe AFM metrics, kerning, word-wrap), flexbox-style gap / justify / align, boxes with radius and alpha, images, custom TrueType fonts, AES-256 password encryption, and real pagination - content that overflows flows onto the next page, headers and footers repeat.

---

Under the hood - and every bit is real

This is not a wrapper around someone else's renderer. It is built from the byte stream up, and you can verify all of it:

• Hand-rolled PDF writer. No pdf-lib, no PDFKit, no Java, no headless Chrome - the byte stream is ours.
• Font subsetting. Only the glyphs you actually use are embedded, with the PDF/A subset tag - a 740 KB font ships as a ~76 KB subset, and the text stays copy- and searchable.
• Compression. Content streams and images are FlateDecode-compressed; the spreadsheets jasy export writes are real .xlsx ZIPs we deflate with our own writer and CRC32, zero dependencies.
• AES-256 encryption, pure JS. Lock a PDF with renderToBytes(doc, { encrypt: { userPassword } }) - the newest standard handler (AES-256, R6 / ISO 32000-2) via the platform WebCrypto: no native crypto, no deps, the same code in Node and the browser. Owner password + permissions optional.
• Real font metrics. Text is laid out with the Adobe AFM metrics of the standard-14 fonts - kerning and word-wrap are computed, not guessed.
• PDF/A-3, matched not approximated. The conformance graph is hand-built and passes veraPDF, the official ISO 19005 validator.
• Byte-exact round-trips. Generate and parse are inverses: generate → parse → regenerate reproduces the identical XML. 307 tests hold the line.
• Schematron, local. The official EN-16931 + XRechnung rules run via saxon-js (the real XSLT, in pure JS) - no Java, no upload.

---

Packages

Package	What it is
@jasy/zugferd	ZUGFeRD / XRechnung: your data → PDF/A-3 + EN-16931 XML, with local validation. The prize.
@jasy/cli	the jasy terminal: read · validate · export, headless and interactive
@jasy/pdf	the declarative, Flutter-style PDF layout engine that powers them

---

Why you can trust it

• 307 tests, green. The generator and the parser are byte-exact inverses: generate → parse → regenerate reproduces the identical XML. Nothing is silently lost.
• The same rules the authorities use - the official KoSIT EN-16931 + XRechnung Schematron, and the official veraPDF for the full ISO 19005 (PDF/A) check.
• Proven on real third-party invoices, not only our own.
• 100% local. No upload, no service, no account - DSGVO-safe by construction.

---

Honest scope

jasy targets the documents that matter here: invoices, reports, quotes, datasheets. It is not a LaTeX / WeasyPrint replacement - no microtypography, hyphenation or bidi, and arbitrary multi-page flow of any content is still maturing. For e-invoices (a table, totals, a footer) it is complete - they even paginate. We would rather under-promise and over-deliver in the demo above.

Status: young and pre-1.0. The API can still shift between minor versions. Everything shown here works and is tested.

---

MIT  ·  built by Florian Heuberger