WKN Validation in Node.js

1. What is a WKN?

A WKN (Wertpapierkennnummer — also written WPKN or WPK) is a 6-character alphanumeric identifier assigned to securities traded in Germany. It has been used since 1968 and is issued by WM Datenservice (formerly Wertpapier-Mitteilungen), the Frankfurt-based financial data provider that acts as the National Numbering Agency (NNA) for German securities under ISO 6166.

WKNs appear in German brokerage confirmations, bank statements, and legacy trading systems. While ISINs have become the standard in cross-border and regulatory contexts (MiFID II, EMIR), WKNs remain widely used in the German retail and private banking segment. Many German financial APIs and data feeds still expose WKNs alongside or instead of ISINs.

Unlike ISIN, CUSIP, or SEDOL, the WKN has no check digit. It is a purely opaque sequence — there is no algorithm to verify whether a WKN is valid. The only way to confirm a WKN maps to a real security is to look it up in a reference database.

2. WKN anatomy

A WKN is exactly 6 characters long and consists of digits and uppercase letters:

Some well-known examples:

3. WKN inside a German ISIN

German ISINs (country code DE) embed the WKN in a predictable way. The NSIN (National Securities Identifying Number) portion of a German ISIN is the WKN zero-padded on the left to 9 characters:

For Deutsche Bank (WKN 514000):

DE  +  000514000  +  8  =  DE0005140008
┌──┐   ┌───┐┌──┐   ┌┐
│DE│   │000││514000│ │8│   ← ISIN check digit (Luhn over expanded string)
└──┘   └───┘└──────┘ └┘
  ↑        ↑
country   WKN zero-padded to 9 chars

You can extract a WKN from a German ISIN by taking characters 5–10 (1-indexed): strip the leading zeros from the NSIN to recover the original WKN. If you already have a DE ISIN, pass it to /v0/isin instead of /v0/wkn.

4. Why format checks aren't enough

5. The right solution: one API call

The IsValid WKN API handles format validation and instrument lookup via OpenFIGI in a single GET /v0/wkn request. Because there is no check digit to compute, the value is entirely in the enrichment: confirming the WKN maps to a real security and surfacing its name, ISIN, exchange, and FIGI.

Get your free API key at isvalid.dev. The free tier includes 100 calls per day.

Full parameter reference and response schema: WKN Validation API docs →

6. Node.js code example

Using the @isvalid-dev/sdk package or the native fetch API (Node 18+).

// wknValidator.js
import { createClient } from '@isvalid-dev/sdk';

const iv = createClient({ apiKey: process.env.ISVALID_API_KEY });

// ── Example usage ─────────────────────────────────────────────────────────────

const result = await iv.wkn('514000');  // Deutsche Bank AG

if (!result.valid) {
  console.log('Invalid WKN: wrong format (must be 6 alphanumeric characters)');
} else {
  console.log(`WKN         : ${result.wkn}`);
  if (result.found) {
    console.log(`Name        : ${result.name}`);
    console.log(`ISIN        : ${result.isin}`);
    console.log(`Ticker      : ${result.ticker}`);
    console.log(`Exchange    : ${result.exchCode}`);
    console.log(`FIGI        : ${result.figi}`);
    console.log(`Sector      : ${result.marketSector}`);
  }
}

Expected output for 514000:

WKN         : 514000
Name        : Deutsche Bank AG
ISIN        : DE0005140008
Ticker      : DBK
Exchange    : GY
FIGI        : BBG000BC5588
Sector      : Equity

// routes/securities.js (Express)
app.get('/securities/validate-wkn', async (req, res) => {
  const { wkn } = req.query;

  if (!wkn) {
    return res.status(400).json({ error: 'Missing wkn parameter' });
  }

  let result;
  try {
    result = await validateWkn(wkn);
  } catch {
    return res.status(502).json({ error: 'WKN validation service unavailable' });
  }

  if (!result.valid) {
    return res.status(400).json({ error: 'Invalid WKN', wkn });
  }

  res.json({
    wkn: result.wkn,
    found: result.found ?? null,
    isin: result.isin ?? null,
    name: result.name ?? null,
    ticker: result.ticker ?? null,
    exchCode: result.exchCode ?? null,
    figi: result.figi ?? null,
  });
});

7. cURL example

Deutsche Bank AG:

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/wkn?value=514000"

SAP SE:

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/wkn?value=716460"

Invalid format — fewer than 6 characters:

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/wkn?value=5140"

8. Understanding the response

Response for a valid WKN found in OpenFIGI:

{
  "valid": true,
  "wkn": "514000",
  "found": true,
  "dataSource": "openfigi",
  "isin": "DE0005140008",
  "name": "Deutsche Bank AG",
  "ticker": "DBK",
  "exchCode": "GY",
  "securityType": "Common Stock",
  "marketSector": "Equity",
  "figi": "BBG000BC5588",
  "compositeFIGI": "BBG000BC5588"
}

Response for a valid WKN not found in OpenFIGI:

{
  "valid": true,
  "wkn": "514000",
  "found": false
}

Response for an invalid WKN:

{
  "valid": false
}

9. Edge cases to handle

10. Summary

For cross-referencing, see also:

• ISIN validation — ISINs embed WKNs for DE-prefixed codes
• SEDOL validation — the UK equivalent
• CUSIP validation — the North American equivalent
• WKN Validation in Python

Node.js integration notes

In a TypeScript codebase, define a branded type to prevent WKNs from being confused with other 6-character strings at compile time: type Wkn = string & { readonly __brand: 'Wkn' }. Validate at the system boundary — when the WKN enters your application from user input, an upstream API, or a file import — and carry the branded type through the rest of your pipeline.

WKN validation is particularly relevant in German banking integrations: online brokerage order entry, portfolio management dashboards, and wealth management reporting tools. If your application accepts WKNs from users, the absence of a check digit means any plausible-looking 6-character string passes format validation. Pair the API call with client-side pattern matching (/^[A-Z0-9]{6}$/i) for instant UI feedback, and confirm against OpenFIGI on submission.

• Assert process.env.ISVALID_API_KEY at server startup, not lazily at first request
• Use Promise.allSettled() for batch WKN validation — it collects all results without aborting on the first failure
• Log the full parsed API response alongside the raw WKN — the ISIN and FIGI returned are useful for downstream reconciliation
• If you need the full ISIN from a WKN, use the isin field from the response rather than constructing it manually