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Validate EN 16931 e-invoices: XRechnung, ZUGFeRD, Factur-X, Peppol BIS
Validate e-invoices (ZUGFeRD, Factur-X, XRechnung, Peppol BIS) and get a validation report.
invowerk API is a free Data Validation API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
invowerk API-Referenz: Endpunkte, Parameter und Beispiele, mit der maschinenlesbaren OpenAPI-Spezifikation unter /openapi.json.
Details from invowerk.dev.

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Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Validate EN 16931 e-invoices: XRechnung, ZUGFeRD, Factur-X, Peppol BIS
US address standardization, congressional and state legislative districts, Census data; free tier
The invowerk API is provided by invowerk (invowerk.dev). invowerk API-Referenz: Endpunkte, Parameter und Beispiele, mit der maschinenlesbaren OpenAPI-Spezifikation unter /openapi.json.
Yes. The invowerk API is listed in the Data Validation category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The invowerk API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the invowerk API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The invowerk API is served over HTTPS, so it's safe to use in production.