XRechnung
Open and read an XRechnung – free, no install
An XRechnung is an XML file, so opening it shows source code. This page reads a short summary and does not store the file. The summary is not the invoice you archive.
XRechnung is the German CIUS of EN 16931. It uses two syntaxes: UBL (Invoice or CreditNote) and UN/CEFACT CII (CrossIndustryInvoice). The checker shows the same summary after a validation, plus the rule codes.
Upload the XML here. The response has seller, buyer, invoice number, date, line items, totals, and the buyer reference (BT-10). On invoices to German public authorities that reference is often the Leitweg-ID. This form displays it and does not check it. See Leitweg-ID.
Other free options
KoSIT publishes the XRechnung visualization (GitHub mirror itplr-kosit/xrechnung-visualization, Apache 2.0). Those are XSLT building blocks, not a website we run: UBL or CII to an intermediate XML, then HTML or PDF. KoSIT says the components are optional, and a generated view is not a valid XRechnung and is not for archiving. This site does not run those stylesheets.
Mein ELSTER offers a free e-invoice viewer: E-Rechnung ansehen. The page says you can view your e-invoice there. The file field accepts .xml and .pdf, and the XRechnung and ZUGFeRD previews are switched on. ELSTER says it uses the current XRechnung version 3.0.1 and calls the service non-binding. The file field is on the page without a sign-in step. Login and account creation are only in the site header. The viewer displays the invoice. The page does not describe a check against the KoSIT rules. Here you upload with no account, and the checker validates the file with the KoSIT validator and shows the rule codes.
Questions
Mac or phone?
The file opens as XML source. This page shows the short summary in the browser, including on a phone, with no install.
Excel?
Excel does not understand UBL or CII as an invoice.
Make a PDF?
This page does not. A ZUGFeRD or Factur-X file is a PDF that already contains the XML. Check that on the ZUGFeRD page.