OpenP7M reads PDFs inside P7M files and supported FatturaPA XML right in the browser, and the page says document content stays on your device during processing. A full watermarked preview is free with no account, and exporting a single source file without the watermark costs EUR 1.99. Limits are 50 MB per file and 50 files or 100 MB per batch, and batches need an account. Local integrity checks do not validate certificate trust, revocation or legal signature validity.
I needed a simple way to inspect Italian P7M documents and electronic invoices in a browser without installing desktop software. OpenP7M keeps document processing local and makes the preview and export limits clear.