Open a .p7m file on Windows 10 and 11

Quick answer

1. Open this page in Edge (preinstalled on Windows 10 and 11) or Chrome.
2. Drag the .p7m from File Explorer — or straight from an Outlook message — onto the box above.
3. Press Download. The original document lands in your Downloads folder (Ctrl+J shows it in both browsers) and opens with your usual PDF, Word or Excel app.

Want double-click instead? Install ApriP7M as a web app and choose it under Open with — steps below. Both routes are free for one file at a time.

Why Windows cannot open .p7m files

A .p7m is a CAdES-signed envelope, the format Italian companies, accountants and public offices use for signed contracts and e-invoices (the general background is in How to open a .p7m file). Windows ships no program that understands it, so a double-click only brings up the dialog asking which app should open the file. Picking an app at random does not help: Notepad shows binary noise with scraps of readable text, and a PDF reader refuses the file because it begins with signature data rather than a PDF header.

The usual fixes are desktop signature programs from Italian certificate authorities or viewers from the Microsoft Store. They work, but they must be installed — and on a managed company laptop, installing software or using the Store is often blocked, or needs a ticket to IT. A browser tool avoids that entirely.

Method 1: drag and drop in Edge or Chrome

This works the same on Windows 10 and Windows 11, on personal and company PCs, and needs nothing beyond an up-to-date browser.

1. In File Explorer, find the file — usually in Downloads, or wherever your mail program saved it.
2. Drag it onto the box at the top of this page (or click the box and pick the file).
3. ApriP7M shows the name of the document inside, a preview, who signed it and the result of the integrity check: “Signature intact” or “Signature NOT intact”.
4. Press Download to save the enclosed file without the signature wrapper. For an Italian e-invoice (.xml.p7m) you instead see a readable invoice with English labels and can press Download PDF.

After the first visit the page also works offline, which is handy on a train or behind a strict corporate proxy.

Method 2: open .p7m files with a double-click

ApriP7M can be installed as a web app (a PWA). Once installed from Edge or Chrome, Windows treats it like any other program: it gets a Start menu entry and registers as a handler for .p7m, .m7m, .tsd and .xml files.

Install it

• Microsoft Edge: select the App available icon in the address bar, then Install. If the icon is not there, open Settings and more (…) › More tools › Apps and use the install entry for this site.
• Google Chrome: select Install at the right of the address bar, or open the ⋮ menu › Cast, save, and share › Install page as app…

Menu labels move around between browser versions; these are the ones on Microsoft’s and Google’s current help pages.

Use it from File Explorer

1. Right-click a .p7m file › Open with › ApriP7M.
2. The first time, the browser asks whether the app may open this file type. Confirm, and from then on the file opens straight in the app.
3. To make it permanent, choose Open with › Choose another app, select ApriP7M and tell Windows to always use it. Alternatively, go to Settings › Apps › Default apps, type .p7m in the search box under “Set a default for a file type or link type”, and pick ApriP7M.

Installing does not take over your ordinary .xml files: Windows does not let an app silently replace an existing default, so nothing changes until you choose. Two honest caveats: the installed app currently starts on ApriP7M’s Italian page (same layout as here: the result badge and the download button sit in the same places under the preview), and double-click association is only available through Edge or Chrome — Firefox users can still drag files onto this page. To remove the app: in Edge go to edge://apps › Details › Uninstall; in Chrome open the app’s ⋮ menu › Uninstall.

Attachments from Outlook and Italian PEC mail

• Classic Outlook: drag the attachment from the message straight onto the box. No need to save it first.
• New Outlook or Outlook on the web: if dragging does nothing, use the attachment’s menu to download it, then drop it from Downloads.
• The attachment is called smime.p7m: that is a whole S/MIME e-mail, not a signed document. See smime.p7m files for what to do in Outlook.
• Italian certified mail (PEC) opened in an ordinary mail program shows wrapper files — postacert.eml, daticert.xml, smime.p7s — instead of the attachments you expect. Save the message as .eml and drop it: ApriP7M opens the envelope and lists the real attachments, including any .p7m inside.

Locked-down work PC? What to tell IT

Using ApriP7M in the browser needs no administrator rights and writes nothing to the system. The web app install happens inside your own browser profile, so it normally works on a standard user account too — unless your organisation has disabled app installs through browser policy, in which case the install entry is missing and drag and drop remains available. Microsoft notes that web apps are not supported in FSLogix virtual-desktop environments: there the installed app disappears after you sign out, so just bookmark this page.

For a security review, the facts are short. The document is read with the browser’s File API and decoded by code that was already downloaded with the page. The page’s Content Security Policy sets connect-src 'none', so the browser itself refuses any network request while a file is being processed. You can verify it: press F12, open the Network tab, drop a file, and you will find no request that carries it (the only entries, if any, are the page’s own script files from aprip7m.com, loaded on demand) — or go offline once the page has loaded and see that it still works. No executable, no driver, no browser extension.

Turning it into a PDF on Windows

A .pdf.p7m already contains a PDF: Download gives it back unchanged. An Italian .xml.p7m invoice is data, not a layout, so use Download PDF for a courtesy copy, or Print / Save as PDF and pick “Microsoft Print to PDF” or “Save as PDF” as the printer. Every case, including openssl for scripts, is covered in P7M to PDF.

Many files at once

Free: one file at a time, with no daily limit and no account. If you select a whole batch in File Explorer (Ctrl+A) and drop it, the free plan opens the first and tells you about the rest. Pro (€19.99 one-time, VAT included, up to 3 devices, 14-day refund) opens dozens of files, a whole folder or a ZIP in one go — still on your PC — and exports a ZIP of PDFs plus an Excel / CSV register of the invoices.

What the check means

ApriP7M confirms that the content has not changed since it was signed and shows the signer’s certificate. That is an integrity check, not a qualified verification: it does not consult the EU or AgID trusted lists or revocation data, and it cannot say whether a document is legally valid. When that matters, use a qualified validation service such as Poste Italiane’s free Verificatore On Line, or the desktop software of an Italian certificate authority. ApriP7M is an independent service with no link to those providers.

If something goes wrong

• A file called contract.pdf will not open as a PDF — it may really be contract.pdf.p7m: once a program is registered for .p7m, Windows can hide that last extension, and the icon is that program’s rather than your PDF reader’s. Turn on file name extensions (Windows 11: File Explorer › View › Show › File name extensions; Windows 10: the View tab › File name extensions) to see the full name.
• ApriP7M is not listed under Open with — check that the install finished (it appears in the Start menu), then use Choose another app and scroll the list.
• “This does not look like a signed envelope” — the download was cut short or the file is something else. Save the attachment again from the e-mail.
• “Signature NOT intact” — the content no longer matches the signature. Ask the sender for a fresh copy before relying on it.