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What is a .msg file?

A file ending in .msg is a single email saved by Microsoft Outlook. It is not plain text — it is a MAPI compound file, a small structured container that bundles the message body, the full headers (sender, recipients, date, subject), and any attachments into one file. Because the format is Outlook's own, double-clicking a .msg on a machine without Outlook usually does nothing useful. This page explains what is inside a .msg, why it behaves that way, and how to open it for free.

Open your .msg now →

Open a .msg file in 3 steps

1. Open MSGViewGo to msgview.app in any modern browser — Windows, Mac, Linux, ChromeOS, iOS or Android. There is nothing to install and no sign-up.
2. Drop your .msg fileDrag the file onto the page. It is parsed inside your browser tab and never uploaded — you can confirm that in your browser's Network panel.
3. Read the emailSee the sender, recipients (including Bcc), date, body and attachments. Save attachments or convert the message to PDF, HTML, EML or plain text.

What is actually inside a .msg file?

A .msg uses the Microsoft Compound File Binary format — essentially a tiny file system packed into one file. Inside it, Outlook stores a set of MAPI properties: the display name and address of the sender, the To, Cc and Bcc recipients, the sent and received timestamps, the subject line, and the message body in both plain-text and HTML form. Attachments are embedded as separate streams, and a single .msg can even contain other emails nested inside it — for example a forwarded message carried as an attachment. Because everything travels together in one file, a .msg is a faithful, self-contained snapshot of one email exactly as it looked in Outlook.

Sometimes the attachment you were expecting shows up as a mysterious winmail.dat instead. That is TNEF — another Outlook-specific wrapper. MSGView decodes TNEF and winmail.dat too, so the real attachments and formatting are recovered rather than lost.

Why does a .msg only open in Outlook?

Unlike the open .eml format that most email clients use, .msg is proprietary to Outlook. Windows associates the extension with Outlook, so on a computer that has it, a double-click opens the message. On a Mac, a Linux box, a Chromebook, or a phone — or a Windows PC without the desktop Outlook — nothing is registered to read the compound-file structure, so the file appears unopenable or opens as garbled binary. That is the single most common reason people go looking for what a .msg file is: they received one and their computer will not show it.

MSGView solves this by parsing the MAPI structure itself, in JavaScript, right in the browser tab. It handles CJK, Cyrillic and other character encodings correctly, so international messages read the way they were written. Files up to 100 MB are supported, which comfortably covers emails with large attachments.

Private by design

Because a .msg often contains confidential correspondence, privacy matters. MSGView reads the file entirely inside your browser — the parsing runs on your own device and nothing is ever sent to a server. There are no accounts, no cloud storage, no watermark, and no upload. You can verify this yourself: open your browser's Network panel and watch as you drop a file — no request goes out. The email you are reading stays on your machine.

FAQ

Related guides

• Open .msg without OutlookRead Outlook emails on any device — no Outlook install required.
• Convert .msg to EMLTurn Outlook's format into open .eml that any mail client can read.
• Extract .msg attachmentsPull every attachment out of a .msg and save them as a .zip.
• Open winmail.datDecode the mysterious TNEF attachment and recover the real files.

Open MSGView — free & private →