Is it safe to open confidential or legal PST files in OnlinePSTViewer.com?

Yes, 100%. OnlinePSTViewer.com operates on an air-gapped client-side model engineered by Prismmigration. When you select a file, the browser reads it directly into local memory using HTML5 File API and Web Workers. Zero file data, email content, or metadata is ever transmitted over the internet.

Can I open PST files on Mac, Linux, or Chromebook?

Yes! Because OnlinePSTViewer.com runs inside modern web browsers (Chrome, Edge, Safari, Firefox), you can open and read Outlook PST and OST files seamlessly on macOS, Linux, ChromeOS, iPad, and Windows without needing Microsoft Office or Outlook installed.

What is the difference between PST and OST files?

PST (Personal Storage Table) files are used by Microsoft Outlook for archiving and POP3 email accounts. OST (Offline Storage Table) files are cached local copies created by Exchange, Office 365, and IMAP accounts. OnlinePSTViewer.com parses both formats seamlessly.

Is there a file size limit for PST archives?

There are zero file size limits. OnlinePSTViewer.com utilizes client-side chunked byte slicing directly from your hard drive, meaning multi-gigabyte PST files of any size (50 GB, 100 GB+) open smoothly without overwhelming browser memory or uploading data to servers.

What is a winmail.dat file and why did I receive one?

A winmail.dat file is created when someone sends an email from Microsoft Outlook using Microsofts proprietary Rich Text Format (RTF) or Transport Neutral Encapsulation Format (TNEF). Non-Outlook email clients (like Apple Mail, Gmail, or Thunderbird) cannot read this format and package the formatted message and original attachments into a single file named winmail.dat.

How can I open a winmail.dat file on Mac, iPhone, or Android?

Simply drag and drop your winmail.dat file into OmniPST on Safari, Chrome, or any mobile browser. OmniPST decodes the binary TNEF stream locally in seconds and extracts all contained PDFs, images, and documents for instant download.

Is it safe to upload confidential winmail.dat files to OmniPST?

OmniPST does not upload your file anywhere! All TNEF unpacking is performed 100% inside your local web browser memory. Zero bytes leave your device.

100% Free • Private In-Browser Viewer

Free Online Winmail.dat Opener

Extract hidden PDF, Word, Excel, and image attachments from unreadable Microsoft Outlook winmail.dat files directly in your web browser. 100% free, private, and instant.

Drag & Drop your winmail.dat file here

Works on Mac, iPhone, iPad, Windows, Linux, and Android

No data sent to server (100% RAM)Extracts PDF, Word, Excel & PhotosWorks on Mac, iPhone, Android & PC

Why You Need OmniPST Winmail Opener

The fastest, most secure way to rescue trapped attachments from Microsoft Outlook TNEF encoding.

1. Unpack All Embedded Documents

Extracts PDFs, Word .docx, Excel .xlsx, PowerPoint .pptx, and images hidden inside the proprietary Microsoft TNEF wrapper.

2. Air-Gapped Privacy Guarantee

No business contract, financial sheet, or confidential invoice is ever uploaded to a server. 100% processed in local browser RAM.

3. Instant File Preview & Save

View extracted attachments directly in your browser or save them to your device with authentic original filenames.

4. Rich RTF & HTML Recovery

Reconstructs original Microsoft Rich Text formatting, sender signatures, tables, and colored text from corrupted messages.

5. macOS & Apple Mail Fix

Eliminates the dreaded unreadable winmail.dat file received on Mac, iPad, iPhone, and Android email apps with zero configuration.

6. Zero App Installation

No need to pay $39 for desktop extraction utilities or create accounts. Drop your file and get your documents in under 1 second.

Unrivaled Speed & Privacy

OmniPST vs Other Winmail Openers

Why privacy-conscious users and businesses avoid uploading confidential contracts to remote conversion sites.

Feature & Security Capabilities	OmniPST WinmailYou	Winmaildat.com (Remote)	Letter Opener ($39 App)
Zero Server Upload (100% In-Browser Privacy) Your attachments are extracted in browser RAM. Never transmitted over the internet.
No Desktop App Purchase Required Desktop tools like Letter Opener charge up to $39 for a basic license.
Extracts Hidden Documents, PDFs & Photos Unpacks all embedded TNEF binary objects into real downloadable files.
Reconstructs RTF Message Body & Text Recovers original email message text and sender styling.
Works on iOS, Android, Mac, Linux & Windows Runs in any modern browser without OS restrictions.
Zero Ad Walls or Waiting Queues Extract instantly without waiting for remote server conversion queues.
Pricing & Account Barrier Unrestricted attachment recovery without hidden paywalls.	100% Free & No Signup	Ad-heavy / Limits	$39+ Paid Software

How to Open Winmail.dat Files in 3 Steps

Works seamlessly on Mac, iPhone, iPad, Windows, and Chromebook

Upload Winmail.dat

Save the winmail.dat attachment from your email and drop it here.

Automatic Decompile

Our client-side engine strips the TNEF headers and isolates embedded documents.

Download Your Files

Click on the extracted PDFs, Word documents, or images to view and download.

Winmail.dat FAQs & Help

Frequently Asked Questions

Everything you need to know about extracting and opening winmail.dat attachments safely.

A winmail.dat file is generated when someone sends an email from Microsoft Outlook or Microsoft Exchange using Microsoft’s proprietary Transport Neutral Encapsulation Format (TNEF) or Rich Text Format (RTF). Non-Outlook email clients (such as Apple Mail on Mac/iPhone, Gmail, or Mozilla Thunderbird) cannot natively read TNEF, so they bundle the message body, formatting, and real attachments into a single file named winmail.dat.