Winmail.dat Opener
Open a winmail.dat attachment and extract the files inside it. Download individual files or a ZIP without Outlook or uploading your email data.
Drop your Winmail.dat file here
Find the attachments hidden inside winmail.dat.
.dat files up to 25 MB · No upload requiredOpening your email…
How to open winmail.dat and extract files
winmail.dat is commonly an Outlook TNEF container that packages message formatting and, sometimes, attached files. Save the container from your email first, then open it here to see which files it actually contains.
- Save the original winmail.dat attachment and select it above.
- Review the extracted filenames, file types and sizes.
- Download each needed file, or choose Download attachments ZIP to save them together.
Why did you receive a winmail.dat attachment?
Some Outlook messages carry rich-text formatting and other Outlook data in TNEF. A receiving mail application that does not interpret the container may show it as winmail.dat. The filename alone does not tell you whether it contains a document, images or only formatting information.
The opener focuses on extracting stored files. You do not need to rename the container to PDF, ZIP or another extension. If the sender intended to send a particular document but it is absent from the results, ask them to resend that document as an ordinary attachment.
What the extraction results mean
The tool checks container framing and attribute checksums before extraction. Those checks can identify damaged data, but they do not verify the sender or scan the extracted files for malware. An extracted file still needs the appropriate application to read its format.
| Result | What to do |
|---|---|
| One or more files | Check the names and sizes, then download the files you need. |
| No file attachments | The valid TNEF container may contain only formatting or body data. |
| Checksum or truncated-file error | Save the original attachment again; the stored data may be damaged. |
| Not a TNEF file | Use the application associated with that file rather than changing its extension. |
A winmail.dat example you can inspect
The built-in sample is a fictional TNEF container with a small text attachment. Open it with the sample button to see the attachment list and try an individual download or ZIP. The sample is for demonstrating extraction; it is not an email from a real sender.
Winmail.dat on Mac, Windows and Linux
Use the same browser workflow on any of these systems: save the attachment, open this page and select the saved file. Outlook is not required. The container is parsed on your device, with a maximum input size of 25 MB.
Extraction is limited to 1,000 files and 50 MB of decoded attachment data. Embedded messages and OLE objects may be offered as stored files, but are not opened or converted here. Encrypted content is not decrypted.
Other .dat files and files inside an EML
The .dat extension is used by many unrelated applications. This opener expects a TNEF file, identified by its internal structure, so it will not work as a general-purpose DAT viewer. Renaming an arbitrary data file to winmail.dat cannot change that structure.
If winmail.dat is attached to a saved EML email, use the EML attachment extractor to download it first. Open that extracted container here as the next step. The two tools handle separate layers: the email's MIME attachments and the files packaged inside TNEF.
Winmail.dat opener questions
Can I open winmail.dat on a Mac?
Yes. The tool runs in a modern browser on Mac, Windows or Linux. No Outlook installation is needed.
Why are there no attachments?
Some TNEF files contain only message formatting or body data. A valid container does not necessarily include attached files.
What if the file is damaged?
Invalid framing or a checksum mismatch produces an error. Save the original winmail.dat again, or ask for the attachments to be sent as ordinary files.
Can it open every embedded object?
Embedded messages and OLE objects may be extracted as stored files, but are not opened or converted here. Encrypted content is not decrypted. Downloading a file does not establish that it is safe.
Does my data leave my device?
Your selected files and pasted text are processed in your browser, without being uploaded to EMLKit. Remove the input or leave the page to clear the current workspace. Ordinary page requests still reach the site host. Read about file handling.