How to Open DAT Files on a Mac

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Quick ways to access the contents of DAT files on a Mac computer
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DAT files are used by various programs to store text, graphics, video, or binary data. The most common DAT file you may encounter on a Mac is a malformed email attachment sent from Microsoft Outlook. These files usually come as winmail.dat or ATT0001.dat . Because DAT files have such broad functionality, it can be difficult to determine what program to use to open them. You can open DAT files in a text editor like TextEdit to determine what program to use, or use an app specifically for opening DAT files attached to emails. Read on to learn how to open them, with tips from computer specialist Yaffet Meshesha.

Opening DAT Files on Mac

Most DAT files contain plain text. To open them, right-click or Ctrl-click the file and select Open With > TextEdit . If the file contains something other than text, your Mac might suggest an alternative app, such as a media player. You can also try an app designed to open winmail.dat files, like TNEF’s Enough.

Section 1 of 7:

What is a DAT file?

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  1. 1
    These data files contain information related to the program that created them. DAT files, which end in a “.dat” extension, are generic data files that can be created by almost any computer program. [1] According to Meshesha, most of these files contain simple text. However, some may contain other types of data, such as images, video, or sound.
  2. 2
    You’re most likely to see DAT files as email attachments on Mac. While many programs on your Mac can generate .dat or .data files, you’ll typically encounter them as email attachments, often with the name “winmail.dat” or “ATT0001.dat.” This may happen if someone sends you an email message with an attachment that your computer or email app can’t read.
    • For example, this is a common error in Apple Mail, which has trouble interpreting files sent in Outlook’s proprietary TNEF format. [2]
    • This can also happen when someone sends you an email in RTF (Rich Text) format and your mail app can’t interpret it. In these cases, the DAT file may simply contain the text of the message they were trying to send you.
    • If you see one of these files attached to an email, don’t try to open it unless you trust the sender. If you do, ask them if they intended to send an attachment with their email. If not, ask them to send future messages in HTML or plain text instead of RTF format to prevent this from happening.
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  3. 3
    The right way to open the file depends on what kind of data it contains. Meshesha explains that most DAT files can be opened with a basic text editor like TextEdit or Notepad. However, if the .dat file contains some other type of data, such as an image or a video, you’ll need a different app to open it.
    • For example, some .dat files contain PDF data and can be opened with a program like Preview or Adobe Acrobat.
    • Your Mac may suggest an appropriate app for opening the file if you Ctrl -click or right-click it and select Open With .
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Section 2 of 7:

Opening DAT Files in TextEdit

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  1. Right-clicking or Ctrl -clicking a file will display a pop-up menu for that file.
    • If you are using an Apple Magic Mouse or a MacBook with a trackpad, you can right-click by clicking with two fingers on the trackpad or magic mouse.
    • You can use this method for most DAT files that contain plain text.
  2. This will display a list of applications that the file can be opened up with.
  3. TextEdit can read most text-based files on your computer. You may be able to read the text to ascertain what program the DAT file is used in or to read its contents to see if it was originally an email message formatted as RTF. If TextEdit cannot open the DAT file, it isn't a text-based file.
    • You probably won’t see TextEdit as an option if your DAT file doesn’t contain text. In these cases, you might see something like VLC, Preview, or QuickTime instead.
    • Some DAT files are locked and cannot be manipulated.
  4. DAT files have no set structure or layout and are often lines of code or instructions meant for a specific program. If you see mention of any software, there is a good chance that the DAT file was intended to be used with that program. Try opening the DAT with the program mentioned.
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Section 3 of 7:

Opening DAT Files in Excel

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  1. 1
    Open the file in a text editor first. Opening a DAT file in Excel can be useful if you need to visualize or manipulate the data in the file. Depending on how the data is formatted in the DAT file, exporting it into Excel or a similar spreadsheet app may be a pretty simple matter. To start, right-click or Ctrl-click the file and select Open With > Text Edit (or your text editor of choice).
    • This will work best if the data in the file is comma- or tab-separated. If the data isn’t already delineated this way, you might wish to do so manually before you try to import it.
    • Use this method for DAT files that contain text data.
  2. 2
    Copy the data to a new file if necessary. Some DAT files are locked so you can’t edit or duplicate them. In these cases, you may be unable to import the data from the original file to Excel since Excel may not recognize the file format. You can get around this by selecting the text in the file, copying it, and pasting it into a new text file in the same text editor. Give the new file a name you can easily recognize and save it to a convenient location on your Mac.
    • If you can do so, you can also select Duplicate or Save As from the File menu and simply save a copy of the DAT file as a text file.
  3. 3
    Open Excel. Once you’ve made any desired edits to the text in your DAT file, launch the Excel app.
  4. 4
    Click File > Import . Click File in the Excel menu bar at the top of the screen, then select the Import option.
  5. 5
    Select “Text file” and click Import . A window will open, prompting you to select a type of file to import. Click the radio button next to Text file and then click the Import button.
  6. 6
    Choose your file and click Get Data . A file browser will open. Locate the text file you created from the DAT file and click Get Data .
  7. 7
    Follow the prompts in the Text Import Wizard. This wizard will help ensure that your data is imported in a helpful way.
    • On the first page, select whether to import your data in “Delimited” format (e.g., as values separated by tabs or commas) or “Fixed width” (use this for data formatted as columns with spaces between them in the original document). You can also choose your starting row if you don’t want to import all the data from the DAT file. Click Next to continue.
    • Choose the right kind of delimiter for your data on the next page. For example, if your data is separated by commas in the text file, click the checkbox next to “Comma.” You can also choose “Other” if none of the default options match. Click Next .
    • Choose the column data format. For example, you can choose to import each column as general data, text, or a date. Click Finish .
  8. 8
    Choose how you want to view the data in Excel. Next, you’ll be prompted to import your data into an existing sheet or create a new sheet. This window may also allow you to change how the data is formatted (e.g., in a table, PivotTable, or PivotChart). Click Import when you’ve made your selections.
    • You can now view and manipulate the data from the DAT file in spreadsheet format.
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Section 4 of 7:

Opening Winmail.dat Files

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  1. Download an app that’s capable of opening DAT files. There are several apps that can open or extract DAT files. Try one of these popular options:
    • TNEF’s Enough : This app is specifically for opening winmail.dat files. It’s completely free to download and use.
    • Winmail Viewer - Letter Opener : In addition to winmail.dat files, this app can also open MSG and XPS files on your Mac. You can open a limited number of files each week for free, or pay a subscription fee to open unlimited files.
    • BetterZip : This is an archiving app that’s capable of extracting a wide variety of archive types, including winmail.dat. There’s a license fee of $24.95, but it may be worthwhile if you are interested in the app’s other features (such as creating, editing, and opening/extracting several kinds of archives ).
Section 5 of 7:

Opening DAT Files Online

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  1. Open your file in www.winmaildat.com . If you can’t or don’t want to download an app to your Mac, this website is a fast and free alternative. Visit www.winmaildat.com / in a browser and drag and drop the file you want to open into the Drop files here field. You can also click the browse files button to open a Finder window and upload the file that way. Click Start to begin the upload, then download the contents of the file once it’s finished processing.
    • In some cases, the winmail.dat file might not contain any actual files or attachments. If the file only contains data about things like the message’s fonts or formatting, you’ll see an empty results page after uploading your file. [3]
    • Winmail.dat files that are smaller than 20kb typically don’t contain any actual file attachments.
    • There’s also a companion desktop app if you’d rather not use the website.
    • Similar websites include www.winmaildat.de/en/ and www.winmail-dat.com/online.php .
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Section 6 of 7:

Opening DAT Files in Gmail

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  1. Forward emails with problematic attachments to Gmail. If you’ve gotten an email with a winmail.dat or ATT0001.dat attachment in your Mac’s mail app, you might be able to get around the issue by opening the message in Gmail instead. The Gmail web client can often handle attachments and messages that your computer can’t.
    • If you don’t already have a Gmail account, set one up now .
    • Forward the message with the DAT attachment to your Gmail address (or, if you’re already using a Gmail account in your desktop mail client, simply open the same message in the Gmail web client instead).
    • Go to https://mail.google.com and open the forwarded message. See if you can view the message and/or the problematic attachments.
Section 7 of 7:

Changing the File Extension

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  1. Try this method if you know what type of data the DAT file contains. In some cases, you can open a DAT file simply by changing the extension to the correct one for the file type. For example, this may work if your DAT file is actually an image or video that your computer isn’t interpreting correctly. If you’re trying to open a video file, for instance, try changing the extension to “.MP4”. Or, for a text file, change the extension to “.TXT”.
    • To change a file extension, click the file to select it, then click it again to highlight the file name. Select the “.dat” extension and type over it with the new extension.
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      References

      1. ↑ https://www.adobe.com/uk/acrobat/resources/document-files/data-files/dat.html
      2. ↑ https://mepis.org/community/t/how-can-i-open-a-winmail-dat-file-on-my-mac/1172/2
      3. ↑ https://www.winmaildat.com/about

      About This Article

      Article Summary X

      1. Right-click the file.
      2. Hover the cursor over Open With .
      3. Click TextEdit .

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