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What's a '.dat' file?

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Summary: DAT files are used by many different applications. To know what to do with a DAT file, you need to know what application created it.

I have a ".dat" file on my computer, and I'd like to open it up and see what's inside. What is a .dat file, and what application do I use to look at it?

In short: there's no way to tell.

The problem is that many applications use the file extension ".dat" to indicate a file that contains data.

But that's exactly all it tells us, and that's not enough.

The problem is that so many different programs use ".dat" that it really doesn't tell you anything about the file, what it contains, or what program it belongs to. There is no standard format, and there is no standard way to interpret the contents. ".dat" is only a name and nothing more.

So I'll be clear: there is no way to know how to open a .dat file unless you know what program created it. Period.

"... if you don't know what application created the file, there's no way to know how to open it."

A good example is that Yahoo Instant Messenger (YIM) apparently keeps it's message history in a file that ends in ".dat". The way Yahoo works, you can only open that .dat file using Yahoo Instant Messenger, and only of you are logged in to the account that created the file in the first place.

But if you don't know what application created the file, there's no way to know how to open it.

If you do know what application created the file, then it's likely only that application can be used to open it.

Article C2140 - July 28, 2004

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Recent Comments
41 Comments

Hey Leo, I received a .dat file through e-mail from a Immo-office, they told me it should be opened with Acrobat Reader, but it doesn't seem to work. I replied them with telling them that I couldn't open it and then they just sent it again.
Could you please help me?
Thank you very much

Posted by: Raf at October 11, 2005 2:16 AM

An acrobat reader file is a ".pdf" file ... I've not heard of them using ".dat". Either the sender is doing something wrong, or their mail program is. Ask them to either send their mail as "plain text" with the attachment, or if they have some other way to get you the file.

Posted by: Leo at October 11, 2005 9:41 AM

Can u please tell me how to open an yahoo archived message that says dat file. and the symbol is in media player type....i have tried everything and they all say it does not support that kind of file. Need help fast. Please do the needful action in this regard reply me sooon

Thanks

Posted by: Kid at October 12, 2005 5:09 AM

You need to open a Yahoo Messenger .dat file using Yahoo Messenger logged into the same account that created the .dat file.

Posted by: Leo at October 12, 2005 9:55 AM

I'm closing comments on this article because the comments are all the same, and are all answered in the article. I've reworked the article to be more clear, please be sure to read it.

Posted by: Leo at October 13, 2005 10:41 AM

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