DAT File Documentation

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Technical details

Feature	Value
Full name	Data File (generic program data)
File extension	.dat
MIME type	application/octet-stream
Format type	Generic application data — opaque content defined by the producing app
Developer	N/A — a shared “data” suffix used by many unrelated programs
Introduced	1970s–1980s (predates DOS; used across CP/M, DOS, Unix)
Open standard	Partial — depends entirely on the writing program
Magic number	None generic — identify by origin and byte inspection
Content	Text (configs, logs, delimited exports) or serialized binary
Standard header	None shared across .dat files
How to identify	Hex/text editor, TrID, or the Unix file command
Named formats also using .dat	Outlook winmail.dat (TNEF), Video CD AVSEQ##.DAT, Minecraft level.dat, Windows NTUSER.DAT
Safe to delete	Depends — caches usually yes; saves and system hives no
Related extensions	.data, .bin, .tmp, .db

What is a DAT file?

.dat is short for “data”, and it has been a catch-all suffix since the CP/M, DOS and Unix era of the 1970s and 1980s. Unlike a real format it makes no promise about content. A .dat may be plain text, serialized binary, a small embedded database, a cache or a save file. The same three letters are written by countless unrelated programs, each defining its own private layout, so the first task with any .dat is identification, not opening. There is no shared header, no shared magic number, and no universal “DAT converter”.

This matters because the most common mistake users make is treating .dat as a single thing. A game’s settings .dat, a browser cache .dat, an exported instrument reading and a Windows registry hive all end in .dat and have nothing in common beyond the label.

Text or binary: reading the first bytes

Every .dat falls into one of two broad camps, and a quick look at its first bytes tells you which. Open the file in a plain-text editor such as Notepad++ or TextEdit. If you see readable characters, words, numbers or delimited columns, it is a text .dat: a configuration file, a log, or a delimited export you can often read directly or import into a spreadsheet. If you see rows of unprintable symbols, it is a binary .dat, serialized data meant only for the program that wrote it.

For binary files, a hex editor sharpens the guess, because many real formats leave a recognisable signature in their first few bytes even when hidden behind a .dat name:

First bytes (hex)   Likely real format
1F 8B               gzip-compressed data
50 4B 03 04         ZIP archive (or a ZIP-based format)
89 50 4E 47         PNG image
25 50 44 46         PDF document
7B (ASCII '{')      JSON or other text

This is inspection, not execution: opening a .dat in a text or hex editor never runs its contents, so it is safe even for an untrusted file.

The identify-first workflow

Because the content is arbitrary, the dependable approach is to identify before doing anything else. First, note where the file came from: the folder it sits in, the sibling files around it, and the app or device that produced it usually reveal the owner (a program’s name is often in the parent directory). Second, inspect the bytes as above. Third, for a binary file whose signature you do not recognise, run a signature identifier. The Unix file command (file unknown.dat) reports the actual content type; TrID and FileAlyzer do the same on Windows by matching against a database of known headers. Once you know the true format, you open it with the matching program, or, if the extension is simply wrong, rename a copy to the correct one.

Why renaming a .dat converts nothing

A frequent expectation is that renaming file.dat to file.jpg, file.mp3 or file.docx will make it open. Renaming changes only the label the operating system uses to pick a default app; it does not alter a single byte of content. It helps in exactly one case: when the file already is that format and merely has the wrong extension, which you can only know after inspecting it. If a .dat is genuinely binary application data, no rename and no generic converter will turn it into a usable document; it must go back through the program that created it, which can export to a standard format.

When a .dat turns out to be a real format

Some well-known files use .dat but are really specific, documented formats, and they are handled as distinct types rather than generic data. Outlook’s winmail.dat is a Microsoft TNEF wrapper (signature 78 9F 3E 22, little-endian) that hides real e-mail attachments and needs a TNEF extractor. A Video CD stores its video as AVSEQ##.DAT files, which are MPEG-1 streams that play directly in a media player such as VLC. Minecraft’s level.dat is a gzip-compressed NBT world file, and Windows’ NTUSER.DAT is the per-user registry hive, which must never be deleted. In each case the file is really that format; the .dat name is incidental.

Is a DAT file safe, and can I delete it?

A generic .dat is opaque, so treat unexpected ones with the same caution as any unknown download: malware occasionally stores its payload or configuration as a .dat to look innocuous. Inspecting one in a hex or text editor is safe because it does not execute the file, but do not assume renaming makes it safe or usable, and avoid uploading potentially confidential .dat files to online converters. Whether it is safe to delete depends on the owner: app caches usually regenerate and are safe to remove, but a program’s save or data file may be important, and system .dat files such as NTUSER.DAT must be left alone. Identify the owner before deleting.

References

• file(1) — Unix file type identification utility
• TrID — file identifier with signature database
• FileAlyzer — file analysis tool

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