---
title: ".dat file — what it is and how to open it"
description: "A .dat file is a Generic Data File. A meaningless extension — .dat says only that some program stored data here. How to open one on Windows, macOS and Linux, and what to convert it to."
url: https://atoneplace.net/file/dat/
site: "At One Place"
---

# .dat files

**.dat file: Generic Data File**

A meaningless extension — .dat says only that some program stored data here.

## What opens a .dat file

- **Windows:** The application that created it, Notepad (built in — to check if it is text), Winmail Opener (for winmail.dat)
- **macOS:** The application that created it, TextEdit (built in — to check if it is text), TNEF's Enough (for winmail.dat)
- **Linux:** The application that created it, file (to identify it), tnef (for winmail.dat)

## What a .dat file is

There is no such thing as "the DAT format". Programs use .dat for whatever internal data they like, so the right opener is always whichever application created it. The exception worth knowing is winmail.dat, which is an Outlook TNEF attachment produced when a sender's mail client uses Microsoft-only formatting — the tool winmail.dat readers or the site winmaildat.com extracts the real attachments from it.

## Details

- **Extension:** .dat
- **Full name:** Generic Data File
- **Category:** Data
- **Created by:** Various
- **Format:** Binary

## Common questions

### How do I open a .dat file?

On Windows use The application that created it; on macOS use The application that created it; on Linux use The application that created it. A meaningless extension — .dat says only that some program stored data here.

### What is a .dat file?

Generic Data File. There is no such thing as "the DAT format". Programs use .dat for whatever internal data they like, so the right opener is always whichever application created it.

## Related pages

- [.csv — Comma-Separated Values](https://atoneplace.net/file/csv/)
- [.json — JavaScript Object Notation](https://atoneplace.net/file/json/)
- [.xml — Extensible Markup Language](https://atoneplace.net/file/xml/)
- [.yaml — YAML Data File](https://atoneplace.net/file/yaml/)
- [.log — Log File](https://atoneplace.net/file/log/)
- [.torrent — BitTorrent Metainfo File](https://atoneplace.net/file/torrent/)
- [.vcf — vCard Contact File](https://atoneplace.net/file/vcf/)
- [.sql — SQL Script](https://atoneplace.net/file/sql/)
- [.ics — iCalendar Event](https://atoneplace.net/file/ics/)
- [.sqlite — SQLite Database](https://atoneplace.net/file/sqlite/)
- [.db — Generic Database File](https://atoneplace.net/file/db/)
- [.bin — Binary File](https://atoneplace.net/file/bin/)

## Sources

- Media Types Registry — IANA (https://www.iana.org/assignments/media-types/)
- Official vendor product documentation — At One Place (/about/)