A DAT file is a generic container that holds data in whatever format the program that created it decided to use
DAT stands for "data," which is not very helpful because almost every file on your computer contains data. The real point is that DAT is a catch-all extension — when a software maker doesn't want to use a specific file type like .txt or .jpg, they often use .dat instead. This means a DAT file could contain text, images, settings, video, or anything else. You cannot tell what is inside just by looking at the extension.
Most DAT files are created by programs you have installed, and they are meant to stay hidden in your system folders. You will rarely need to open one yourself. The program that created it knows how to read it, and that is usually all that matters.
Key Takeaways
- DAT files are generic data containers created by software programs, and the same extension can hold completely different types of information depending on which program made it.
- Most DAT files live in system or program folders and are used by the software that created them, not by you directly.
- You should not delete a DAT file unless you are certain which program created it and that you no longer need that program's data.
- If you find a suspicious DAT file in an unexpected location, running a malware scan is safer than opening it or deleting it blindly.
Where DAT files come from and what they do
Windows and macOS both use DAT files for system functions. Windows Update stores temporary files with .dat extensions. Your browser may create DAT files to cache data or store cookies. Media players like Windows Media Player use DAT files to hold library information. Antivirus programs create DAT files to store virus definitions — the list of known threats they check against.
Third-party software does the same thing. If you use Skype, it creates DAT files to store chat history and contact information. If you use Blender for 3D modeling, it uses DAT files for project data. The program knows what format it put the data in, so it can read it back correctly. You do not need to know the format — the software handles that automatically.
The reason programs use DAT instead of a more specific extension is usually convenience or secrecy. A developer might not want users poking around in the file, or they might want to change the format later without changing the extension. DAT is a way of saying "this is data, but not your concern."
Common DAT files you might see on Windows
If you open File Explorer and navigate to hidden system folders (by turning on "Show hidden files" in View settings), you will find DAT files in several standard locations. The folder C:\Windows\System32 contains system DAT files that Windows itself uses. The folder C:\Users\[YourUsername]\AppData contains DAT files created by programs you have installed — this is where browser caches, chat histories, and program settings often live.
Some DAT files you might recognize by name include thumbs.db (Windows stores thumbnail previews here), desktop.ini (folder display settings), and various files in the Temp folder (temporary data that programs create while running). None of these need your attention under normal circumstances.
If you see a DAT file with an unfamiliar name in an unexpected location — for example, in your Documents folder or on your Desktop — that is worth investigating, but not by opening it. Instead, right-click it, select Properties, and look at the "Created" date and the program listed under "Opens with." That tells you which software made it and when.
When a DAT file might be a security concern
DAT files themselves are not inherently dangerous, but malware sometimes uses the DAT extension to hide. A malicious program might name itself something.dat to blend in with legitimate system files. The risk is not the extension — it is the source. If a DAT file arrived as an email attachment, came from a download link you did not recognize, or appeared on your computer without explanation, that is a reason to be cautious.
The safest approach is to run a malware scan before touching it. Windows Defender (built into Windows) or a third-party scanner like Malwarebytes can check the file without opening it. If the scan comes back clean, the file is almost certainly safe. If it flags something, the scanner will usually offer to remove it automatically.
Do not open a suspicious DAT file in a text editor or try to delete it manually if you are unsure. Deleting a system DAT file by mistake can break Windows or a program you rely on. Scanning first takes two minutes and tells you exactly what you are dealing with.
How to find out what a specific DAT file does
If you want to know what a particular DAT file is for, start with its location and name. A file called nvapps.dat in your AppData folder belongs to NVIDIA graphics drivers. A file called WSUS.dat in System32 belongs to Windows Update. Searching the exact filename in a search engine usually returns results from forums or documentation that explain what it is.
You can also check the file's properties. Right-click the DAT file, select Properties, and look at the Details tab. The "File version" or "Product name" field sometimes tells you which program owns it. If that is blank, look at the "Date modified" — if it matches when you installed a particular program, that program probably created it.
If you still cannot figure out what a DAT file is, leaving it alone is the right choice. System and program DAT files are meant to stay where they are. Deleting them can cause problems, and you gain nothing by opening them.
Should you delete DAT files to free up space
Deleting DAT files is rarely a good way to free up disk space, and it often causes problems. A system DAT file that you delete might be recreated by Windows or your program the next time it runs, wasting your effort. Worse, deleting a DAT file that a program depends on can cause that program to crash or lose data.
The safe files to delete are temporary DAT files in your Temp folder — C:\Users\[YourUsername]\AppData\Local\Temp — but even then, only delete files that are not currently in use. Windows usually cleans this folder automatically over time, so there is no urgent reason to do it yourself.
If you need to free up space, uninstalling programs you no longer use is much more effective and safer. If a program creates a large DAT file that you want to remove, uninstall the program instead of deleting the file manually. The uninstaller knows which files belong to the program and which ones to leave alone.
Frequently Asked Questions
Can I open a DAT file to see what is inside?
You can try opening it in a text editor like Notepad, but you will usually see gibberish — random characters and symbols — because the data is stored in a format only the original program understands. If you need to see the data, use the program that created the file instead. If you do not have that program, the file is probably not meant for you to read.
Is it safe to delete a DAT file I found on my Desktop?
It depends on where it came from. If a program you installed created it, deleting it might cause that program to lose data or stop working. If it arrived as an email attachment or from an unknown source, run a malware scan first. After the scan comes back clean, you can safely delete it if you do not recognize the program that owns it.
Why do programs use DAT instead of a real file type?
DAT is generic and flexible — a developer can change the internal format without changing the filename. It also signals to users "this is not a file you should edit manually." Some programs use DAT to keep their data format private or to avoid compatibility issues if they update the format later.
What should I do if my antivirus found a DAT file and flagged it?
Follow your antivirus program's recommendation. If it says to remove the file, let it do so — antivirus software is designed to recognize malware and knows whether a flagged file is actually dangerous. If you are unsure, you can quarantine the file instead of deleting it, which isolates it safely while you research what it is.
Do I need to back up my DAT files?
System and program DAT files are recreated automatically by Windows and your software, so backing them up is unnecessary. The only DAT files worth backing up are ones that contain data you created — for example, a DAT file from a program you use for work. When in doubt, back it up; it takes no extra effort if you are already backing up your Documents folder.