File Extension Database

Search our comprehensive file extension database to discover the format of an unknown file and find programs that can open it.

Inside our database, you’ll find:

20,000+ file extensions
8,000+ software tool
10,000+ file converters

Browse files from A to Z by file extension

Drag and drop or upload a file to analyze its format (up to 50 MB).

Add a file extension Contribute information about a new extension.

Tips for Opening Unknown File Formats

What is a file extension?

A file extension is the string of characters that follows the last dot in a filename. It helps your operating system determine which program can open the file. For example, «.txt» is used for plain text files.

How can I look up file extension info?

Use the search box to find the extension you’re curious about. Each result includes a detailed description and a list of software that supports the format.

How do I open an unknown file?

Select your operating system from the list and download one of the suggested programs. If the file extension is associated with a tool, double-clicking it may open the file automatically.

Top Extensions This Week

1 .MDF - Media Disc Image Format
2 .CDA - CD Audio Track
3 .REG - Registry Format
4 .DO - Java Servlet
5 .XHT - XHTML Format
6 .ASCX - ASP.NET User Control Format
7 .10O - Toyota Embroidery Format
8 .DHTML - Dynamic HTML Format
9 .DOC - Microsoft Word Document
10 .RESP - Microsoft Windows Report Log

Popular Software Tools

1 Aiseesoft MXF Converter (14 file associations)
2 PowerDirector (34 file associations)
3 Microsoft Access (68 file associations)
4 Microsoft Windows 3.x (25 file associations)
5 Babel3D (28 file associations)
6 MAME (12 file associations)
7 BBEdit (9 file associations)
8 PhraseExpress (10 file associations)
9 dBASE (61 file associations)
10 Avid Media Composer (9 file associations)

Recommended File Converters

1 WMV to MPEG (13 program)
2 TIFF to GIF (18 program)
3 MKV to MP4 (21 program)
4 PLY to OBJ (16 program)
5 DAE to 3DS (16 program)
6 MOV to DIVX (11 program)
7 ALAC to MP3 (9 program)
8 MP4 to OGG (10 program)
9 3GP to VOB (20 program)
10 ARW to CR2 (9 program)