What Is a CAP File?

This article details the several formats that use the CAP file extension, and how to open each type.

What Is a CAP File?

Some packet sniffing programs store packet capture files with the CAP file extension. It holds raw data collected by the program so that it can be analyzed at a later time or with a different program.

Other CAP files could be project files for DirectX games created with the Construct game editing software. They can contain sounds, graphics, models, and other things used by the game.

This extension is also related to ASUS motherboards as the file used when updating BIOS. It's also related to a subtitle/caption file format that stores text meant to be played along with a video; this kind of file is used by some broadcasting companies and might be called a Videotron Lambda file.

How to Open a CAP File

There are several ways to use the file, depending on the format it's in:

• Use Wireshark to open packet capture files. Some other applications that work include NetScout's Sniffer Analysis and Klos PacketView Pro.
• Construct is probably your best bet if it's a game-related file.
• ASUS BIOS update files are used to update the BIOS on ASUS motherboards.
• Experiments created by Capstone use this extension.
• Some versions of Capella can be used to open CAP files that are musical scores. The free Capella Reader might support the format, too.
• Videotron Lambda CAP files are compatible with EZTitles.
• Although rare, some CAP files are RAW images associated with Capture One software.

You might be able to use Notepad or a different free text editor to open the file. Many files are text-only files, meaning no matter the file extension, a text editor may be able to properly display the file's contents. This may or may not be the case with your specific CAP file, but it's worth a try if the above suggestions haven't been helpful.

How to Convert a CAP File

You can convert a packet capture file to HCCAPX with hashcat.

Use Wireshark to save it to CSV, TXT, PSML, PDML, JSON, or C. You have to first open the file through the File > Open menu, and then go to File > Export Packet Dissections to choose an output format.

There's no reason to convert a Construct file or a BIOS file to another format.

Subtitles ending in this file extension can be converted to TXT, PAC, STL, SCR, and other file formats, using the subtitling program mentioned above.

RAW images that end in .CAP can be converted to other image formats with Filestar.

Still Can't Open It?

If the file openers and converters listed above aren't helpful, double-check the file extension. There's a good chance you're misreading it. Several files use a similar extension to this one, even though the formats are unrelated.

CPA is one example. Although all the same letters are used, that extension is reserved for CADSTAR CAD files. CPAA is similar in spelling, but is what Adobe Captivate appends to the end of shared action files. CAPT, CAT, and CAPX could also easily be confused for a CAP file.

Frequently Asked Questions

• How do you install a CAP file? To install a CAP file for a BIOS update, first copy the CAP file to a formatted USB flash drive. You can then use the ASUS EZ Flash utility (built into the ASUS BIOS firmware) to load the BIOS update.
• How do I open a CAP file in Ubuntu? Open your terminal and type locate *.cap to find all CAP files, and then download a file opener such as Wireshark to open the file.