What Is a CAP File?

How to open, edit, and convert CAP files

A file with the CAP file extension is most likely a Packet Capture file created by packet sniffing programs. This kind of file holds raw data collected by the sniffing program so that it can be analyzed at a later time or with a different program.

Some CAP files might instead be Construct Game Development files. These are project files for DirectX games created with the Scirra 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.

CAP is also a subtitle/caption file format that stores text meant to be played along with a video. It's used by some broadcasting companies and might be called a Videotron Lambda file.

How to Open a CAP File

Illustration of a person opening a CAP file
Lifewire / Adrian Mangel

Packet Capture files can be opened with the free Wireshark program. Although we don't have download links for them, some other applications that support opening this kind of CAP file include NetScout's Sniffer Analysis and Klos PacketView Pro.

Scirra Construct is probably your best bet if it's a Construct Game Development file.

ASUS BIOS Update files are used to update the BIOS only on ASUS motherboards.

CAP subtitle files can be opened with EZTitles and probably other subtitling software.

You might be able to use Notepad or a different free text editor to open your CAP 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.

Considering the various types of CAP files there are, and that several different programs might be involved depending on the actual format being used in the file, you may find that the program Windows tries to use to open CAP-type files isn't the one you'd like. See our How to Change the Default Program for a Specific File Extension piece for help fixing that problem.

How to Convert a CAP File

You can convert a Packet Capture file to HCCAP with hashcat, or to CSV, TXT, PSML (XML Packet Summary), PDML (XML Packet Detail), or C (C Arrays Packet Bytes) with Wireshark.

If you're using Wireshark, 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 Game Development file or a BIOS Update file to another format.

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

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 aren't related.

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.
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