CAP File Extension

What is CAP file?

The CAP file is a packet capture file, generated by packet sniffing program. These files are also called a trace file or bone file and are used by numerous packet sniffer programs. These CAP files consist of raw facts and figures that are collected by the sniffing programs so that the data could be evaluated later on or even with a different program. CAP extension files that are Packet Capture files can be accessed using the free Wireshark or Microsoft Network Monitor program. There are some other applications as well that can help with accessing the .CAP packet capture files including NetScout`s Sniffer Analysis and Klos PacketView Pro, and others. 

Programs which support CAP file extension

Below you will find an index of software programs that can be used to open CAP files divided into 3 categories according to system platform supported. CAP files can be encountered on all system platforms, including mobile, yet there is no guarantee each will properly support such files.

Updated: 12/04/2023

How to open file with CAP extension?

There can be multiple causes why you have problems with opening CAP files on given system. What is important, all common issues related to files with CAP extension can be resolved by the users themselves. The process is quick and doesn’t involve an IT expert. The list below will guide you through the process of addressing the encountered problem.

Step 1. Download and install Netscout Sniffer

The most common reason for such problems is the lack of proper applications that supports CAP files installed on the system. This one is an easy one. Select Netscout Sniffer or one of the recommended programs (for example, Wireshark, BoneLight, PacketView Pro) and download it from appropriate source and install on your system. On the top of the page a list that contains all programs grouped based on operating systems supported can be found. The safest method of downloading Netscout Sniffer installed is by going to developer’s website () and downloading the software using provided links.

Step 2. Check the version of Netscout Sniffer and update if needed

If you already have Netscout Sniffer installed on your systems and CAP files are still not opened properly, check if you have the latest version of the software. Sometimes software developers introduce new formats in place of that already supports along with newer versions of their applications. This can be one of the causes why CAP files are not compatible with Netscout Sniffer. All of the file formats that were handled just fine by the previous versions of given program should be also possible to open using Netscout Sniffer.

Step 3. Assign Netscout Sniffer to CAP files

After installing Netscout Sniffer (the most recent version) make sure that it is set as the default application to open CAP files. The process of associating file formats with default application may differ in details depending on platform, but the basic procedure is very similar.

The procedure to change the default program in Windows

• Clicking the CAP with right mouse button will bring a menu from which you should select the Open with option
• Select Choose another app → More apps
• To finalize the process, select Look for another app on this PC entry and using the file explorer select the Netscout Sniffer installation folder. Confirm by checking Always use this app to open CAP files box and clicking OK button.

The procedure to change the default program in Mac OS

• By clicking right mouse button on the selected CAP file open the file menu and choose Information
• Proceed to the Open with section. If its closed, click the title to access available options
• Select Netscout Sniffer and click Change for all...
• If you followed the previous steps a message should appear: This change will be applied to all files with CAP extension. Next, click the Continue button to finalize the process.

Step 4. Check the CAP for errors

If you followed the instructions form the previous steps yet the issue is still not solved, you should verify the CAP file in question. Being unable to access the file can be related to various issues.

1. Check the CAP file for viruses or malware

Should it happed that the CAP is infected with a virus, this may be that cause that prevents you from accessing it. Scan the CAP file as well as your computer for malware or viruses. If the CAP file is indeed infected follow the instructions below.

2. Ensure the file with CAP extension is complete and error-free

If the CAP file was sent to you by someone else, ask this person to resend the file to you. The file might have been copied erroneously and the data lost integrity, which precludes from accessing the file. It could happen the the download process of file with CAP extension was interrupted and the file data is defective. Download the file again from the same source.

3. Check if the user that you are logged as has administrative privileges.

There is a possibility that the file in question can only be accessed by users with sufficient system privileges. Switch to an account that has required privileges and try opening the Packet Capture Format file again.

4. Verify that your device fulfills the requirements to be able to open Netscout Sniffer

The operating systems may note enough free resources to run the application that support CAP files. Close all running programs and try opening the CAP file.

5. Check if you have the latest updates to the operating system and drivers

Latest versions of programs and drivers may help you solve problems with Packet Capture Format files and ensure security of your device and operating system. Outdated drivers or software may have caused the inability to use a peripheral device needed to handle CAP files.

Do you want to help?

If you have additional information about the CAP file, we will be grateful if you share it with our users. To do this, use the form here and send us your information on CAP file.