Opening CAP files

Have a problem opening a .CAP file? We collect information about file formats and can explain what CAP files are. Additionally we recommend software suitable for opening or converting such files.

What is the .CAP file type?

Stemming from 'capture,' the .cap filename extension primarily represents the Wireshark Packet Capture (.cap) file type and format. Wireshark is a free, open source network packet analyzer with a host of advanced traffic capture and filtering features for both Unix-like OS'es and Microsoft Windows.

The .cap file contains a low-level dump of packets captured by Wireshark from a live network interface and saved in Wireshark's native format for later examination. Such files can be opened in Wireshark and exported to a range of other network-capture formats.

Apart from Wireshark, the .cap filename extension is commonly used by several other network analyzers (e.g., Microsoft Network Monitor, tcpdump, Network Associates Sniffer, etc.) to denote their packet capture files, each in its own format. Wireshark fully supports most of the alternative packet capture formats.

The .cap extension also represents the newer BIOS firmware image format (CAP) developed by ASUSTeK for a range of their mainboards (MB) with Intel chipsets, like P9X79 PRO. The .cap file is a BIOS firmware image that describes 'capabilities' of a given MB, according to the Unified Extensible Firmware Interface (UEFI) BIOS standard.

Before any .cap file can be used to update BIOS, the BIOS structures themselves must be converted to the CAP format, using the BIOS Converter tool provided by ASUSTeK for several MB models. For the CAP upgrade to work, the BIOS Converter file must be renamed in a special way. Switching to the CAP BIOS format allows for better compatibility with Microsoft OS'es, like Windows 8.

Additionally, the .cap extension denotes the generic Closed Captions File (.cap) file type. Typically used in broadcast TV and video, Closed Captions (CC) are standardized (CEA-608) hidden subtitles that can be triggered on by the viewer. The .cap file is a binary file in one of the several CC formats (Cheetah, NCI, or Captionmaker). Produced with several CC authoring programs or converted from other subtitle formats, such .cap files can be used to fill CC tracks in movie authoring/mastering.

Software to open or convert CAP files

You can open CAP files with the following programs:
Wireshark by The Wireshark developer community,
Wireshark by The Wireshark developer community,
Microsoft Network Monitor
Microsoft Network Monitor by Microsoft Corporation
capella by capella software AG
PASCO Capstone
PASCO Capstone by PASCO scientific

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