CAP File

What are CAP files and how to open them

Are you having problems opening a CAP file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CAP files.

What is a CAP file?

CAP files have multiple uses, and Scirra Construct Game Data is one of them. Read more about the other uses further down the page.

Scirra Construct Game Data File

The .cap file extension is most commonly used for game development files. These files are created by the Scirra Construct programming application to create DirectX 9-based computer games.

The CAP files contain the background images, objects, event handlers, physics models, and other code used to create the game.

How to open CAP files

We have identified one CAP opener that is compatible with this specific type of CAP file.

Programs that open Scirra Construct Game Data files

Last updated: August 25, 2026

All known file formats using extension .CAP

While Scirra Construct Game Data File is a popular type of CAP-file, we know of 9 different uses of the .CAP file extension. Different software may use files with the same extension for different types of data.

Capella Music Notation

Capella Music Notation files are a proprietary binary format used by Capella, a scorewriter program developed by Capella-software AG in Germany. These files store fully notated musical scores, including staves, notes, rests, lyrics, articulations, dynamics, clefs, and key/time signatures, in a compact non-textual representation. They are the program's native format for editing, saving, and sharing music scores in binary form.

This format is produced by Capella versions 2 through 6 (and versions 7-when using its legacy binary mode). Starting with Capella version 7, the program also supports an XML-based format called CapXML (extension .capx) alongside the binary format. When saving in binary, Capella writes all musical content and formatting directly in binary rather than via XML.

In workflow terms, Capella reads these binary files for editing or playback, and writes them when a user explicitly saves in binary mode. When interoperability is needed (for example sharing with other programs or for archiving), users may instead use the XML-based CapXML format. Capella also supports import/export with standard formats like MusicXML.

Files in this binary format are identified by a specific byte signature at the start of the file, namely the sequence 0x89 0xE2 0xB3 0x74 at offset zero. Internally the format is versioned (e.g. CAP2, CAP3) as Capella's major versions evolved; some content such as lyrics or expressive markings may have been lost or changed when converting between older and newer binary versions.

While we have not verified the apps ourselves yet, our users have suggested ten different CAP openers which you will find listed below.

Capella Music Sheet File

Capella Music Sheet File (extension .CAP) is a proprietary binary file format used by the Capella music notation program (by capella-software AG) for saving musical scores prior to Capella 7. These files store complete musical scores including notes, rests, chords, staffs, time-signatures, lyrics, and layout information for playback, editing, and printing.

Files with this extension are created by older versions of Capella (for example Capella versions through 2000-2006) using its Binary CAP format, which preceded the XML-based CapXML format (extension .CAPX) introduced in Capella 7. Users continue to open, edit, print or play .CAP files using Capella or Capella Reader, though newer versions favor the .CAPX format.

Internally the .CAP binary files begin with the ASCII signature "cap3‐v:a" at offset zero (also containing the string "CAP3-V:A"), which identifies them as the CAP3 version of Capella's binary score format.

CAP opener for Windows

We have identified one CAP opener that is compatible with this specific type of CAP file.

IBM Storyboard Screen Capture File

We know that one CAP format is IBM Storyboard Screen Capture File. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Java Card Converted Applet

A Converted Applet file is a type of file that holds a smart card application or library written in Java and transformed into a compact, optimized form so it can be loaded onto devices that run Java Card. It combines all the classes in one or more Java packages into a format suitable for constrained environments, such as smart cards. The conversion takes place off the card (on a development machine), using a tool known as the Java Card Converter. Following conversion and optional verification, the file is installed on the smart card via an installer component that understands the Java Card CAP format.

The format represents either a standalone application (one or more applet packages), or a library (or both), possibly with shared packages that other CAP files may import. Within a CAP file are several components: a header with package metadata (including version and package identifier), a directory of component sizes, definitions for imports, constant pool, classes, methods, static fields, reference locations, and optional pieces like applet information, exportable elements, debugging details, or static resources. The format exists in two main versions: "Compact," for CAP files with a single package and smaller sizes; and "Extended," allowing multiple packages in one CAP and method sections larger than 64 KB.

Internally a CAP file is a JAR container: the components are stored as files inside directories arranged by package name, under a subdirectory named javacard. It begins with a header component including a magic number (0xDECAFFED), version info, package flags and identifier. Components are tagged, sized, and contain info like class or method definitions. Developers tools generate these during build; smart cards read and interpret them for execution.

Byte-level identifiers include the magic header value in the header component (0xDECAFFED), as well as internal component filenames and field tags like Header, Directory, Applet, Import, ConstantPool, Class, Method, StaticField, RefLocation, Descriptor, Export and strings such as "JAVACARD." The file often begins with byte sequence "PK" since it uses the ZIP/JAR container format.

Microsoft NetMon Traffic Capture File

Microsoft NetMon Traffic Capture files with the extension .CAP store raw network traffic captured by Microsoft Network Monitor. These files are produced when a user captures packets on one or more network adapters using Network Monitor (for example version 3.4) and then saves the capture session. Their main purpose is to record all frames seen on the selected adapters, including protocol details, timing, and any user or comment metadata, for later examination and troubleshooting. Network Monitor is a protocol analyzer used to collect, view, and analyze network traffic on Windows.

Inside a .CAP file, the data is organized in several segments: a global header that describes version, network medium, and capture start-time; an index (frame table) that locates each frame inside the file; followed by the frame data themselves, plus optional segments for user data, comments, statistics, and network information. After capturing, one typically loads the .CAP file into Network Monitor or another compatible tool to filter, analyze protocol exchanges, compute statistics, or investigate specific packets.

Technically, files start with a four-byte signature "GMBU" which identifies the Network Monitor version 2.x format (version major 2, minor in binary-coded decimal). The header is padded to 128 bytes and includes offsets and lengths for various DATA structures such as FrameTable, CommentData, NetworkInfo, and Statistics.

Programs that open these CAP files

We have identified one CAP opener that is compatible with this specific type of CAP file.

Snoop Capture File

Snoop capture file stores a record of network packets captured by the snoop tool from the Solaris operating system. It is used when "snoop" is run with the option to save its packet output to disk, so that the network traffic can be examined later. Typical uses are network debugging, traffic analysis, performance tuning, or security auditing. The packets are recorded in binary, preserving full packet headers and payload data as they passed over the wire.

The creator of a snoop capture file is the snoop program supplied with Solaris (by Sun Microsystems). Once the file is written, snoop itself can read and display its contents using its "-i" option. Third-party tools such as Wireshark and TShark also support this capture format. The capture includes timestamps, datalink information, and other metadata for each packet, so that later inspection shows when each packet was received, how large it was, and its link-layer context.

The file begins with an 8-byte ASCII signature "snoop" followed by three null bytes at offset zero. This is followed by a 32-bit version number (currently version 2 in modern Solaris releases), a 32-bit datalink type field, and then a sequence of packet records. Each record consists of metadata (original packet length, captured length, timestamp in seconds and microseconds, and other descriptive fields) followed by the packet data and optional padding to align records. All integers are stored in big-endian order.

Ventura Publisher Caption

Ventura Publisher Caption files hold text used for captions, labels and box text that accompany graphics or empty frames in Ventura Publisher chapters. They are automatically generated alongside a chapter file and include all "caption frames," "box text," and blank-frame text entered into a chapter.

Ventura Publisher writes these files when a chapter is saved: one CAP file per chapter, named identically to the chapter but with the CAP extension. Caption file contents insert into layout via frames or boxes tagged as captions or empty frames; users may edit CAP files in external text editors for batch changes to caption text or repeated phrases.

Internally, Ventura treats captions as frame attributes tied to "Anchors & Captions" dialog entries. When creating a caption frame, the format makes two paragraph elements: the first uses a tag like Z_LABEL FIG, Z_LABEL CAP, or Z_LABEL TBL to provide automatic numbering; the second uses Z_CAPTION for the user-entered caption text. In the CAP file, these strings appear among others. The file signature begins with byte 0x40 at offset 0, and includes the ASCII string Z_CAPTION as a marker of caption-text entries.

XCP Network Capture File

We know that one CAP format is XCP Network Capture File. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Programs that open these CAP files

We have identified one CAP opener that is compatible with this specific type of CAP file.

Various apps that use files with this extension

These apps are known to open certain types of CAP files. Remember, different programs may use CAP files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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