CAT File

What are CAT files and how to open them

Are you having problems opening a CAT 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 CAT files.

What is a CAT file?

CAT files have multiple uses, and Microsoft Security Catalog is one of them. Read more about the other uses further down the page.

Microsoft Security Catalog File

A security catalog file is a digital signature for a collection of files. A catalog file contains a collection of cryptographic hashes - one for each file in the collection.

Plug and Play device installation recognizes the signed catalog file of a device driver package as its digital signature, where each "thumbprint" in the catalog file corresponds to a file that is installed by the driver package.

How to open CAT files

Important: Different programs may use files with the CAT file extension for different purposes, so unless you are sure which format your CAT file is, you may need to try a few different programs.

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

Last updated: August 31, 2026

All known file formats using extension .CAT

While Microsoft Security Catalog File is a popular type of CAT-file, we know of 10 different uses of the .CAT file extension. Different software may use files with the same extension for different types of data.

Casio Calculator Tape Format

Casio Calculator Tape Format stores text-based records exported from Casio FA-122 / FA-123 / FA-124 series calculator link software. It is used to save programs, backups, pictures, lists, matrices and other calculator data in a human-readable file so that the content can be viewed, edited or transferred back into a calculator. These files are good for keeping a catalog of calculator items on a computer or sending specific items back to the device.

Files of this format are created by Casio's FA-124 (or older FA-122 / FA-123) PC link software when the user uses Save or Export commands with type "CASIO file (*.cat)". They may contain multiple records in one file; each record describes one item (program, picture, or backup) using a header block, followed by its data block. The format supports transferring items from computer to calculator and vice versa.

Header fields in each record include items such as Format, Communication SW, Data Type, Capacity, File Name or Data Name, Group Name, Model, one or more Option fields. The data blocks encode the actual content: programs as tokenised text, backups as hexadecimal memory dumps, pictures as sheet- and color-organized hex lines.

Files begin with a signature line including "%Header Record" and "Format:" headers, and contain tags like COMMUNICATION SW, DATA TYPE, OPTION, NAME, and the keyword "%DATA RECORD" to mark the start of data.

Elcomsoft Advanced Disc Catalog File

Elcomsoft Advanced Disc Catalog File is the binary catalog file used by the Advanced Disk Catalog (ADC) program developed by ElcomSoft. It holds a snapshot of file and media contents from various volumes - such as hard disks, network shares, floppy disks, CD-ROMs, ZIP, JAZ and other removable media. Its purpose is to index filenames, folder structures, volume labels, and optionally descriptions or comments added by the user, so that a user can view and search through the catalog without needing the media physically connected.

ADC creates these catalog files when scanning or updating one or more volumes. Users can assign categories to files or volumes, add custom comments, and import descriptions from external files like file_id.diz, descript.ion, files.bbs, HTML, PDF or Microsoft Office files. The software allows browsing inside archive types (ZIP, RAR, ARJ, CAB, etc.) and treats archives like folders when extracting metadata, but contents of files are not stored - the catalog stores metadata only. Reports may be generated or exported in external formats (e.g. CSV, XML, DBF).

ADC does not rely on external database engines; it uses its own lightweight format designed for compactness and speed. Its catalog files are proprietary and typically only fully usable by ADC itself. One internal identifier is the ASCII signature starting with "ADC.Catalog" embedded at offset 0x0B000000.

Frostbite Catalog File

Frostbite Catalog File format stores a catalog of game asset entries used by the Frostbite game engine. It is created by the engine's content pipeline to index all assets packed into one or more CAS archive files so that each asset's location, size, and archive number can be resolved quickly.

The file is produced alongside CAS archive files. The engine writes it so that the game's asset loader can read the catalog when resolving requests by SHA1 hash to find which CAS file contains the data, where inside it (offset and length), and which catalog entry matches. The catalog is not used for raw asset data, only for locating them.

The file begins with the ASCII signature "NyanNyanNyanNyan" at byte 0. Immediately following the signature the file contains repeated entries, each entry holding a SHA1 hash (20 bytes), a 32-bit offset, a 32-bit size, and a 32-bit CAS file index identifying which CAS archive the asset resides in.

HotHelp Catalog File

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

ImageDesk Catalog

ImageDesk Catalog files are used by ImageDesk, an Amiga software tool written by Ralf Haslbeck. These catalog files store a directory's contents of image files plus small thumbnail previews. The program builds a catalog so that users can browse image collections more quickly without opening each full-size image file.

The .CAT file is created by ImageDesk when pointing it at a folder of images; it stores thumbnail representations and essential metadata (such as filenames, image formats, and image attributes) about each image in the source folder. Users load the catalog in ImageDesk to view thumbnails and later open any image listed.

These catalog files begin with a four-byte ASCII signature "IDCA" at offset zero, which ImageDesk uses to identify the file as its catalog format.

Maxon Cinema 4D Catalog

We know that one CAT format is Maxon Cinema 4D Catalog. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Starcat Disks Catalog File

We know that one CAT format is Starcat Disks Catalog File. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Upcat Catalog

Upcat Catalog files serve as disk catalogs created by the Upcat program for the Amiga, written by Frans Zuydwijk. They hold an index of files found on one or more disks, including metadata such as file names, sizes, dates, categories, and user-supplied comments. Upcat's main purpose is to scan disks and record their contents in these catalog files so users can browse, search, display, print, or selectively view entries without having the disks physically mounted. Upcat supports grouping records under any of 32 user-definable categories and offers features like ARexx scripting to automate operations. It reads disk directories, stores catalog information in memory, and allows saving catalogs to disk for later loading.

The files are generated by Upcat (disk catalog program version 1.x for AmigaDOS 2.04 or higher) and are meant to be opened by the same program. Catalogs are used to review contents in several views, make selections, print reports, add comments to individual records, and to reuse across sessions. Once a catalog file is produced it basically functions as a searchable database of what was on scanned disks.

On the technical side, Upcat Catalog files begin with ASCII text at the very start: the first bytes are "UpcatCatalog.Categories\nCategories\n" (in hexadecimal: 55 70 63 61 74 43 61 74 61 6C 6F 67 0A 43 61 74 65 67 6F 72 69 65 73 0A). Somewhere in the file there is also the keyword "RECORDS", which denotes where the actual catalog entries start. These signatures help distinguish these files from other .CAT files by other unrelated programs.

WinCat Disk Catalog File

We know that one CAT format is WinCat Disk Catalog File. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Various apps that use files with this extension

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

Help us help others

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