DCT File

What are DCT files and how to open them

Are you having problems opening a DCT 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 DCT files.

What is a DCT file?

DCT files have multiple uses, and DACT Compressed Data is one of them. Read more about the other uses further down the page.

DACT Compressed Data

DACT Compressed Data is the output of the Dynamic Adaptive Compression Tool, a lossless compressor that divides any input file into blocks and compresses each block using a variety of algorithms. It then selects the best-performing algorithm per block to minimize overall size.

These files are created exclusively by the DACT program developed by Roy Keene. During compression the user may specify block size; metadata such as original file size, block size, version of DACT used, file name, and checksums are stored in the file header. In order to decompress a DACT Compressed Data file the DACT program must be used, reversing the per-block algorithm selections.

A DACT Compressed Data file begins with a fixed four-byte magic number equal to 0x444354C3 at offset zero. The header also includes the DACT version, the block size in use, and the uncompressed size of the original file.

How to open DCT files

Important: Different programs may use files with the DCT file extension for different purposes, so unless you are sure which format your DCT 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 DCT openers which you will find listed below.

Last updated: October 22, 2026

All known file formats using extension .DCT

While DACT Compressed Data is a popular type of DCT-file, we know of 10 different uses of the .DCT file extension. Different software may use files with the same extension for different types of data.

DCT Bitmap

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

Electronic Arts DCT Video File

Electronic Arts DCT Video File is a game cut-scene video format. It is created by Electronic Arts and used in EA games from the late 1990s, most notably in Need for Speed II and FIFA '98. The format stores compressed video (and sometimes audio) sequences such as intros, track demonstrations or car unlock scenes for efficient playback inside the game engine on PC or PlayStation.

EA builds these files by encoding frame data using the PlayStation's Motion Decoder (MDEC) codec, preceded by a small header that supplies basic layout information including image width and height. Games then decompress the MDEC stream at runtime for display at fixed framerates (samples of known files play at 15 frames per second).

Technical detail: the header begins with a FourCC tag "mTCD", followed by a 32-bit little-endian value (purpose unknown), then two 16-bit little-endian words giving the image width (pixels) and height. After that, the rest of the file is a raw MDEC bitstream.

DCT opener for Windows

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

IBM PS/55 MKKC Dictionary

IBM PS/55 MKKC Dictionary files store the vocabulary data used by the IBM PS/55's Japanese input method, specifically for Kana-to‐Kanji conversion. These files are built by IBM to support converting phonetic Kana input into the corresponding Kanji candidates in the PS/55 environment, under Microsoft's Kana-Kanji Conversion (MKKC) system.

The format is written out by IBM's tooling for the PS/55 and MKKC versions (v3.x). It is read by the input method system when the user enters Kana characters and presses the conversion key ("henkan") to choose a Kanji form. The dictionary contains entries mapping Kana readings to Kanji representations, along with internal ordering, indexing, and possibly frequency or selection metadata for candidate presentation.

Internal identification of this format is achieved via multiple signature strings near the start of the file. A visible ASCII header begins with "IBMPS/55MKKCDICTIONARYV3" at offset zero. Around byte 42 is the copyright notice "(c)CopyrightIBMCorp.19". Other phrases contained in the file are "LICENCED MATERIALS-PROPERTY OF IBM" and "(C) COPYRIGHT IBM CORP. 19", plus "IBM PS". These markers distinguish this dictionary file from other, unrelated formats that also use the same extension.

MicroPro SpellStar Dictionary

We know that one DCT format is MicroPro SpellStar Dictionary. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

NCH Dictation Audio File

NCH Dictation Audio File (.DCT) is a proprietary audio format used by NCH Software in its dictation tools for storing spoken recordings together with metadata. It is created by programs like DialDictate, Express Dictate, Express Scribe, and other NCH dictation or transcription systems. A file of this type typically includes the voice recording, information about the sender or speaker, priority, reference numbers, and can be optionally encrypted for confidentiality.

Files in this format often use compression (with selectable codecs), and may support multichannel recording - storing more than one audio channel in a single file. The format also embeds file-management information such as checksums and tracking fields so that the recordings can be managed automatically, for example when sent to typists or transcription services. If the user wants greater compatibility, recordings can instead be saved in WAV format; however, WAV does not include metadata like sender or allow encryption.

Technically, a .DCT file from NCH begins with a signature at offset 0 of bytes 0x0000, followed by a series of other identifying byte patterns (e.g. 0x01000000000000000000 at offset 4, 0x000000 at offset 15, 0x09375D at offset 19) and contains ASCII strings such as RIFF, DATA, WAVEFMT, and others. These help software detect and validate the file type.

Programs that open these DCT files

We have identified 2 DCT openers that are compatible with this specific type of DCT file.

RightWriter Dictionary File

Files containing the .dct file extension are most commonly associated with dictionary files used by various spell-checking and grammar correcting applications, including RightWriter.

Programs that open these DCT files

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

SDict Dictionary

We know that one DCT format is SDict Dictionary. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Team6 Game Data

We know that one DCT format is Team6 Game Data. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

WPSpell Dictionary

WPSpell Dictionary files store word lists used by the WPSpell spell-checking engine, a component of WPTools produced by WPCubed GmbH. They enable WPSpell to recognize valid words and flag misspellings when integrated into text editing applications built with WPTools.

These dictionary files are created by WPCubed's WPSpell component, typically when building or installing additional language support for spell checking. WPTools loads them to compare text input against the word list; applications using WPTools with WPSpell let users select which dictionary file to use, and the file remains purely a list of approved words, not formatting or markup.

The format begins with a specific ASCII header signature: at offset zero there are 48 bytes spelling ".WPSpell Dictionary - www.wpcubed.com"; that signature uniquely identifies this type in files with that extension.

Various apps that use files with this extension

These apps are known to open certain types of DCT files. Remember, different programs may use DCT 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

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about DCT file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.