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Plugin framework for HxD's data inspector

This plugin framework allows to create extensions for HxD's data inspector, as plugin DLLs, which can be written in Delphi, C, C++, or PureBasic (external).

Any other language that can create DLLs and export C like functions should work equally well (but you would need to translate the C headers).

Currently, you can write data type converters, such that byte sequences can be translated to strings and strings to byte sequences.


  • Variable width encodings (such as UTF-8 code points, or x86 assembly) as well as fixed width encodings (such as 32-bit integers, or single precision floats) are supported.

  • You can override the handling of byte reordering (little endian vs. big endian) to customize it for your type specific requirements, such as mixed endianness.

  • Finally, navigating to the next/previous or first/last "array" element is supported by default, with the additional ability to customize to type specific needs (especially necessary for variable width encodings).

Coding conventions

Identifiers are named in a Delphi-typical manner, also in the C and C++ versions, to make it easier to keep the interfaces in all languages in synch (the original being in Delphi, just like HxD itself). That means types begin with a T and pointer types begin with a P. Fields (member variables in C++) begin with an F.

This concerns contributions to the plugin framework itself. You are free to use your own coding conventions for your plugins, obviously.

Quick start

There are example projects that make it simple to quickly get you started writing your data type converter. See DataInspectorPluginExample.dproj for Delphi, and DataInspectorPluginExample.sln for C/C++ (Visual Studio).

Make sure to place the created DLL in the Plugins folder, which is at the same level as HxD.exe. Then simply start HxD, and your newly defined types will appear in the data inspector.

If they are missing or have the wrong name, right-click on the data inspector, select "Options..." and click "Reset". A 32 bit and 64 bit version of the plugin is needed to support HxD fully; put the right one in the Plugins folder for the bitness of HxD you have installed.

Folder structure:


(Both files, HxD.exe and the plugin DLL, must be either 32 or 64 bit.)

Use HxD 2.5 or higher to test / develop your plugins (using the portable is simpler, since creating a Plugins directory does not require admin rights):

Non-OO interface: plain Delphi / plain C

There is a basic procedural API, that works in plain Delphi and C, and can be found in and DataInspectorPluginInterface.h, respectively. declares all the functions that need to be exported. Additional types are declared in DataInspectorShared.pas/.h.

Memory management is simple: the plugin DLL manages its own memory and HxD does so with its own, as well. Therefore, there is no need to use a shared/central memory manager. HxD guarantees that every string or byte array, that is returned by the plugin, will be copied immediately, after the function call. So it is sufficient to return references to strings or byte arrays, and free them on the next call of the same function.

For example, BytesToStr() returns a string. Store the result in a global variable or a member variable, and return a reference to it. Keep the variable unchanged until BytesToStr() is called again.

See the OO interface for an implementation of this strategy, if you need more details, or refer to the plain C example. If possible, use the simple OO solution directly (see below).

OO interface (more comfortable): Delphi / C++

A more comfortable OO solution is provided in DataInspectorPluginServer.pas and DataInspectorPluginServer.h/.cpp.

The simple base class TExternalDataTypeConverter presents a nicely abstracted interface, from which you can derive a class for your type converter, and only need to override a couple methods to implement it.

Calling RegisterDataTypeConverter() in DllMain() is the only remaining task.

See the example projects for details!

The DataInspectorPluginServer unit/module handles everything else for you: from providing implementations for the necessary functions, that define the raw plugin interface, to handling memory. It also automatically creates class instances of the right TExternalDataTypeConverter descendants, and translates between the plain data types / function pointers and class instances / methods, seamlessly.

Implementation guidelines

For details on what the data type conversion functions have to do exactly, and what the interface contracts are, check out the implementation guidelines.


Debugging works like debugging any DLL project.

  • Delphi

    • Specify HxD.exe with its full path as the host application in the IDE (Start|Parameter...). Also set the working directory to the dir of HxD.exe.
  • VC++

    • Specify HxD.exe with its full path as command (Project options|Debugging|Command). Also set the working directory to the dir of HxD.exe.

Note: Make sure that the generated DLL is really created in the Plugins folder of HxD. You have to adapt the project options accordingly!

Publishing your plugin

If you wrote a plugin that you would like to share (link from here or my website), please contact me by mail, so we can discuss the details.

Even if you don't intend to publish it, letting me know what you did, would still be interesting to know, as that's part of the motivation to make HxD.

Open source plugins


Copyright (C) 2019-2021 Maël Hörz

The plugin framework is licensed under the MPL. But you are welcome to contact me if another open source license would be more suitable.


HxD hex and disk editor is available at:

See the website for ways to contact me, Maël Hörz, by mail.

For bugs and feature requests related to plugins, please use the issue tracker on GitHub.

For other topics related to HxD, please use the forum: