It was decided to put the code necessary to run publications in a single external program file called the runtime viewer or runtime module. This module is a program that allows publications to be run: it works like the Visual Basic DLL runtimes, the Macromedia Flash player, Windows Installer runtime, etc...
When you run a publication, the latter will simply launch the runtime module which will open the publication and display it.
Since this runtime module is not available on all user computers, it should be normally merged within the publication .exe file, so you get a single stand-alone .exe file to distribute to your end users (without the need to give them any additional file). However this runtime takes about 1,0 Mb (still enough small compared to other web browsers' distribution files) so you can also wish not to merge it. To save a lot of bytes, especially if you create and distribute multiple publications, the runtime module may not be merged into the publication .exe file. In this case, you will get "light" .exe files and you only need to distribute/install the shared runtime module only once.
If the runtime viewer is NOT merged:
If you decide not to merge the runtime module, you must provide your end users with it. But do not worry, there are a lot of solutions. The runtime modules are available in small Setup distribution files, ready to be distributed along with your publication files; or they can be downloaded for free from the HTML Executable website (see below for URLs). You can even upload them to your websites if you wish.
The runtime module needs to be installed on the user computer like any program (it also comes with a uninstall program so end users can remove it if they do not need it anymore). Note that it does not contain any spyware, system and shell add-ons; it won't hurt or cause damages to the user system. This is just a regular single DLL companion file called by publications.
If the runtime module is not found on the user computer when a publication is run, then the publication will display a warning message along with instructions about how to obtain the runtime module for free. You can of course edit these instructions by clicking on "Edit Instructions Text".
If the runtime viewer is merged:
When it is run, the publication tries to locate its runtime viewer on the user system. If it is not found, the publication will first unpack the runtime module from its data to a temporary location and call it. The runtime module is automatically removed when the publication closes, so no trace is left on the user computer.
More information about the HTML Viewer Runtime module
More information about the IE Runtime module
Merge modules for Windows Installer
Merge modules (MSM) are a feature of Windows Installer that provides a standard method for delivering components, insuring that the correct version of a component is installed. A merge module contains a component, such as a .dll, along with any related files, resources, registry entries, and setup logic. To install the information delivered by a merge module with an application, the module must first be merged into the application's .msi file.
All runtime modules of HTML Executable are also available as merge modules if you wish to author a Windows Installer package for your application/publication.