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Difference Between an MSI and EXE File

Difference Between an MSI and EXE File

The extension for a file in Windows that can be used to install an application program could be either .MSI or .EXE. Although the application of both kinds of files is similar, there are stark differences too between them. Techspirited resolves all the confusion between MSI and EXE files once and for all.
Padmini Krishna
Did You Know?
Although files with a .exe or a .msi extension are Windows files, certain techniques can be used to run them on Mac OS X too, such as dual-booting (simultaneous operation of both Windows and OS X), virtualization (running Windows on a virtual machine from inside OS X), or by the emulation of Windows (by making use of a software like Wine or Crossover Mac).

EXE (short for executable) files have made frequent appearances in the Microsoft file system right since the days of MS DOS. The first thing that comes to mind when one sees an EXE file is that running it will probably install the associated program on their computer. Actually, this is a widespread misconception because the functionality of EXE files is not restricted merely to installation.
But on the other hand, files of the MSI format have only one role, and that is program installation. In fact, the MSI extension is an acronym for Microsoft Installer, the former name of the Windows Installer program. In spite of being distinctly different, the MSI and the EXE file formats have a lot in common, and therefore, it is natural that Windows users often confuse the two.
However, as an aspiring software developer, or even for the purpose of enriching one's knowledge so as to avoid committing blunders regarding these two formats, it is imperative to clearly understand how they differ from each other.

MSI and EXE File Formats Compared

Definition and Description
.EXE
  • A file with a .EXE extension, as is mentioned above, is an executable file, which means that it contains lines of instructions or code, which can directly be understood by the Windows OS (or in simple words, it is a program that runs). 
  • All kinds of application software require respective EXE files, which contain information about those processes that need to be executed, in order for them to be installed, and subsequently run.
  • The various Windows system files and host processes contain a number of tasks that need to run, and therefore, EXE files are ideal for this role. However, if an application program is more complex than a bunch of tasks, and involves many lines of code, the need to store data, etc., (for example, a simple computer game), then too, an EXE file would be up to the task.
  • The EXE format is versatile to the level that it is indispensable to the Windows file structure.
.MSI
  • On the contrary, the MSI file format is strictly limited to the functionality of Windows Installer.
  • An MSI file is a compressed package of installer files, which contains all the information pertaining to adding, modifying, storing, or removing the respective software. 
  • The information contained in an MSI file may include data, instructions, processes, and add-ons that are required for the application to work normally, including registry and/or cached data.
  • Software developers opt for the MSI file format as opposed to one with a .EXE extension while creating the installer for their applications, because:
  1. It is incredibly simple to create one;
  2. It reduces their overheads in terms of time/coding effort;
  3. The latest version of Windows Installer offers a number of benefits to both the user and developer. 
Similarities and Differences in Handling Program Installation
.EXE
  • EXE files are not restricted to any format (unlike MSI files, which are MS-SQL databases in office-style binary). They may be script-based, written in native code or .NET Bytecode, or they too may be of the database type, depending on their application.
  • EXE files contain data that can be used both to install as well as to run the application program. Apart from the executable program code, EXE packages also contain what are known as resources―bitmaps, icons, and other-format image files that play a role in the Graphical User Interface (GUI) of the executable program. 
  • No standard or default GUI is provided to software developers wishing to create an EXE installer file, and therefore, they have full freedom to design it as they wish. Mostly, it is the developers of computer games who use the EXE platform for this purpose, and that is why the installer pages for these kinds of software are interactive and colorful.
  • An EXE installer, however, does not have the ability to remember a user's choices or to complete the installation independently. Users are regularly prompted to click on buttons like NEXT or OK if they wish to proceed to the next step of the installation process. Also, EXE files always install the full software, as they do not have the capability to perform 'installation on demand', a characteristic feature of MSI files that is explained in detail in the section below.
  • Alternatively, an EXE package may contain in it an MSI file for the installation of the program. If such an EXE file is run with the intention of program installation, the files in the inherent MSI package will be used for the installation. The EXE file by itself may either be just the capsule, or it may be the executable program for the installed software. 
.MSI
  • A Windows Installer package, or an MSI file, is a database that contains all the prerequisites to install a program on the computer.
  • The beauty of the MSI format is that it is compatible across the various editions of the Windows OS, as well as the different versions of Windows Installer, thanks to the MSI Redistributable File―a part of the package that exists for the sole purpose of bridging this gap. Hence, using the MSI platform gives software developers a larger audience for their application programs as well as standardization.
  • The Windows Installer provides a default standard GUI for the installer, which is customizable to some extent, and hence, developers need not bother about creating one from scratch.
  • Users are offered the privilege of least priority, an advantage which was first introduced in Windows Installer 4.0. (Prior to this, to run a Windows Installer package, one needed to be logged in as the computer's administrator. Now, the rule can bypassed, and proxy installation can be done.) 
  • The feature that truly sets MSI-format files apart from their EXE counterparts, is their ability to install software on demand. This means that rather than installing the full program, they transfer links and other essential data to the user's computer, and actually install the software only the first time it is run.
  • Even if a full installation is required to be carried out, MSI files have the ability to perform unattended installation, keeping in mind the user's choices or keystrokes at the beginning. It does not keep prompting users to click the corresponding button if they wish to move ahead in the installation process.
  • For an MSI package to run, and for the compressed files that it contains to be extracted, an EXE file called MSIEXEC.EXE is always required. This file acts like a sort of bootstrap program, or engine, that the MSI file takes the help of, so that the processes of data retrieval and program installation can be completed. MSIEXEC.EXE is also responsible for running the MSI Redistributable File in case it cannot find the required version of Windows Installer. 
It is clear that the circle of program installation is complete only with both an MSI and an EXE file.
While an EXE file itself has the ability to perform installations, it has its limitations and cannot offer developers and users the sophistication that comes with using the Windows Installer program. At the same time, however, all programs do require an EXE file to execute their processes so that they may run.
The process of installation too, irrespective of the kind of installer package being used―in fact, even for MSI files―requires an EXE file to play the role of the Windows Installer Engine, which begins all the associated tasks.
This was our in-depth comparison and analysis of the two vital Windows file formats. Do leave a comment if you still have an unanswered doubt regarding either of them.