Inno Setup is a free installer for Windows programs. First introduced in 1997, Inno Setup today rivals and even surpasses many commercial installers in feature set and stability.
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Inno Setup

Copyright (C) 1997-2018 Jordan Russell. All rights reserved.
Portions Copyright (C) 2000-2018 Martijn Laan. All rights reserved.
For conditions of distribution and use, see LICENSE.TXT.

Source code README

  1. Getting Started

  • Obtaining sources

    First you need to download the sources from Github. From the command line do:

    > git clone is
    > cd is
    > git submodule init
    > git submodule update

    If you don't have the Git client (git), get it from:

    To update your sources from the command line do:

    > git pull
    > git submodule update

    To be able to contribute to Inno Setup, clone your own fork instead of cloning the main Inno Setup repository, commit your work on topic branches and make pull requests. See

  • Install Borland Delphi

    Unicode Inno Setup:

    We compile all of Inno Setup's projects under Delphi 2009 with Update 3.

    Newer Delphi versions should also work but will lead to significantly larger files.

    To work with the Delphi 2009 IDE under Windows 8.1 you need these two things to make it work well: (md5sum: 545fc506c0614cf7a3339a7acb5217dc) (md5sum: c9598cf14452dd08987c5aec23d04f7d)

    Non Unicode Inno Setup:

    We compile all of Inno Setup's projects under Delphi 2.01, with the exception of Compil32 which is compiled under Delphi 3.02 (for the better Far East character set support), and Inno Setup Preprocessor's ISPP which is compiled under Delphi 7.

    Delphi 2.01 is used for the main projects because its VCL has a significantly smaller code size footprint than the later versions.

    If you do not have access to these old versions of Delphi, you should be able to compile the projects on later versions, however complete compatibility is NOT guaranteed. We try to make Inno Setup compilable on the later versions when possible, but do not have the resources to test every change on every Delphi version.

  • Install Microsoft MSXML

    Install Microsoft MSXML 4.0 SP2 if you haven't already done so. See

    If you are not sure whether you have MSXML 4.0 SP2 already, check for a file named msxml4.dll in your Windows System directory with a version number of 4.20.9818.0 (or later).

    Note: Microsoft MSXML is only needed to be able to compile the help files.

  • Install Microsoft HTML Help Workshop

    Install Microsoft HTML Help Workshop if you haven't already done so. See

    Note: Microsoft HTML Help Workshop is only needed to be able to compile the help files.

  • Building

    To build all files run build.bat and follow the instructions.

    To just compile Inno Setup run compile-unicode.bat for Unicode Inno Setup or compile.bat for Non Unicode Inno Setup and follow the instructions.

    To just compile the Inno Setup help file and its web version run ishelp\compile.bat and follow the instructions.

    To just compile the Inno Setup Preprocessor help file and its web version run Projects\Ispp\Help\compile.bat and follow the instructions.

  1. Delphi 2.0x users ONLY

Before you can successfully compile the projects in Delphi 2.0, you must do two things:

  1. Component Installation

If you intend to view or modify the Setup project's forms, you must install the following component units, which can be found in the Components directory.

  • BidiCtrls
  • BitmapImage
  • FolderTreeView
  • NewCheckListBox
  • NewNotebookReg
  • NewProgressBar
  • NewStaticText
  • PasswordEdit
  • RichEditViewer

If you intend to view or modify the Compil32 project's forms, you must additionally install the following components. (Like the Compil32 project itself, these require Delphi 3 or later.)

  • DropListBox
  • NewTabSet

If you only want to edit code, then you may skip installation of the components, and choose "Cancel" if the Delphi IDE tells you a class can't be found.

  1. Overview

Inno Setup consists of seven projects:

Compil32 - This is the GUI front-end for the compiler. Compil32 does not do the actual compilation itself; it relegates it to ISCmplr.dll. If the ISCmplr project is changed, you normally don't need to recompile Compil32 since it's essentially a text editor, and is not affected by internal changes to the compiler.

ISCC - This is the command-line front-end to the compiler. Like Compil32, it depends on ISCmplr.dll to do the actual compiling.

ISCmplr - This is a DLL which is loaded by Compil32 and ISCC to compile scripts. The actual compiler code is in Compile.pas. See CompInt.pas for the various structures and function declarations used to interface to the DLL.

Setup - This is the actual "Setup" program. It displays the wizard, and performs all (un)installation-related tasks.

SetupLdr - This is the "setup loader." It self-extracts a compressed Setup program into the user's TEMP directory and runs it from there. It also displays the "This will install..." and /HELP message boxes.

ISPP\ISPP - This is a DLL implementing Inno Setup's preprocessor interface

How do the projects link together?

  • ISCmplr, ISPP, Setup, and SetupLdr share the unit Struct.pas. This unit contains various data structures and constants shared by the projects. If Struct.pas is changed, you usually will need to recompile ISCmplr, ISPP, Setup, and SetupLdr so that everything is in synch.

  • There are more units which are shared between projects. Search the 'uses' clauses of the projects and units if you aren't sure if a project uses a particular unit.

  • The ISPP help file uses various copies of other Inno Setup files. To synch these run synch-isfiles.bat.

  1. Source code tips

  • If you modify the Setup or SetupLdr projects and want to be able to compile your installations with the new code, you'll need to copy the new EXE file(s) to the Setup Compiler directory under the extension .E32.

  • When debugging the Setup project you should set UseSetupLdr=no and OutputBaseFilename=setup in your script, and copy the resulting setup-*.bin files to the source code directory. This way you can simulate an actual installation while running under the Delphi debugger.

  • All of the forms in the Setup project, with the exception of Main.dfm, have Scaled set to False. This is because they dynamically scale themselves at run-time by calling a function named SetFormFont.

  • When a Cardinal-type variable is compared against a constant expression, why is a Cardinal cast sometimes used around the constant expression? For example:

        X: Cardinal;
        if X > Cardinal(1) then

    The cast is needed to work around a bug in Delphi 2 and 3 compilers: without it, a signed comparison is done.

  • A note for those curious: The Setup Compiler creates single EXE Setups by first creating the SETUP.EXE as usual, then concatenating the SETUP.0 and SETUP-1.BIN to the end of the SETUP.EXE, and finally modifying an internal data block in SETUP.EXE so it knows it's in "single EXE" form.

  • Starting with the 32-bit version of Inno Setup 1.12.7, the "StripReloc" utility is used to decrease the size of the Non Unicode .EXE and .E32 files.

    To download StripReloc, go to:

  • Delphi versions prior to 5 store .dfm files in a binary format. To be able to track changes to the forms using ordinary "diff" commands, .dfm.txt "mirrors" of the binary .dfm files have been created. Each time a .dfm file is modified, dfm2text is ran and both the .dfm file and the updated .dfm.txt file are committed.

    To download dfm2text, go to:

  • For compiler debugging purposes define STATICCOMPILER in CompForm.pas and STATICPREPROC in Compile.pas. The latter requires Unicode Inno Setup.

  1. Precompiled executables and libraries

The source code contains several precompiled executables and libraries:

Files\isbunzip.dll, Files\isbzip.dll - Compiled by Visual Studio 2005 from the bzlib directory in the Iscompress repository.

Files\isunzlib.dll, Files\iszlib.dll - Compiled by Visual Studio 2005 from the zlib-dll directory in the Iscompress repository.

Files\islzma.dll, Files\islzma32.exe, Files\islzma64.exe - Compiled by Visual Studio 2005 from the Projects\lzma2\Encoder directory.

Files\isscint.dll - Compiled by Visual Studio 2005 from Scintilla 2.22 source code with scintilla-2.22-patch.txt applied.

Projects_shfolder.res - shfolder.dll from a fresh install of IE 5.5 SP2 on NT 4.0 stored in a compiled resource file. Note: this file is normally not actually used by Setup.

Projects\Helper\x64\Release\Helper.exe, Projects\HelperEXEs.res - Compiled by Visual Studio 2005 from the Projects\Helper directory and then stored in a compiled resource file.

Projects\LzmaDecode\LzmaDecodeInno.obj - See Projects\LzmaDecode\compiling.txt.

Projects\lzma2\Decoder\ISLzmaDec.obj, Projects\lzma2\Decoder\ISLzma2Dec.obj - See Projects\lzma2\Decoder\compiling.txt.

ishelp\ISHelpGen\ISHelpGen.exe - See ishelp\ISHelpGen\compile.bat

Examples\MyProg.exe, Examples\MyProg-x64.exe - Compiled by Visual Studio 2005 from the Examples\MyProg directory.

  1. Inno Setup-specific editing guidelines for the help files

  • When mentioning something the user would type in a script, e.g. "MinVersion", surround it by <tt></tt> so that it's displayed in the Courier New font. This is a convention used throughout the help file. Example: <tt>MinVersion</tt>