Installing Lazarus on Windows

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Revision as of 23:58, 19 January 2021 by Wp (talk | contribs) (First start of the IDE: fppkg configuration error)
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This article applies to Windows only.

See also: Multiplatform Programming Guide

Using the Windows Installer

By far the easiest and most common way to install Lazarus on Windows is to go to the official Lazarus SourceForge download site select an appropriate combined FPC/Lazarus installation package, download the latest release and launch the installer.

The current releases of the Windows Lazarus installer packages install very easily, and should work 'out-of-the-box'.

Do not install into the standard program folder c:\Program Files because access to it is restricted. Moreover, it is recommended to avoid spaces in the folder name because it may confuse some tools used by Lazarus.

If you already have another Lazarus version on your system it is recommended to keep the old version and to keep it separate from the new installation. For this purpose Lazarus offers to write its configuration files into a specific directory so that both versions can coexist. See section Preparation for the first start below.

Upgrading can be as simple as downloading the new installer and running it. You will be taken through a typical Windows installation wizard to install the FPC compiler and FPC source within the same directory structure as Lazarus IDE, and Lazarus should launch and operate without significant problems, provided you have uninstalled any previous version of Lazarus and/or FPC which was not installed with a recent version fo the Windows installer (older installations can often be found in the C:\pp directory).

You can also use a Lazarus Snapshot. For download locations see Lazarus Snapshots Downloads.

Tip: It's perhaps a good idea to reboot your Windows system after you have installed Lazarus and before you try to install additional Lazarus components such as zeoslib for example.

Installing Lazarus on a Portable USB Drive

It is even possible to install the whole Lazarus/FPC package on a portable USB drive (capacity at least 256 MB), for use in environments where you are not allowed to install software on your Windows workstation or where you haven't got administrator privileges. You do have to be a little careful about adjusting the paths in the compiler and environment options and the fpc.cfg file. It may also be necessary to keep the directory for test compilation on your portable drive.


A: This is what I do. It's relatively convoluted, but it's the best solution I've found. I have a "bin" directory on my USB drive, where I have several scripts and utilities installed. Inside that directory is a batch file called "setenv.bat" which sets an environment variable called THUMBDRIVE. It is set by using this command in the batch file:

set THUMBDRIVE=%CD:~0,2%

This is used in setenv.bat to set some paths to other things I have installed on the USB drive. I also have a link in the root directory of the thumb drive with this property:

%SystemRoot%\system32\cmd.exe /k bin\setenv

so that when I click on that link when the thumb drive folder is displayed after inserting it, it will open a command prompt at the thumb drive with the environment variables set from setenv.bat.

Also inside the bin directory is sed (the actual binary is one I obtained from the mingw distribution). So I created another batch file called fixlaz.bat which takes one argument, the drive letter which is currently in the Lazarus/FPC settings files that you want to change (note that this is the previous drive letter the last time you ran fixlaz.bat, not the current one of your USB drive which fixlaz.bat already knows). You will need to create this batch file to fit where you installed Lazarus in the root directory structure of the drive if you didn't install it directly in the root folder, and then repeat these lines also for the editoroptions.xml and fpc.cfg files (fpc.cfg is in the fpc bin directory, which might be buried deep in the lazarus folder):

copy %THUMBDRIVE%\lazarus\environmentoptions.xml %THUMBDRIVE%\lazarus\environmentoptions.bak
sed -e 's/%1/%THUMBDRIVE%/g' %THUMBDRIVE%\lazarus\environmentoptions.bak > %THUMBDRIVE%\lazarus\environmentoptions.xml

So to use it, I would type at the command prompt of the USB drive:

fixlaz G:

if "G:" was the previous drive letter used the last time I ran it. This will then scan the file(s) and replace "G:" with the current drive letter of the USB drive, which is in the %THUMBDRIVE% environment variable (after running setenv.bat). Note that you could write it to save the current drive letter in a separate file, so that you wouldn't have to remember it yourself the next time. But this works well enough for me right now.

Installing Lazarus from sources on Windows

The following instructions are for SubVersion, but there is also a Git mirror repository of Free Pascal Compiler and Lazarus. See Git mirror for details. You can also use git directly with SubVersion server using git-svn link. See Lazarus git-svn for details.

It is assumed that the following installation will go into a folder c:\Lazarus-trunk. Of course any other name can be used for it provided that it does not contain spaces or non-ASCII characters, and that the folder is fully writable for the user. This excludes from installing into c:\Program files.

Getting the Lazarus sources by using TortoiseSVN

The easiest way to work with svn is by using the TortoiseSVN application ( Install this application if you do not have it already. It adds short-cuts to the Explorer context menu from which you can work with svn easily.

To download the Lazarus trunk sources create folder c:\Lazarus-trunk and right-click on it in the Explorer. In the context menu open the command SVN Checkout.... Enter the URL of the SVN repository in the corresponding box. This is

Make sure that the Checkout directory box contains the directory in which you want to have the new Lazarus version (c:\Lazarus-trunk in our example). After pressing OK the source files are downloaded which will take some time.

Getting the Lazarus sources from the command line

Alternatively to TortoiseSVN you can also download the sources from the command line if you have the command line version of SVN on your system (

  • Open a command prompt window
  • Create a folder for the new Lazarus:
md c:\Lazarus-trunk
  • Change into this folder:
cd c:\Lazarus-trunk
  • Execute the svn command with the checkout option (or in short: co) and the repository URL as parameter. The last parameter is the destination directory which can be specified explicitely or by simply typing "." (because you made a cd to this directory in the preceding step):
svn checkout c:\Lazarus-trunk
  • If you want the sources of the fixes branch instead of trunk replace the trunk in the URL by fixes_n_m where n and m refer to the version number of the release version (e.g. fixes_2_0 for the fixes of Lazarus v2.0.x"
  • The download will take some time. Be patient.

Getting the Lazarus sources from a snapshot

You you do not want to use svn you can also download the Lazarus sources from one of the snapshot servers. But you should be aware that the snapshots are not built regularly and may be out of date.

Unzip the downloaded archive to the folder in which you want Lazarus to be installed, e.g. c:\lazarus-trunk.

Building Lazarus

Prerequisite for building Lazarus is that a recent FPC installation must be available. "Recent version" means:

  • FPC trunk or fixes
  • the current FPC release or
  • the previous release version.

You probably already have a Lazarus release installation on your disk - here you can find the FPC in the equally named folder of the installation directory. Make sure that the FPC version number is adequate. If not, install a newer Lazarus release (which is always recommended). Or, of course, you can also install an FPC separately.

You should also be aware that the bitness of the FPC determines the bitness of the Lazarus IDE and the bitness of the applications that you will create. So, when your fpc.exe resides in a folder i386_win32 the IDE (and your applications) will be 32-bit. When the folder is x86_64-win64 the IDE (and your applications) will be 64-bit.

  • Remember the full path to the folder containing fpc.exe and use it in the following batch file.
  • Change to the folder into which you downloaded the source files and create a batch file with the following content
set path=c:\freepascal\bin\x86_64-win64
:: Of course change this path variable to the path of your FPC compiler
make bigide
  • Executing this batch file will build a Lazarus containing all the basic packages, like in a release version. (Of course you must install any other third-party packages by yourself later.)
  • Since Lazarus trunk is not "stable" it may happen that the "bigide" version cannot be build due to an error in one of the standard packages. In this case it may be helpful to know that the basic IDE (with LCL only) can be build by using the make command without the bigide parameter:
set path=c:\freepascal\bin\x86_64-win64
:: Of course change this path variable to the path of your FPC compiler
  • Because the Lazarus IDE by default links to a dll-call "CreateToolhelp32Snapshot", which does not exist on the Win9x platform, the IDE will not run on Win9x out of the box. In order to make it run you have to rebuild the IDE with make -dWIN9XPLATFORM bigide.
  • Compilation will take some time again. At the end, the new IDE is ready, but you should not start it yet -- read the next chapter.

Preparation for the first start

Before you start the new IDE you should make sure that it does not interfere with your current other Lazarus installation(s). For this purpose you must have a separate directory for the Lazarus configuration files, maybe c:\LazConfigs\trunk. Lazarus writes is configuration settings to this folder if you open the lazarus.exe with the argument --primary-config-path=c:\LazConfigs\trunk, or shorter, --pcp=c:\LazConfigs\trunk. When this parameter is missing the configuration files are read from and written to the default folder in c:\users\<your_name>\appdata\lazarus which will very probably change settings of the other installation.

Since it is easy to forget this commandline parameter it is highly recommended to add a file lazarus.cfg to the lazarus installation folder in which the pcp parameter is listed. This is also to way how the Lazarus release versions handle secondary installations.

To summarize, before starting the new IDE for the first time create a file lazarus.cfg in the Lazarus installation directory (the one which contains lazarus.exe) with the following content (of course, the path must be changed according to the current situation):


Alternatively you can also start the IDE from the desktop short-cut which has the --pcp=... as an argument.

First start of the IDE

When you start the new IDE for the first time probably there will be an error message saying that the FPC and the debugger cannot be found. In this error dialog, navigate to the folder which you had used as the path to build the IDE, and select the fpc.exe. As for the debugger, navigate to the mingw folder of your Lazarus release installation (or install gdb separately) and select the gdb.exe. There may also be a message about an issue with the fppkg configuration - click "Restore fppkg configuration" to resolve this. If subsequent error messages appear they can be neglected.

Now the IDE will be happy and you can start using your new Lazarus trunk (or fixes) IDE.

Updating the installed version

It is the advantage of a version-control system such as svn that it is very easy to update the installed version to any subsequent changes.

  • If you used TortoiseSVN right-click on the installation folder of this Lazarus and select SVN Update from the context menu.
  • If you prefer the console change-dir to the installation folder and type svn update, or svn up

The download now is very fast because only the differences to the local installation must be fetched.

Then start the IDE, go to Tools > Build Lazarus with profile... and recompile the IDE. It may happen that compilation aborts with some error; in this case go to Tools > Configure Build Lazarus, select Clean all and Switch after building to automatically in the "Clean up" box, and click Build.

Help: The new IDE does not start.

In very rare cases the new sources contain a fatal error so that the IDE does not start successfully.

For this case you must know that the IDE always keeps a backup copy, called lazarus.exe.old. Simply delete the newly created lazarus.exe and rename lazarus.exe.old to lazarus.exe. Now you are back to work, at least with the old version.

Try the installation later again, usually such catastrophic bugs are soon detected, reported and fixed. You may want to right-click on the Lazarus installation folder and select SVN Show Log from the context menu to see the commit notes of the recent changes and to learn whether the bug already has been fixed.

What does the bigide make argument do?

The bigide make argument adds a bunch of packages to Lazarus that many find useful and cannot do without. The packages that are added are:

  • cairocanvas
  • chmhelp
  • datetimectrls
  • externhelp
  • fpcunit
  • fpdebug
  • instantfpc
  • jcf2
  • lazcontrols
  • lazdebuggers
  • lclextensions
  • leakview
  • macroscript
  • memds
  • onlinepackagemanager
  • pas2js
  • PascalScript
  • printers
  • projecttemplates
  • rtticontrols
  • sdf
  • sqldb
  • synedit
  • tachart
  • tdbf
  • todolist
  • turbopower_ipro
  • virtualtreeview

The above list is sourced from the [Lazarus source directory]/IDE/Makefile.fpc and may be subject to change.

Note that if you have not compiled your own Lazarus IDE with the bigide argument, you can install any of these packages yourself using the Lazarus IDE Package > Install/Uninstall Packages... dialog.

Multiple Lazarus installs

Please see Multiple Lazarus for details on having more than one Lazarus version installed on one system. We cover issues that can arise due to multiple Lazarus installs here, because they can also happen when installing over a previous version.


Troubleshooting details that should (hopefully) be applicable across platforms may be found in the article Installation Troubleshooting.

Lazarus FAQ

The Lazarus FAQ - Frequently Asked Questions - page is available here.

Installing old versions

See Installation hints for old versions

See also