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Lazarus Auto-Updater


  • LazAutoUpdater is a visual drop-in component for the Lazarus/FPC IDE to make updating your application easier and smarter.
  • LazAutoUpdae downloads via a background thread so the user can continue using your app without interruption
    • This means for example, your app can 'check for updates' at startup without the app becoming unresponsive.
  • It is aimed at Lazarus Windows and Linux developers who host their project in SourceForge or GitHub.
  • Drop-in the component, set one property (your sourceforge project name, ot GitHub properties) and call one simple method:
    • LazAutoUpdate.AutoUpdate
  • You (the developer) have plenty of control over how the component behaves, yet it is simple to use.
  • End-users see the updating process as simple and transparent
  • Tested and developed in Windows 10 64/32-bit and Linux Mint 64/32-bit

lauobjinsp1.jpg lauobjinsp2.jpg


  • LazAutoUpdate source code can be downloaded from the SourceForge project site
  • The Lazarus OnlinePackager also contains LazAutoUpdate


  • Download the Windows setup file or the linuxbinaries zip
  • Windows: Install, Linux: Unzip in a spare folder
  • Use the UpdatePack to make and distribute your update files
  • Use the LazAutoUpdate component to add update functionality to your Lazarus app
    • You will need to distribute updatehm<os>(.exe) with your application for LazAutoUpdate to work correctly


  • Drop the component onto the main form of your application
  • Set the SFProjectName property to your SourceForge project name (the same text as appears in the URL for your project page)
  • or.. Set the GitHub properties:
    • GitHubProjectname: Username or Organisation
    • GitHubRepositoryName: Your project/repository
    • GitHubBranchOrTag: 'master' for the root or the GitHub Branch name or Tag name
  • In both cases set the UpdatesFolder to the location of your update files (you can leave it blank)
  • Then let the component take care of the details. Just use (perhaps as a Help menu item 'Check for updates')
  • Decide if you want your app to check for updates on startup. If so, in your form.activate handler:
If LazAutoUpdate1.NewVersionAvailable Then
      MessageDlg(Application.Title, 'A new version of ' + Application.Title +
        ' is available.' + LineEnding +
        'Click ''Check for new version'' in Help menu to update', mtConfirmation,
        [mbOK], 0);
  • Give the user a chance to update the application. Here's some sample code:
LazAutoUpdate1.SFProjectName := 'lazautoupdate';
If LazAutoUpdate1.NewVersionAvailable Then
  If LazAutoUpdate1.DownloadNewVersion Then
    If MessageDlg(Application.Title, 'Download Succeeded.  Click OK to update',
      mtInformation, [mbOK], 0) = 1 Then
    ShowMessage('Sorry, download of new version failed')
  ShowMessage('Sorry, no new version is available');
  • You don't want the user to close your application in the middle of an update! Use this code in the Form.CloseQuery handler:
If LazAutoUpdate1.DownloadInProgress Then
  CanClose := False;
  ShowMessage('Please wait. Download is still progress.');
  • This gives you the 'bare bones' of the update code for your application. As you can see, it's all pretty automatic and simple.

Deploying your Application with LazAutoUpdate

  • Use UpdatePack to manage the process.
    • UpdatePack is a GUI application that makes the update files accurately and quickly, and even gives you the corresponding LazAutoUpdate code for your app.
    • It uses 'profiles' that enable you to deploy future updates by simply updating the version number and clicking 'Create Update Pack'.
    • Your app users will benefit from having the latest version of your software always available.


Using auOtherSourceFilename and auOtherSourceURL

  • When ProjectType is set to auOther, LazAutoUpdate will use these properties for all the Methods. See example application in the SVN archive.

Making a generic installer/updater

  • Once a LazAutoUpdate component has been dropped onto a form, it can be used for multiple updates, downloads etc.
  • For a generic installer/updater you need to set:
    • VersionsINIFilename
    • ZipFilename
    • AppFileWithPath
    • AppVersion
  • By setting these properties dynamically (perhaps via a menu) you can enable the user to update multiple applications hosted on a SourceForge/GitHub project site (or any site using auOther settings - see above)
  • Here's example code to use LazAutoUpdate to download then run an application.
  • The zipped files for the application (including 'whatsnew.txt') and the file 'mywizzyapp.ini' are located in the /updates subdirectory of the SourceForge project 'mywizzy'
  • The executable 'updatehm.exe' is in the same directory as your updater app
  • The user would download a small InnoSetup installer with just the online installer/updater, which in turn would download the main application and supporting files.
procedure TForm1.Button1Click(Sender: TObject);
Application.Title:='My whizzy app';
If LazAutoUpdate1.DownloadNewVersion then

Public Methods List

  • Function NewVersionAvailable: Boolean;
  • Function DownloadNewVersion: Boolean;
  • Function UpdateToNewVersion: Boolean;
  • Procedure ShowWhatsNewIfAvailable;
  • Procedure AutoUpdate;

Non-published Properties list

  • GUIOnlineVersion: String
  • ModuleOnlineVersion: String
  • ReturnCode: Integer
  • DownloadInprogress: Boolean
  • AppFileWithPath: String
  • AppVersion: String
  • LastError: String;

Deploying multiple updates in a single project

  • By default, the ZipFilename is the same as your application, but you can set it to a unique value, and deploy it to your Online Files/updates irectory
  • Each application to be updated should have a unique name for the versions.ini file. Set the VersionsINIFilename property.

In case the download takes to long

  • VersionCountLimit property determines how long LazAutoUpdate will check for a new version before timing out.
  • DownloadCountLimit property determines how long LazAutoUpdate will try downloading the new version before timing out.


The format is as follows:

;LazAutoUpdate versions file
  • The file is small so that it is very quick to download

Source Code and latest versions


Windows 10

  • Windows 10 security will not allow a non-admin user to update applications from the internet (unless it's a Windows Store App). This is a sensible policy in my opinion, and LazAutoUpdate adheres to it.
    • If an 'ordinary user' tries to update an app using LazAutoUpdate, all will go smoothly until the final 'Update app' phase. At that point LazAutoUpdate will pop up a dialog informing the user that an administrator account is needed for the actual update.
    • For an 'admin user', LazAutoUpdate will pop up a UAC dialog (the same as any installer) and proceed upon clicking 'yes' to do the update.
    • If you wish to circumvent this (perhaps with a manifest) LazAutoUpdate has the public property 'WindowsAdminCheck' which you can set to FALSE and avoid the dialog.


  • Linux will do the update without even showing the update console, and the user gets a seamless experience.


(Technical explanation)

The Laz AutoUpdater workflow for updating a running application is as follows:

  • App downloads a small 'version.ini' file from sourceforge or github with version info (it can do this at start-up)
  • App compares with its own internal version
  • If new version available
    • App deletes any contents of local /updates folder
    • App downloads then unzips it from the web into a local /updates folder
  • App uses TAsyncProcess to start the console updater.exe, passing it the name of the file to be updated in the command line
  • updater.exe copies a downloaded 'whatsnew.txt' into the App folder and enters Sleep for a few seconds
  • Meanwhile App has entered loop checking whether a 'whatsnew.txt' file has been copied into it's directory
  • App detects 'whatsnew.txt' and Closes. (in other words the TProcess has started successfully)
  • Updater copies /updates/UpdatedApp to App directory.
  • Updater uses TProcess to start the updated app
  • On Form.Show, App displays 'whatsnew.txt' then deletes it

The User sees:

  • Dialog: 'There's a new version of xxx available. Would you like to download it?' Yes/No
  • If Yes clicked:
    • Download happens in the background (via a background thread) Optional 'download counter' is shown to indicate progress.
    • User is prevented from closing the app whilst the download is in progress (in Form.CloseQuery)
    • Dialog: 'The update is downloaded. Click OK to install it and restart xxx now' OK
    • User clicks OK
    • A console (DOS window in Windows) opens automatically and the Application closes. The console says 'Please wait updating xxx'
    • After a couple of seconds the console disappears, and the new version of the App starts
    • As soon as the main window is shown, a 'What's New' info box is shown with an OK button
    • User clicks OK button, and never sees the info again