Can Inno Setup respond differently to a new install and an update?

Question

My InnoSetup script opens a web page (with the user\'s default browser) at the end of the install process:

[Run]
Filename: http://example.com; Flags: shellex         


        

Answer 1

The answer by @AndreasRejbrand won't work, if user chooses to install the executable to a different location than the last time.

You can query installer-specific Inno Setup registry keys:

#define AppId "your-app-id"
#define SetupReg "Software\Microsoft\Windows\CurrentVersion\Uninstall\" + AppId + "_is1"
#define SetupAppPathReg "Inno Setup: App Path"

[Setup]
AppId={#AppId}
...

[Run]
Filename: "https://www.example.com/"; Flags: shellexec; Check: not IsUpgrade
...

[Code]

function IsUpgrade: Boolean;
var
  S: string;
begin
  Result :=
    RegQueryStringValue(HKLM, '{#SetupReg}', '{#SetupAppPathReg}', S) or
    RegQueryStringValue(HKCU, '{#SetupReg}', '{#SetupAppPathReg}', S);
end;

For an example how to use IsUpgrade in [Code] section, see
Excludes part of Code section in ssPostInstall step if installation is update in Inno Setup

Check this is your "AppId" contains a left-curly-bracket:
Checking if installation is fresh or upgrade does not work when AppId contains a curly bracket

Answer 2

Yes, this is easy to do with scripting.

Just write

[Run]
Filename: "http://example.com"; Flags: shellexec; Check: NotAnUpdate

procedure CurPageChanged(CurPageID: Integer);
begin
  if CurPageID = wpInstalling then
    IsUpdate := FileExists(ExpandConstant('{app}\TheFileNameOfMyApp.exe'));
end;

function NotAnUpdate: Boolean;
begin
  result := not IsUpdate;
end;