How to automatically update an application installed with Inno Setup

Inno Setup does not have any built-in mechanism for implementing automatic updates.

You need to implement that yourself:

• Make your application check for new versions (against your application webpage?). E.g. on startup (on a background thread?)
• If the application detects a new version, make it download an installer to a temporary location.
• Make the application execute the downloaded installer. You can make the installer run in silent mode (/silent switch). The application should close itself, to unlock any files it is using, to allow files update.

This approach will need the update installer to prompt for Administrator privileges. If you need the update to proceed completely seamlessly, you will have to implement a service. For that, see Deploying application with .NET framework without admin privileges.