How can I set the default file format in the Delphi IDE to UTF8?

In fact this blog post from 2004 mentions a hidden IDE option. It states that you can set a default file filter in the registry to make UTF-8 the default encoding in Delphi 8. This still works under Tokyo! Clearly, you have to adapt the path of the registry key to recent versions like this:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Embarcadero\BDS\19.0\Editor]
"DefaultFileFilter"="Borland.FileFilter.UTF8ToUTF8"

After setting this value Delphi will encode new units in UTF-8 with BOM.

AFAIK, there is no IDE-wide setting for specifying the default file format.

If you install UTF8ize Plugin (english translation of his page & latest version) to your IDE, when you edit any file within the IDE, the plugin set the file's codepage to UTF8 automatically.

(FYI: The author creates many useful plugins. I posted some of his plugins with image here, but my post was deleted by the modelator. I just wanted to know his useful plugins, but yes, it's off topic here. sorry.)

Right-click on your source code in the Delphi 2009 IDE, and select File Format. Then choose UTF-8. Hope that helps.