App Categories
Windows uses the term "app" for several types of software. Store apps, desktop programs, runtime libraries, and remnants of removed software require different handling. O&O AppBuster identifies each type so that you can choose the appropriate action.
O&O AppBuster sorts everything it finds into categories and shows the category in the Type column and in each app's properties. This page is the map; the following pages describe each category in detail.
The categories at a glance
| Category | What it is | Removable | Page |
|---|---|---|---|
| Windows App | Modern app from the Microsoft Store (UWP / MSIX) | Yes | Windows apps |
| Store | A Store app that is registered on the PC but not installed for you | Install it | Windows apps |
| Staged app | Package files are on the PC but no user has it installed | Yes | Windows apps |
| Desktop App | Classic Windows program (Win32 / MSI) | Yes, by its own uninstaller | Desktop apps |
| Windows App (hidden) | Provisioned on the PC but not visible in your Start menu | Yes, or install it | Hidden apps |
| System App | A component Windows itself needs | No | System and framework apps |
| Framework App | A runtime that other apps depend on | No | System and framework apps |
| Orphaned App | Leftover data folder of an uninstalled Windows app | Yes, cleaned up | Orphaned apps |
| Orphaned Desktop App | Registration of a desktop app whose files are gone | Yes, cleaned up | Orphaned apps |
| Defect App | Still installed, but Windows can no longer uninstall it | Yes, cleaned up | Defect apps |
Two dimensions: what it is, and what state it is in
It helps to read the categories as two questions.
What kind of software is it?
- A Windows app is managed by the Windows package system. It can be removed per user, for all users, or from the machine, and it can be brought back.
- A desktop app is managed by its own installer. Removing it means running that installer's uninstall routine. There is no per-user removal and no way to bring it back except its setup file.
What state is it in?
- Installed — normal. It is there, it works.
- Installable / Staged — the files are on the PC, but nobody is using them.
- Orphaned — the app is gone; only traces remain.
- Defect — the app is there, but its installer infrastructure is broken, so Windows cannot remove or repair it.
- Unremovable — Windows depends on it.
How the categories are found
O&O AppBuster does not simply read the Windows Apps & features list. It enumerates several sources and reconciles them:
| Source | What it contributes |
|---|---|
| Windows package manager | Windows apps for the current user and for the machine |
HKLM\...\CurrentVersion\Uninstall (64-bit and 32-bit views) | Machine-wide desktop apps |
HKU\<SID>\...\CurrentVersion\Uninstall for every loaded profile | Per-user desktop apps of all logged-on users |
HKCR\Installer\Products | Windows Installer product registrations, including ghost entries |
%LocalAppData%\Packages | Data folders of Windows apps, including leftovers |
Desktop apps are enumerated before Windows apps on purpose. Some programs — Visual Studio Code and TortoiseGit are typical examples — are installed by an MSI but also register as a Windows package. Scanning the registry first means such an app is classified as the desktop app it really is, and the package information is merged into that one entry instead of producing a duplicate.
Registry access during the scan is read-only. Only a removal writes to the registry.
Newly discovered apps
Independently of these categories, O&O AppBuster remembers which apps were on the PC the last time you used it. Anything that has appeared since is flagged as newly discovered — a category of time, not of kind.
Where to start
If you just want a tidier PC, you only need two categories:
- Windows apps with a remove recommendation — preinstalled extras, safe to go.
- Desktop apps you no longer recognise — check them individually, then remove them.
The remaining categories are for specific situations: hidden apps when you want an app back, orphaned and defect apps when an earlier uninstallation left a mess, and system and framework apps purely for information.