Extension Icons

A Windows 11 app that gives every file extension a consistent, correct icon — independent of whichever app currently claims it.

Early development

The problem

Windows ties an extension's icon to whoever last claimed it.

Windows resolves a file extension's icon through whichever app last registered itself as that format's handler. In practice, .htm and .html show up as “Edge documents,” and general-purpose formats like .xml, .csv and .json are routinely rebranded with the icon of whatever app last installed itself as their handler — even when several unrelated apps can open the same format. Installing a new, “aggressive” application can silently take over icons and associations for extensions it has no special claim to.

What it does

The icon is a property of the file type, not of whoever owns it today.

Distinct icons per type

Keeps a consistent icon for common extensions regardless of which application currently owns the association.

Capability-aware

Recognizes which installed applications can handle a given extension, not just which one is currently the default.

Per-action defaults

Choose, per file type, which application should open, edit, text-edit, or browse a file.

Fix mode

Reverts icons and associations to a previously saved state — useful right after an aggressive install.

Themes

Supports sets of file-type icons, including themes downloaded from community repositories.

User scope first

The MVP writes only to your own HKCU associations — no admin prompt required.

Tech stack

Language	C#
Runtime	.NET 8
UI	WPF, MVVM
Platform	Windows 11
Integration	Windows Registry & Shell APIs (`HKEY_CLASSES_ROOT`, per-user `UserChoice`)
Localization	English and Spanish, planned for v1.0

Roadmap

Done

Phase 0 · Foundation

Validated the icon-override mechanism live on Windows 11, then built the Core registry/shell abstraction layer with fake providers and unit tests.
Next

Phase 1 · MVP (v0.1)

Extension inventory with a built-in catalog, a read-only inventory UI, per-user icon overrides, and one-click “fix mode” revert.
Later

Phase 2 · v1.0

Per-action default-app assignment, an elevated helper for machine-wide changes, icon theme import/export, an installer, and the English/Spanish UI.
Later

Phase 3 · Wishlist

Content-based format recognition beyond the extension, per-file icons, a community theme repository, and a background watcher for icon hijacks.