electron-builder appId to uninstall GUID calculator

Type an appId and see the exact Windows installer identity that electron-builder's NSIS target derives from it: the GUID, the uninstall and install registry keys, and the single-installer mutex. Everything is computed in this page. There is no network request of any kind.

Behaviour reimplemented from app-builder-lib 26.15.3. Source read 2026-09-05.

Why this matters. The uninstall and upgrade lookup is keyed on the GUID, and the GUID is derived from the appId string alone. Two builds that agree on product name, publisher, version and file layout but differ in appId write different uninstall registry keys, so the new installer does not find the old install and does not upgrade it. The install directory, by contrast, is derived from entirely different fields, so it can stay identical while the identity underneath it changes.

Derived installer identity

Every row is labelled with the input it is derived from.
NSIS define	Value	Derived from

What this page does not claim

Setting nsis.guid explicitly bypasses the derivation entirely. The NSIS target reads options.guid first and only falls through to the UUID v5 derivation when it is absent. If you set it, every GUID row below is irrelevant to your build.
APP_FILENAME, PRODUCT_FILENAME and the updater cache directory are not derived from appId. They come from name, productName and executableName. Only the GUID, the uninstall key, the install registry key and the installer mutex trace back to appId.
This tool computes installer identity. It has nothing to do with code signing, publisher identity, notarization or certificates, which are a separate subsystem.
A second uninstall key, UNINSTALL_REGISTRY_KEY_2, is emitted only when the uninstall app key differs from the GUID. That happens only for a hand-set nsis.guid containing a backslash, because a derived v5 GUID is hexadecimal and hyphens and can never contain one. It is omitted from the table above for that reason.
This project is independent and unaffiliated with electron-builder, its maintainers, or Microsoft.

Self test

The derivation is only worth reading if the primitives underneath it are right. This runs published SHA-1 test vectors, known UUID v5 pairs, filename sanitisation cases, and one positive control that must always fail. A checker that has never produced a failure has not been tested.

Not run yet.