Identifiers in Web Apps (WebAPKs and TWAs)

This document clarifies the differences between various identifiers used in the context of Web Apps (WebAPKs and TWAs) on Android.

Identifiers Breakdown

Identifier	Scope	Source	WebAPK	Standard TWA	TWA Installer (Auto-Minted)
Manifest ID	Web App	Web Developer (in manifest.json)	Used to identify the PWA; influences package name.	Optional in manifest; does not influence package name automatically.	Used to identify the PWA; influences package name.
Package Name	Android OS	Generated by Server/Installer or specified by Developer	org.chromium.webapk.<hash> (hash derived from Manifest ID/URL).	Manually specified in Android project (e.g., com.example.app).	com.android.webapp.<hash> (hash derived from Manifest ID/URL).
Android UID	Android OS	Assigned by Android at install time	Unique per installation instance (varies by user profile).	Unique per installation instance.	Unique per installation instance.
Android AppId	Android OS	Assigned by Android at install time	Constant across users for the same app package.	Constant across users for the same app package.	Constant across users for the same app package.
App Name / Label	User Visible	Web Manifest or Android Project	Derived from name or short_name in manifest.	Specified in Android project AndroidManifest.xml.	Derived from name or short_name in manifest.
Origin	Web	Web URL	The web origin (e.g., https://example.com) the app is locked to.	The web origin the app is locked to.	The web origin the app is locked to.
Domain	Web	Derived from Origin	eTLD+1 (e.g., example.com) used for broader data clearing scopes.	Used for broader data clearing scopes.	Used for broader data clearing scopes.

Detailed Concepts

1. Android UID (User ID)

• Scope: Android Operating System.
• Type: Integer.
• Definition: UID = UserId * 100000 + AppId.
• Purpose: Used for process isolation, security sandboxing, and permission management.
• Sharing: Can be shared between packages that request it (via sharedUserId in AndroidManifest.xml) and are signed by the same key.

2. Android AppId

• Scope: Android Operating System.
• Type: Integer.
• Source: Part of the UID assigned by the Android system.
• Purpose: Identifies the application within the user's space. It is NOT derived from the Web Manifest.

3. Web Manifest ID

• Scope: Web Application (PWA).
• Type: String (defined in manifest.json).
• Source: Provided by the web developer.
• Purpose: Uniquely identifies the PWA to the browser. It allows the browser to track the app even if the start URL or manifest URL changes.

Summary Flow

Web Manifest ID -> (influences) -> Android Package Name -> (installed by Android) -> assigns Android UID (containing AppId).