> ## Documentation Index > Fetch the complete documentation index at: https://docs.go.gbgplc.com/llms.txt > Use this file to discover all available pages before exploring further. # Android Bridge SDK > Embed GBG GO identity verification journeys in your Android app using the GBGBridge SDK. GBGBridge is a lightweight Android library for embedding web-based identity journeys in native apps. It provides a type-safe messaging protocol so web content in an Android `WebView` can request native capabilities like camera capture, with the same wire protocol as the [iOS Bridge SDK](/docs/go-v2/developer-integration/sdks/ios-sdk). ## What GBGBridge enables * **Native capability access from web journeys**: Web-based identity flows can request camera capture and other device features through a standardized message protocol. * **Typed capability slots**: Declare support for document capture and selfie capture by setting handlers on built-in typed slots. The SDK handles result encoding, busy rejection, and capability query responses automatically. * **Bidirectional messaging**: Both the native host and the web content can send and receive structured messages, enabling real-time coordination. * **Capability negotiation with permission state**: The web journey can query which native capabilities are available — including camera permission status — before attempting to use them, enabling graceful degradation across environments. * **Works with Compose and the View system**: The SDK has no UI dependency. Compose hosts wrap a `WebView` in `AndroidView`; View-system hosts attach to a `WebView` from an Activity or Fragment. Typed slots expose a `StateFlow` for reactive UI binding. * **Extensible handler architecture**: Register custom capability handlers to fulfil any request type the web journey might send, alongside or instead of typed slots. ## Architecture at a glance GBGBridge sits between your Android app and the web journey, routing structured messages in both directions: ```mermaid theme={null} graph TB subgraph Host["Android Host Application"] BH[BridgeHost
message router] CH[Capability Handlers
camera · custom] WV[WebView
BridgeWebViewConfigurator] BH <--> CH BH <--> WV end Web["Web Journey (JavaScript)"] WV -- "evaluateJavascript
window.GBGBridge.receive" --> Web Web -- "postMessage
window.GBGBridge" --> WV ``` The web journey sends structured JSON messages to the native host via `window.GBGBridge.postMessage()`. The `BridgeHost` decodes each message, routes requests to registered capability handlers, and sends responses back by evaluating JavaScript on the WebView via `window.GBGBridge.receive()`. ## Quick start The minimum integration is a `BridgeHost`, a `WebView` attached to it and pointed at your journey URL, and a handler set on the document-capture slot: ```kotlin theme={null} import com.gbg.gbgbridge.core.BridgeHost import android.webkit.WebView import androidx.compose.runtime.* import androidx.compose.ui.viewinterop.AndroidView @Composable fun JourneyScreen(journeyUrl: String) { val host = remember { BridgeHost(hostVersion = "1.0.0").apply { // Declare document capture support by setting a handler documentCapture.handler = { request -> // Present your camera UI and return a result documentCapture.awaitCompletion() } } } AndroidView(factory = { context -> WebView(context).apply { host.attach(this) loadUrl(journeyUrl) } }) DisposableEffect(host) { onDispose { host.detach() } } } ``` Setting a handler on a typed slot automatically declares the capability as supported. `attach()` handles WebView configuration, bootstrap script injection, and message-channel registration. Capability query responses — including permission state — are built automatically from the slots you configure. ## Requirements | Requirement | Minimum | | ------------ | -------------------------------------------------------------- | | Android | API 24 (Android 7.0) | | compileSdk | 34 | | JDK | 17 | | Kotlin | 2.x | | Distribution | Maven Central (`com.gbg:gbgbridge-sdk`) | | Dependencies | kotlinx-serialization, kotlinx-coroutines, androidx.annotation | Install with a single Gradle dependency: ```kotlin theme={null} dependencies { implementation("com.gbg:gbgbridge-sdk:0.1.0-alpha01") } ``` ## Reference app A complete, runnable reference integration — including a companion server, capture screens with CameraX, and terminal-event handling — is available at [gbg-go-android-reference](https://github.com/gbgplc/gbg-go-android-reference). The [Tutorial](/docs/go-v2/developer-integration/sdks/android/tutorial) walks through it end to end. ## Documentation map | Document | Description | | ------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------- | | [Tutorial](/docs/go-v2/developer-integration/sdks/android/tutorial) | Build a complete Android identity verification app from scratch | | [Getting Started](/docs/go-v2/developer-integration/sdks/android/getting-started) | Step-by-step installation, setup, and first integration | | [Concepts](/docs/go-v2/developer-integration/sdks/android/concepts) | Architecture, mental model, terminology, and design rationale | | [API Reference](/docs/go-v2/developer-integration/sdks/android/api-reference) | Complete reference for every public type, method, and property | | **Guides** | | | [Embedding](/docs/go-v2/developer-integration/sdks/android/embedding) | Embedding the WebView in Compose and View-system apps | | [Messaging](/docs/go-v2/developer-integration/sdks/android/messaging) | Sending events, handling requests, and response patterns | | [Capability Handling](/docs/go-v2/developer-integration/sdks/android/capability-handling) | Registering handlers, capability queries, and environment negotiation | | [Capture Screens](/docs/go-v2/developer-integration/sdks/android/capture-screens) | Building capture UI with CameraX, the photo picker, and placeholders | | [Security](/docs/go-v2/developer-integration/sdks/android/security) | Security model, origin allowlisting, and transport safety | | [Troubleshooting](/docs/go-v2/developer-integration/sdks/android/troubleshooting) | Common issues, debugging techniques, and diagnostic tools | | [FAQ](/docs/go-v2/developer-integration/sdks/android/faq) | Frequently asked questions | | **Examples** | | | [Hello Journey](/docs/go-v2/developer-integration/sdks/android/examples/hello-journey) | Minimal integration — load a journey and display it | | [Two-Way Communication](/docs/go-v2/developer-integration/sdks/android/examples/two-way-communication) | Send events and handle requests bidirectionally | | [Advanced Integration](/docs/go-v2/developer-integration/sdks/android/examples/advanced-integration) | Custom config, lifecycle handling, error handling, capability checks | ## License GBGBridge for Android is published under the MIT license — see the [Maven Central listing](https://central.sonatype.com/artifact/com.gbg/gbgbridge-sdk) for distribution details.