Firebase-KMP-Kit
0.4.0indexedUnified Firebase Remote Config access through a single API, fetchAndActivate, typed getters, JSON export, simple initialize, optional auto-refresh and REST-backed local cache.
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🔥 Firebase KMP Kit
A Kotlin Multiplatform library that provides Firebase Services across all major platforms (Android, iOS, JS, WASM, Desktop) through a single, unified API.
Characteristics
Supported Targets
KMP Target Names
Dependency
// build.gradle.kts
kotlin {
sourceSets {
commonMain.dependencies {
implementation("io.github.razotron.firebase-kit:analytics:0.4.0")
implementation("io.github.razotron.firebase-kit:remote-config:0.4.0")
implementation("io.github.razotron.firebase-kit:messaging:0.4.0")
implementation("io.github.razotron.firebase-kit:performance:0.4.0")
implementation("io.github.razotron.firebase-kit:crashlytics:0.4.0")
}
}
}
Analytics - Common API
Android, iOS, JS, and Wasm expose Firebase.analytics for Firebase Analytics event logging:
// commonMain
Firebase.analytics.logEvent(
name = "purchase",
parameters = Bundle().apply {
put("item_id", "pizza")
put("quantity", 1)
put("price", 12.5)
put("is_featured", true)
}
)
Firebase.analytics.setUserId("user-42")
Firebase.analytics.setUserProperty("favorite_food", "pizza")
Firebase.analytics.setAnalyticsCollectionEnabled(true)
Firebase.analytics.resetAnalyticsData()
Bundle also supports serializable payloads via kotlinx.serialization:
// commonMain
@Serializable
data class PurchaseMeta(
val coupon: String,
val source: String,
)
Firebase.analytics.logEvent(
name = "purchase_meta",
parameters = Bundle().apply {
put("meta", PurchaseMeta(coupon = "SPRING", source = "banner"), PurchaseMeta.serializer())
}
)
Installation (only iOS targets)
// Change path to the 'xcodeproj' file and module with Firebase Kit dependency if needed and perform
XCODEPROJ_PATH="$(pwd)/iosApp/iosApp.xcodeproj" ./gradlew -p "$(pwd)" ':shared:integrateLinkagePackage'
Remote Config - Common API
All platforms share the same FirebaseRemoteConfig interface, accessed via Firebase.remoteConfig:
// Fetch latest config values from Firebase and activate them
Firebase.remoteConfig.fetchAndActivate()
// Read typed values by key
val flag: Boolean? = Firebase.remoteConfig.getBoolean("key")
val label: String? = Firebase.remoteConfig.getString("key")
val price: ? = Firebase.remoteConfig.getDouble()
count: ? = Firebase.remoteConfig.getLong()
limit: ? = Firebase.remoteConfig.getInt()
json: String? = Firebase.remoteConfig.allToJson()
Messaging
// commonMain
// Read the current default FCM registration token
val token: String = Firebase.messaging.getToken()
// Delete the current default FCM registration token
Firebase.messaging.deleteToken()
Android and iOS also expose topic subscription APIs from their platform source sets. Web exposes foreground onMessage(...), and Desktop uses a local browser bridge for token creation and message delivery.
See the full Messaging module guide for installation, platform setup, target differences, and sample app usage.
Performance
// commonMain
val trace = Firebase.performance.newTrace("checkout_flow")
trace.start()
trace.putAttribute("source", "cart")
trace.incrementMetric("items")
trace.stop()
val metric = Firebase.performance.newHttpMetric("https://example.com/products", "GET")
metric.start()
metric.setHttpResponseCode(200)
metric.setResponsePayloadSize(2048)
metric.stop()
See the full Performance module guide for installation, platform setup, target differences, and sample app usage.
Crashlytics - Experimental
crashlytics exposes Firebase Crashlytics crash reporting APIs through Firebase.crashlytics. This feature is Experimental and currently backed by native SDKs on Android and iOS only.
There is no Firebase Crashlytics SDK for Web (JS/Wasm) or Desktop targets.
// commonMain
Firebase.crashlytics.setCrashlyticsCollectionEnabled(true)
Firebase.crashlytics.setUserId("user-42")
Firebase.crashlytics.setCustomKey("screen", "checkout")
Firebase.crashlytics.log("Checkout started")
Firebase.crashlytics.recordException(throwable)
See the full Crashlytics module guide for installation, platform setup, target differences, and sample app usage.
Platform Setup
Each platform requires a one-time Firebase.initialize() call before accessing Firebase services.
Android
Add the dependency and the Google Services plugin to your app module:
// build.gradle.kts of android target module
plugins {
id("com.google.gms.google-services")
}
Place your google-services.json in the app module of android target, then initialize:
// androidMain
class AppActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Firebase.initialize(this)
}
}
iOS
Add a GoogleService-Info.plist to your app target.
Initialize from Kotlin shared code:
// iosMain
fun FirebaseConfigure() {
Firebase.initialize()
}
Call from Swift:
import shared
final class AppDelegate: NSObject, , {
(
: ,
: [.: ]
) -> {
.()
}
}
Web (JS / Wasm)
Initialize with your full Firebase web config:
// webMain/jsMain/wasmMain
Firebase.initialize(
apiKey = "AAAAAAAAAAAAAAAAAAAAAAAAAAAA-AAAAAAAAAAA",
projectId = "your-project-id",
appId = "1.1111111111:web:AAAAAAAAAAAAAAAAA",
authDomain = "your-project-firebase.firebaseapp.com",
storageBucket = "your-project-firebase.firebasestorage.app",
messagingSenderId = "11111111111111",
measurementId = "A-AAAAAAAAAA",
)
Desktop (JVM)
Initialize before creating the UI:
// desktopMain
Firebase.initialize(
apiKey = "AAAAAAAAAAAAAAAAAAAAAAAAAAAA-AAAAAAAAAAA",
projectId = "your-project-id",
appId = "1.1111111111:web:AAAAAAAAAAAAAAAAA",
authDomain = "your-project-firebase.firebaseapp.com", // optional, defaults from projectId
storageBucket = "your-project-firebase.firebasestorage.app",
messagingSenderId = ,
webVapidKey = ,
measurementProtocolApiSecret = ,
cacheFilePath =
)
The JVM target connects to Firebase via REST APIs using Ktor. Remote Config requires your Firebase project's API key, project ID, and app ID. Analytics uses GA4 Measurement Protocol and also requires a Measurement Protocol API secret from Google Analytics.
The desktop implementation automatically re-fetches config on the specified interval (defaults to 60 minutes). A Firebase Installation ID (FID) is generated and cached locally at cacheFilePath.
Desktop Messaging uses a local loopback browser bridge. See the Messaging module guide for token caching, foreground message handling, and target-specific setup.
License
See LICENSE for details.