kmp-user-agent

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Android Usage ​

site.lempert:user-agent is the Android build of kmp-user-agent, published to Maven Central straight from the library's own Kotlin/Android target -- the same detection/generation logic used by every other platform.

Install ​

Add the dependency to your module's build.gradle.kts (Maven Central is already in most projects' default repositories):

kotlin
dependencies {
    implementation("site.lempert:user-agent:0.2.0")
}

The 0.2.0 above is a hand-pinned version, not something Gradle resolves for you -- bump it whenever you upgrade to a newer release, checking the Maven Central listing for the latest published version.

No manifest changes or runtime permissions are required -- parsing and generating are pure string logic. The library targets minSdk = 24 and above, so it works on any Android version your app already supports if your own minSdk is 24 or higher. If your app's minSdk is lower than 24, AGP will fail the build with an error like uses-sdk:minSdkVersion N cannot be smaller than version 24 declared in library; the fix is to raise your app's minSdk to 24.

Parse ​

Kotlin's vararg support means you call UserAgentParser/UserAgentGenerator directly with the packs you want -- no .get() or array-wrapping, unlike the JS bindings.

A real UA string to parse is available without any permission via System.getProperty("http.agent"), which returns the device's default User-Agent. This property can return null in some environments (unit tests, some non-standard JVMs), so the ?: "" fallback below is a deliberate guard, not an arbitrary default:

kotlin
import site.lempert.useragent.UserAgentAllTypes
import site.lempert.useragent.UserAgentParser

val userAgent = System.getProperty("http.agent") ?: ""

val info = UserAgentParser(UserAgentAllTypes)(userAgent)

println(info.browser) // e.g. Component(name=Chrome, version=128.0)
println(info.engine)
println(info.os)
println(info.device)
println(info.bot)
println(info.aiAgent)

The function returned by UserAgentParser(...) (and likewise UserAgentGenerator(...)) is cheap to construct, but it's still worth building once and reusing it across calls rather than rebuilding it every time -- the same way the repo's own androidApp sample caches it with Compose's remember { }. See Core Concepts' "Cost of calling the factories" for details.

Generate ​

kotlin
import site.lempert.useragent.Component
import site.lempert.useragent.UserAgentAllTypes
import site.lempert.useragent.UserAgentGenerator
import site.lempert.useragent.UserAgentInfo

val userAgentString = UserAgentGenerator(UserAgentAllTypes)(
    UserAgentInfo(
        browser = Component("Chrome", "128.0"),
        engine = Component("Blink", "128.0"),
        os = Component("Android", "14"),
        device = null,
    ),
)

println(userAgentString)

Next steps ​

For the platform-agnostic UserAgentInfo model and the built-in type packs behind UserAgentAllTypes used above, see Core Concepts -- and the Type Reference for every name each pack recognizes.