Cronet on Android

Android uses Google's embedded Cronet through the Java CronetEngine API, called from Kotlin. There is no custom C/JNI Cronet wrapper — the library talks to Cronet via org.chromium.net.*.

Dependency

org.chromium.net:cronet-embedded is declared in packages/react-native-nitro-fetch/android/build.gradle:

api "org.chromium.net:cronet-embedded:${cronetVersion}"

cronetVersion defaults to 141.7340.3 and can be overridden with a NitroFetch_cronetVersion gradle property. The embedded variant bundles the native Chromium net stack, so no Play Services dependency is required.

Engine

A single CronetEngine is created lazily and shared for the process lifetime (NitroFetch.kt, getEngine()):

• Logs every available CronetProvider and prefers the one whose name contains "Native" (avoids Play-Services DNS quirks); falls back to the default provider.
• Built with enableHttp2(true), enableQuic(true) (HTTP/3), and enableBrotli(true).
• Disk cache: HTTP_CACHE_DISK, 50 MB, at <cacheDir>/nitrofetch_cronet_cache.
• User-Agent: NitroFetch/1.0.
• Callbacks run on a fixed-size NitroCronet-io thread pool.

NitroFetch.shutdown() tears the engine down (best-effort).

Request paths

• Buffered (NitroFetchClient.kt): request() (async Promise) and requestSync() (used by worklets) build a UrlRequest, accumulate the body, and resolve a NitroResponse. Cancellation is wired through cancelRequest(requestId).
• Streaming (NitroCronet.kt): newUrlRequestBuilder(url) exposes a UrlRequestBuilder whose onResponseStarted / onReadCompleted callbacks drive a ReadableStream (used by fetch(url, { stream: true })).
• Prefetch / auto-prefetch (AutoPrefetcher.kt, NitroFetchClient.kt): results are kept in FetchCache and served with a nitroPrefetched: true header.