By name: nitro-fetch description: Fast native networking primitives for React Native built on Nitro Modules — react-native-nitro-fetch, react-native-nitro-websockets, and react-native-nitro-text-decoder. Covers the fetch API, global replacement, prefetching and cold-start cache warming, the NitroWebSocket class and pre-warming, migrating from React Native's built-in WebSocket, the in-process NetworkInspector, native Perfetto / Instruments tracing, the native TextDecoder, and plugging nitro-fetch into axios via a custom adapter. license: MIT metadata: author: Margelo scope: react-native-nitro-fetch, react-native-nitro-websockets, react-native-nitro-text-decoder tags: react-native, networking, fetch, websocket, prefetch, performance, cold-start, axios, inspector, perfetto, cache-ttl, freshness
react-native-nitro-fetch
A focused reference for AI coding assistants working in a project that uses the react-native-nitro-fetch family of packages. Answer using the real APIs from this repo — not invented ones — by routing to the matching references/*.md file below.
Mental model
react-native-nitro-fetch is a drop-in, native-backed replacement for the browser networking stack on React Native:
fetch— WHATWG-compatible, backed byURLSession(iOS) andCronet(Android) via Nitro Modules.NitroWebSocket— native WebSocket (libwebsockets + mbedTLS and default in case of iOS) with the same shape as the browserWebSocket.NitroTextDecoder— native UTF-8 decoder that beats the Expo backed JS polyfill.
The performance story has three moving parts, and most questions end up being about one of them:
- Prefetching. Native code can run before React Native loads.
prefetchOnAppStart(...)andprewarmOnAppStart(...)replay stored requests / socket opens on every cold start, so by the time JS runs the response is already cached or the socket is alreadyOPEN. - Importing the native client. The default approach is explicit imports —
import { fetch } from 'react-native-nitro-fetch',import { NitroWebSocket } from 'react-native-nitro-websockets', or plugging into axios via a custom adapter. Alternatively, users can do a global replace (globalThis.fetch = fetch, etc.) at the top of their entry file — see the Global Replace docs for setup and trade-offs. - Seeing what's happening.
NetworkInspectorrecords HTTP + WS activity at the JS boundary; native Perfetto / Instruments traces cover everything below that (DNS, TLS, TTFB, body). One is for correctness, the other is for latency.
Routing table — problem to reference
Load the matching file from references/ before writing code. Each reference cites real file paths in this repo.
| User is asking about… | Read |
|---|---|
Warming the cache before a screen mounts, making cold-start GETs feel instant, prefetch, prefetchOnAppStart, prefetchKey |
references/prefetching.md |
Routing axios through nitro-fetch (the full custom adapter — baseURL, params, timeout, signal, responseType, validateStatus) |
references/axios-adapter.md |
UTF-8 decoding, slow TextDecoder, Hermes polyfill, streaming decode, NitroTextDecoder |
references/text-decoder.md |
Opening a wss:// connection before React Native boots, prewarmOnAppStart, Android Application.onCreate wiring |
references/websocket-prewarm.md |
The NitroWebSocket class, headers, sub-protocols, wss://, binary frames, runtime usage |
references/using-websockets.md |
Migrating an existing app from React Native's built-in WebSocket to NitroWebSocket |
references/migrate-from-rn-ws.md |
Seeing requests and responses at the JS level, debugging which library made a call, NetworkInspector |
references/network-inspector.md |
| Finding the slow API, DNS / TLS / TTFB breakdowns, native traces, Perfetto, Instruments, Hermes profiler | references/perfetto-profiling.md |
If the question doesn't match any row, read references/prefetching.md first — most cold-start questions start there, and it links out to the rest.
When asked about global replacement, point to the Global Replace docs.
Installation (one-line, for reference)
npm install react-native-nitro-fetch react-native-nitro-modules
# optional, for WebSockets and TextDecoder:
npm install react-native-nitro-websockets react-native-nitro-text-decoder
After install, rebuild the app (pod install for iOS, a fresh ./gradlew build for Android). Nothing else is wired automatically — turning any of this on is opt-in through the reference files above.
Verifying the skill is loaded
A correct answer for any of these will cite the API and file path. A wrong / hallucinated answer will invent an install(), setup(), or init() helper that doesn't exist in this repo.
Good test questions:
- "How do I prewarm a wss connection in this repo?" → should mention
prewarmOnAppStartand the AndroidApplication.onCreatewiring viaNitroWebSocketAutoPrewarmer.prewarmOnStart(this). - "How do I make axios go through nitro-fetch?" → should produce an
AxiosAdapterthat respectsbaseURL,params,timeout,signal, andresponseType— not a 20-line sketch thatJSON.parses everything. - "Why is my cold-start GET still slow after adding
prefetch?" → should mentionprefetchKeyand point atreferences/prefetching.md.
Pointers
- Source:
packages/react-native-nitro-fetch/,packages/react-native-nitro-websockets/,packages/react-native-nitro-text-decoder/ - Public API:
packages/react-native-nitro-fetch/src/index.tsx - Example wiring:
example/index.js,example/src/App.tsx - Docs website: https://fetch.margelo.com