Other packages

The packages not big enough for their own page, plus the internal-only ones.

Renderers

react-native-renderer

Path: packages/react-native-renderer/. The Fabric host config (the legacy "Paper" renderer was removed in early 2026 via #36285). Bridges to React Native's C++ shadow tree via the JS-to-Native bridge. Key files:

• packages/react-native-renderer/src/ReactFiberConfigFabric.js — the host config (~27,000 chars).
• packages/react-native-renderer/src/ReactFabric.js — the public mount API (render, unmountComponentAtNode, …).
• packages/react-native-renderer/src/ReactFabricEventEmitter.js — Fabric event dispatch.
• packages/react-native-renderer/src/ReactFiberConfigFabricWithViewTransition.js — view-transition extensions for Fabric.
• packages/react-native-renderer/src/ReactNativeFeatureFlags.js — RN-specific flag overrides.

react-art

Path: packages/react-art/. Renderer for the ART shape library, a thin abstraction over Canvas / SVG / VML. ~five files of host-config plus a tiny public API. Mostly used by very old React Native projects; kept primarily for backwards compatibility.

react-test-renderer

Path: packages/react-test-renderer/. Renders to a JSON tree. Used by snapshot testing libraries that don't want to bring up a DOM environment. Slowly being deprecated in favor of @testing-library/react for end-user testing — but the package itself is still maintained and shipped.

react-noop-renderer

Path: packages/react-noop-renderer/. In-memory renderer; host instances are plain JS objects appended to arrays. The React team's preferred test platform for reconciler features — every reconciler bug fix usually adds a regression test against react-noop-renderer.

Server / streaming

react-client

Path: packages/react-client/. Shared client runtime for every Flight client. Parses incoming Flight stream rows, allocates Promise-backed chunk records, materializes React elements, and resolves client / server references. The bulk is packages/react-client/src/ReactFlightClient.js (~3,000 lines).

react-flight-server-fb

Path: packages/react-flight-server-fb/. Facebook-internal Flight server, separated from the shared react-server so that the FB bundler can ship a smaller surface. Added in #36309 (Apr 2026).

react-markup

Path: packages/react-markup/. Renders an RSC tree to a string of markup, intended for static contexts that can't stream (e.g. emails, edge functions with response-size limits). Built on top of Fizz with all suspense support stripped.

Hooks-adjacent

use-sync-external-store

Path: packages/use-sync-external-store/. The shimmed-on-old-React version of useSyncExternalStore. Lets libraries (Redux, Zustand) target React 16/17 + 18+ uniformly without giving up the new hook.

use-subscription

Path: packages/use-subscription/. Older subscribe-to-external-source API. Now an alias for useSyncExternalStore. Kept for backward compatibility.

react-cache

Path: packages/react-cache/. The original (pre-React 18) experimental data-cache primitive. Mostly superseded by Suspense + the cache() API from react/cache. Still in the tree, mostly unmodified.

react-suspense-test-utils

Path: packages/react-suspense-test-utils/. Helpers for asserting Suspense behavior (createResource and friends) in tests.

Reflection / inspection

react-is

Path: packages/react-is/. Tiny — isValidElement, typeOf(element) returning the symbol kind. Used by libraries that want to detect React elements without depending on the entire react package.

react-debug-tools

Path: packages/react-debug-tools/. Low-level fiber inspection: re-runs a function component with a fake dispatcher to label hook cells. Used by DevTools and act warnings. Public API but not advertised.

Refresh / hot reloading

react-refresh

Path: packages/react-refresh/. The fast-refresh runtime injected by bundler plugins (Vite, Next.js, Metro, ...). Provides register, signature, performReactRefresh, etc. Co-evolves with the matching Babel plugin (which lives in the bundler ecosystem, not here).

Test infrastructure (internal-only)

internal-test-utils

Path: packages/internal-test-utils/. Not published. Provides waitForAll, waitForPaint, waitFor, assertLog, and other helpers used by every reconciler test in the repo.

dom-event-testing-library

Path: packages/dom-event-testing-library/. Internal-only. Synthesizes DOM events with the right behavior for React's synthetic event system — what react-dom's tests use.

jest-react

Path: packages/jest-react/. Jest matchers for React renderer output (toFlushAndYield, toMatchRenderedOutput, ...). Published, but its main user is this repo.

Shared / internal

shared

Path: packages/shared/. Not published — bundled into each consuming package. Holds:

• packages/shared/ReactSymbols.js — the table of REACT_*_TYPE symbols.
• packages/shared/ReactFeatureFlags.js — the canonical feature-flag list.
• packages/shared/forks/ReactFeatureFlags.<channel>.js — per-channel overrides (www, www-modern, test-renderer, native-fb, native-oss).
• packages/shared/ReactSharedInternals.js — re-export bridge for the dispatcher / current owner.
• packages/shared/ReactErrorUtils.js, ReactComponentStackFrame.js, getComponentNameFromType.js, consoleWithStackDev.js, etc.

packages/shared/ReactVersion.js contains the version string — generated from ReactVersions.js at the repo root by the build pipeline.