React Native 0.84 making Hermes V1 the default is a baseline shift. Performance improvements matter most when they arrive without every team needing a custom runtime strategy. Defaults are where platform maturity shows up.
The release also continues the removal of Legacy Architecture pieces and ships precompiled iOS binaries by default. Together, those changes reduce the amount of infrastructure work teams carry just to get to a modern React Native setup.
The upgrade still deserves care. JavaScript engine changes can expose timing assumptions, serialization edges, and native module behavior that older builds tolerated. Precompiled binaries can also change how local patches or unusual build setups behave.
The practical test plan:
- Measure startup and key interactions before and after the upgrade.
- Run crash reporting comparisons on a staged rollout.
- Verify native modules that cross the JS boundary heavily.
- Check iOS CI build times and cache behavior.
The strategic read is positive. React Native is moving toward stronger defaults, and that lets product teams spend less effort maintaining platform plumbing.
Official source: React Native 0.84 - Hermes V1 by Default.