Hermes V1, New Architecture, and the New Performance Baseline

Hermes V1, New Architecture, and the New Performance Baseline

React Native performance in 2026 is less about one tuning trick and more about a new baseline. The framework has moved into a New Architecture-only era, Hermes V1 is now the default JavaScript engine, and major libraries are starting to assume that foundation.

That does not make performance automatic. Teams still need profiling, measurement, and careful screen work. The difference is that the default stack now removes more old compatibility paths before the app team begins tuning.

The New Baseline

React Native 0.82 makes the New Architecture the only architecture The React Conf keynote framed the shift directly: the Legacy Architecture was already frozen and no longer used at Meta, then React Native 0.82 made the New Architecture the only runtime path. That is the real starting point for the current performance story.

Legacy classes start leaving the codebase React Native 0.84 continued removing Legacy Architecture code from iOS and Android. That work matters because a platform cannot keep improving its runtime while treating old and new architecture paths as equal forever.

Reanimated 4 is built for the New Architecture Reanimated 4 shows how library assumptions are changing. Its docs tie the 4.x line to the New Architecture, and the keynote describes it as a rewrite built for that world. Libraries can now aim at the modern stack instead of carrying every old path.

Hermes V1 Becomes The Default Engine

Hermes V1 is announced as the next runtime step React Native 0.84 made Hermes V1 the default JavaScript engine on iOS and Android. That means many apps get the new runtime baseline without adding special configuration.

Hermes V1 improves the VM and compiler The important point is not that every app becomes fast just by upgrading. The engine is doing more work in the default path, so teams begin from a stronger compiler and virtual machine before they write app-specific optimizations.

Modern JavaScript support reduces compatibility overhead Native support for more modern JavaScript features can reduce the amount of Babel and polyfill work needed before code runs on-device. Cleaner runtime support makes performance easier to reason about and gives profiling tools a less distorted picture.

Measurement Still Decides

The modern stack gives teams better defaults: New Architecture-only React Native, Hermes V1, Reanimated 4 on the new foundation, Web Performance APIs, DevTools Performance tracing, and a stronger animation backend. Those pieces help, but they do not replace measurement.

App performance still depends on data fetching, navigation structure, expensive renders, image loading, native module behavior, animation choices, and the way users move through screens. The new baseline makes the work cleaner. It does not make product-specific performance work disappear.

Summary

Hermes V1 and the New Architecture are not separate release-note items. Together, they mark a cleaner React Native performance baseline. The old architecture is no longer the active path, Hermes V1 moves more runtime work into the default engine, and libraries such as Reanimated can build directly on the modern foundation. Teams still need to measure, but they are measuring on a better stack.