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Why React Native Ships Its Own JavaScript Engine
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If you build apps with React Native, you have probably heard the word Hermes. Hermes is the engine that runs your JavaScript code inside your app. Starting with React Native version 0.69, something changed in how Hermes is given to you, and this change is called ‘Bundled Hermes.’
In simple words, it means React Native now comes packaged together with its own matching version of Hermes, every single time. You do not need to guess which version of Hermes works with which version of React Native anymore. They come as one pair, built and tested together.
Let’s break down what this really means, why it happened, and how it affects your day-to-day work as a developer.
What Is Hermes, Really?
Hermes is a JavaScript engine. Think of it as the part of your app that reads your JavaScript code and turns it into actions your phone can actually understand. Every React Native app needs an engine like this to run.
For a long time, Hermes and React Native were built and released separately, almost like two different products made by two different teams. You had a version of React Native, and you had a separate version of Hermes, and it was up to you to figure out if they actually worked well…
