---
title: React-SDK - 4.2.1
slug: feature-experimentation/release-notes/react-sdk-4-2-1
docTags: 
createdAt: 2026-10-04T12:21:30.000Z
---

## \[4.2.1] - September 18, 2026

### Bug Fixes

- Use an updated datafile cache key so the SDK no longer reads a stale or malformed datafile persisted by an older SDK version.

[https://github.com/optimizely/react-sdk/releases/tag/4.2.1](https://github.com/optimizely/react-sdk/releases/tag/4.2.1)