---
title: Javascript-SDK - 6.4.0
slug: feature-experimentation/release-notes/javascript-sdk-6-4-0
docTags: 
createdAt: 2026-07-20T15:45:22.682Z
---

## \[6.4.0] - May 7, 2026

### New Features

**Feature Rollout**: Added support for Feature Rollouts, a new experiment type combining Targeted Delivery simplicity with A/B test measurement capabilities. Feature Rollouts enable progressive rollouts with full impact analytics, metric tracking, and confidence intervals. See [Feature Rollout docs](docId\:FYbuu0asBt5htNNrEp235) for more information.

- Add Feature Rollout support ([#1140](https://github.com/optimizely/javascript-sdk/pull/1140))

### Bug Fixes

- Export `UserProfileServiceAsync` type

[https://github.com/optimizely/javascript-sdk/releases/tag/v6.4.0](https://github.com/optimizely/javascript-sdk/releases/tag/v6.4.0)