Release 6.2.0

[6.2.0] - October 23, 2025

New Features

• Added support for Contextual Multi-Armed Bandit (CMAB): Added support for CMAB experiments(Contextual Bandits rules) with new configuration options and cache control. To get decision from CMAB rules, decideAsync and related methods must be used. The sync decide method does not support CMABs and will just skip CMAB rules while making decision for a flag.

  CMAB Configuration Options

  The following new options have been added to configure the cmab cache:

  import { createInstance } from '@optimizely/optimizely-sdk'
  
  const optimizely = createInstance({
    // ... other config options
    cmab: {
      cacheSize: 1000,      // Optional: Set CMAB cache size (default: 1000)
      cacheTtl: 30 * 60 * 1000,     // Optional: Set CMAB cache TTL in milliseconds (default: 30 * 60 * 1000)
      cache: customCache    // Optional: Custom cache implementation, instance of CacheWithRemove interface
    }
  });

  CMAB-Related OptimizelyDecideOptions

  New decide options are available to control CMAB caching behavior:

  • OptimizelyDecideOption.IGNORE_CMAB_CACHE: Bypass CMAB cache for fresh decisions
  • OptimizelyDecideOption.RESET_CMAB_CACHE: Clear and reset CMAB cache before making decisions
  • OptimizelyDecideOption.INVALIDATE_USER_CMAB_CACHE: Invalidate CMAB cache for the particular user and experiment

  // Example usage with CMAB decide options
  const decision = await userContext.decideAsync('feature-flag-key', [
    optimizelySdk.enums.OptimizelyDecideOption.IGNORE_CMAB_CACHE
  ]);

Bug Fixes

• Flush events without closing client on page unload which causes event processing to stop working when page is loaded from bfcache (#1087)
• Fixed typo in clientEngine option (#1095)

Release 5.4.0

[5.4.0] - Oct 13, 2025

New Features

• Added customHeaders option to datafileOptions for passing custom HTTP headers in datafile requests (#1092)

Bug Fixes

• Fix the EventTags type to allow event properties (#1040)
• Fix typo in event.experimentIds field in project config (#1088)

Release 6.1.0

[6.1.0] - September 8, 2025

New Features

• Added multi-region support for logx events (#1072)

Performance Improvements

• Improved performance of variations parsing from datafile (#1080)
• General cleanups and improvements in event processing (#1073)

Release 6.0.0

[6.0.0] - May 29, 2025

Breaking Changes

• Modularized SDK architecture: The monolithic createInstance call has been split into multiple factory functions for greater flexibility and control.
• Core functionalities (project configuration, event processing, ODP, VUID, logging, and error handling) are now configured through dedicated components created via factory functions, giving you greater flexibility and control in enabling/disabling certain components and allowing optimizing the bundle size for frontend projects.
• onReady Promise behavior changed: It now resolves only when the SDK is ready and rejects on initialization errors.
• event processing is disabled by default and must be explicitly enabled by passing a eventProcessor to the client.
• Event dispatcher interface updated to use Promises instead of callbacks.
• Logging is disabled by default and must be explicitly enabled using a logger created via a factory function.
• VUID tracking is disabled by default and must be explicitly enabled by passing a vuidManager to the client instance.
• ODP functionality is no longer enabled by default. You must explicitly pass an odpManager to enable it.
• Dropped support for older browser versions and Node.js versions earlier than 18.0.0.

New Features

• Added support for async user profile service and async decide methods (see dcoumentation for User Profile Service and Decide methods)

Migration Guide

For detailed migration instructions, refer to the Migration Guide.

Documentation

For more details, see the official documentation: JavaScript SDK.

Release 5.3.5

[5.3.5] - Jan 29, 2025

Bug Fixes

• Rollout experiment key exclusion from activate method(#949)
• Using optimizely.readyPromise instead of optimizely.onReady to avoid setTimeout call in edge environments. (#995)

Release 4.10.1

[4.10.1] - November 18, 2024

Changed

• update uuid module improt and usage (#961)

Release 5.3.4

[5.3.4] - Jun 28, 2024

Changed

• crypto and text encoder polyfill addition for React native (#936)

Release 5.3.3

[5.3.3] - June 06, 2024

Changed

• queueMicroTask fallback addition for embedded environments / unsupported platforms (#933)

Release 5.3.2

[5.3.2] - May 20, 2024

Changed

• Added public facing API for ODP integration information (#930)

Release 5.3.1

[5.3.1] - May 20, 2024

Changed

• Fix Memory Leak: Closed http request after getting response to release memory immediately (node) (#927)