Release 4.3.0

4.3.0

May 14, 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 for more information.

• Add Feature Rollout support (#400)
• Remove experiment type validation from config parsing (#402)
• Documentation improvement (#399)
• Event retry adjustment (#398)

Release 4.2.0

4.2.0

Nov 13, 2025

New Features

Contextual Multi-Armed Bandit (CMAB)

• Add support for CMAB experiments with new configuration options and cache control (#390, #391, #392, #393, #394).
• To get decision from CMAB rules, decide and related methods must be used.
• For configuration details, see the CMAB configuration documentation.

Holdouts

• Add Holdouts Feature Experimentation feature (#384, #386, #387).

Release 4.1.0

4.1.0

November 7th, 2024

Enhancement

• Added support for batch processing in DecideAll and DecideForKeys, enabling more efficient handling of multiple decisions in the User Profile Service. (#375)

Bug Fixes

• GitHub Actions YAML files vulnerable to script injections (#372)

Release 4.0.0

4.0.0

January 16th, 2024

New Features

Advanced Audience Targeting

The 4.0.0 release introduces a new primary feature, Advanced Audience Targeting enabled through integration with Optimizely Data Platform (ODP) ( #305, #310, #311, #315, #321, #322, #323, #324).

You can use ODP, a high-performance Customer Data Platform (CDP), to easily create complex
real-time segments (RTS) using first-party and 50+ third-party data sources out of the box. You can create custom schemas that support the user attributes important
for your business, and stitch together user behavior done on different devices to better understand and target your customers for personalized user experiences. ODP can
be used as a single source of truth for these segments in any Optimizely or 3rd party tool.

With ODP accounts integrated into Optimizely projects, you can build audiences using segments pre-defined in ODP. The SDK will fetch the segments for given users and
make decisions using the segments. For access to ODP audience targeting in your Feature Experimentation account, please contact your Optimizely Customer Success Manager.

This version includes the following changes:

• New API added to OptimizelyUserContext:
  • FetchQualifiedSegments(): this API will retrieve user segments from the ODP server. The fetched segments will be used for audience evaluation. The fetched data will be stored in the local cache to avoid repeated network delays.
  • When an OptimizelyUserContext is created, the SDK will automatically send an identify request to the ODP server to facilitate observing user activities.
• New APIs added to OptimizelyClient:
  • SendOdpEvent(): customers can build/send arbitrary ODP events that will bind user identifiers and data to user profiles in ODP.

For details, refer to our documentation pages:

• Advanced Audience Targeting
• Server SDK Support
• Initialize C# SDK
• OptimizelyUserContext C# SDK
• Advanced Audience Targeting segment qualification methods
• Send Optimizely Data Platform data using Advanced Audience Targeting

Polling warning

Add warning to polling intervals below 30 seconds (#365)

Breaking Changes

• OdpManager in the SDK is enabled by default. Unless an ODP account is integrated into the Optimizely projects, most OdpManager functions will be ignored. If needed, OdpManager can be disabled when OptimizelyClient is instantiated.
• ProjectConfigManager interface additions + implementing class updates
• Evaluate() updates in BaseCondition

Bug Fixes

• Return Latest Experiment When Duplicate Keys in Config enhancement

Documentation

• Corrections to markdown files in docs directory (#368)
• GitHub template updates (#366)

Release 3.11.4

3.11.4

July 26, 2023

Bug Fix

• Fix Last-Modified date & time format for If-Modified-Since (#361).

Release 3.11.3

3.11.3

July 18, 2023

Bug Fix

• Last-Modified in header not found and used to reduce polling payload (#355).

Release 4.0.0-beta

April 28th, 2023

New Features

The 4.0.0-beta release introduces a new primary feature, Advanced Audience Targeting
enabled through integration with Optimizely Data Platform (ODP) (#305,#310,#311,#315,#321,#322,#323,#324).

You can use ODP, a high-performance Customer Data Platform (CDP), to easily create complex
real-time segments (RTS) using first-party and 50+ third-party data sources out of the box. You can create custom schemas that support the user attributes important
for your business, and stitch together user behavior done on different devices to better understand and target your customers for personalized user experiences. ODP can
be used as a single source of truth for these segments in any Optimizely or 3rd party tool.

With ODP accounts integrated into Optimizely projects, you can build audiences using segments pre-defined in ODP. The SDK will fetch the segments for given users and
make decisions using the segments. For access to ODP audience targeting in your Feature Experimentation account, please contact your Optimizely Customer Success Manager.

This version includes the following changes:

• New API added to OptimizelyUserContext:
  • FetchQualifiedSegments(): this API will retrieve user segments from the ODP server. The fetched segments will be used for audience evaluation. The fetched data will be stored in the local cache to avoid repeated network delays.
  • When an OptimizelyUserContext is created, the SDK will automatically send an identify request to the ODP server to facilitate observing user activities.
• New APIs added to OptimizelyClient:
  • SendOdpEvent(): customers can build/send arbitrary ODP events that will bind user identifiers and data to user profiles in ODP.

For details, refer to our documentation pages:

• Advanced Audience Targeting
• Server SDK Support
• Initialize C# SDK
• OptimizelyUserContext C# SDK
• Advanced Audience Targeting segment qualification methods
• Send Optimizely Data Platform data using Advanced Audience Targeting

Breaking Changes

• OdpManager in the SDK is enabled by default. Unless an ODP account is integrated into the Optimizely projects, most OdpManager functions will be ignored. If needed, OdpManager can be disabled when OptimizelyClient is instantiated.
• ProjectConfigManager interface additions + implementing class updates
• Evaluate() updates in BaseCondition

3.11.2

March 15th, 2023

• Update README.md and other non-functional code to reflect that this SDK supports both Optimizely Feature Experimentation and Optimizely Full Stack. (#331, #332).

Bug Fixes

• Fix for incorrect documentation on Optimizely.IsFeatureEnabled (#304)

Release 3.11.2.1

March 24, 2023

NuGet requires a semantic version increase to "republish".

Bug Fix

• Corrections to nuspec generated during signing and upload.

Release 3.11.2

March 16th, 2023

• Update README.md and other non-functional code to reflect that this SDK supports both Optimizely Feature Experimentation and Optimizely Full Stack. (#331, #332).
• Changes to GitHub Actions jobs (#335)
• Some edits .editorconfig (more complete linting rules coming) (#335)

Bug Fixes

• Fix for incorrect documentation on Optimizely.IsFeatureEnabled (#329)
• Update version of Newtonsoft.Json & NJsonSchema (#330) to address Issue #328

Release 3.11.1

July 27th, 2022

Bug Fixes

• Handle possible empty string rolloutId in datafile (#304)