EOL Announcement for Preview3 CMS REST API
Action Required: Migrate Preview3 API Integrations to CMS REST API v1 Before August 1, 2026
If your SaaS CMS applications are currently using the Preview3 CMS REST API endpoints, please plan to migrate to CMS REST API v1 before August 1, 2026.
On August 1, 2026, we will retire the Preview3 endpoints and begin disabling access. Applications that continue to rely on Preview3 after this date may experience failed requests and service interruptions.
Who Is Affected?
You are affected by this change if your SaaS CMS integrations are currently making requests to Preview3 endpoints (typically URLs containing /preview3/).
If your applications are already using CMS REST API v1, no action is required.
We recognize that API migrations require planning and effort, and we appreciate the work our customers invest in keeping their integrations current. To help ensure a smooth transition, we've provided a migration guide (see below) and have maintained support for both versions since the release of v1 in May. This announcement is the first to underscore the importance of staying current and making the change to CMS REST API v1 to avoid disruption.
What Is Changing?
With the general availability of CMS REST API v1 on May 5, 2026, the Preview3 APIs entered a deprecation phase and are now approaching end-of-life.
Key points to know:
- Preview3 support ends August 1, 2026.
- Preview3 was released as an experimental API and was not recommended for production workloads.
- CMS REST API v1 provides the same core capabilities through stabilized, production-ready endpoints.
- Mixing Preview3 and v1 endpoints is supported until the August 1, 2026 retirement date.
- No new fixes, enhancements, or support updates are being made to Preview3. All ongoing investment is focused on v1 and future releases.
Will There Be Breaking Changes?
Yes. Some breaking changes were introduced as part of the transition from Preview3 to v1.
Before migrating, please review the migration documentation:
These resources provide detailed guidance on the changes and recommended migration approach.
Why Are We Retiring Preview3?
Maintaining multiple API versions increases complexity for both customers and Optimizely. As v1 has been generally available for several months and provides a stable, supported alternative, retiring Preview3 allows us to focus on delivering higher reliability, better performance, and faster innovation across the platform.
How Can I Stay Informed?
We recommend subscribing to the following channels for future API lifecycle and platform updates:
- CMS Release Notes (support.optimizely.com)
- Optimizely Slack Community
- Optimizely Developer Blog Community (World.optimizely.com)
These channels are typically the first places where deprecations, support timelines, and migration guidance are communicated.
For additional information about API lifecycle and support policies, please refer to the CMS API documentation.
Thank You
Thank you for your partnership and for helping us continue to improve the CMS developer experience. If you have questions about your migration strategy or encounter challenges during the transition, please reach out to our team—we're here to help.
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