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Optimizely Knowledge Base

View project or experiment change history

  • View the Change History for your projects
  • Troubleshoot by identifying changes that might have caused problems with your experiments 

Optimizely logs most actions you can perform for a project, like creating a page, modifying a variation, and adding and removing audiences. These actions are listed in the change history, which shows the record of user activity for each of your projects.

If an experiment starts to behave strangely or stops working correctly, you can troubleshoot by checking the change history to see which changes have been made, when, and by which collaborator. The detailed change history creates an activity trail that provides additional security to individuals and teams with multiple collaborators.

In Optimizely X, change history is only available for Web Experimentation, Web Personalization, and Web Recommendations and cannot be accessed in Mobile or Full Stack Projects.

View a project's change history in Optimizely X

Each project’s change history is listed under Experiments > Change History:


If details are available for a change, you’ll see a Show details dropdown menu to the right of the screen. Click the dropdown to view the change details:


Use the dropdown at the top of the page to filter the list according to what was changed. You can filter to show only changes made to audiences, experiments, events, pages, tags, or extensions.


Changes Optimizely saves

Here's a list of the changes Optimizely saves in each project's change history:


Changes saved


  • Created

  • Archived

  • Unarchived

  • Modified name, description, or conditions


  • Created

  • Modified


  • Created

  • Modified


  • Created

  • Archived

  • Unarchived

  • Modified name or description

  • Changed variation:

    • Changed element

    • Inserted HTML or image

    • Added redirect

    • Changed variation CSS or JavaScript

  • Changed shared code (JavaScript or CSS)

  • Added or removed page

  • Added or removed event

  • Changed primary metric

  • Changed traffic allocation

Project JavaScript

All changes

Change detail examples

In general, the change history detail panel displays the original (before changes) in red on the left side and the updated code (after changes) in green on the right side.

Here are some change detail examples to demonstrate the information listed for changes to different features.

Audience Conditions

For each audience condition, you’ll see type and value keys. Check the values for these keys for the specific changes made to the audience.


Change history displays changes to Apply JS, Reset JS, HTML, and CSS in the extension builder.

Variation changes made with the Visual Editor

For changes made to elements using the Visual Editor, a full code representation of the Visual Editor change is visible, so you'll look for the property or attribute that was actually modified. In this example, font-weight was set to "bold."

In the example below, the value for the html key was changed from "Gear for Fall" to "Gear for the cooler months."

Variation changes made with the Code Editor

Change history displays changes to CSS and JavaScript code made with the code editor.