Preview and publish your experiment

  • Updated
  • Optimizely Feature Experimentation
  • Optimizely Full Stack (Legacy)
  • Optimizely Web Experimentation
  • Optimizely Performance Edge

Use Preview to ensure that your experiments and campaigns look and work as they should, without force parameters, cookies, or the developer console to check experiment functionality.

Preview slows down the execution of the Optimizely Web Experimentation snippet and does not match the timing of a live experiment.

Use Preview mode to:

  • View draft and published experiments and campaigns.
  • Review multiple live experiments and campaigns that are running on a page.
  • Toggle between variations.
  • Test your site for different audiences.
  • Evaluate the timing of code execution.
  • Confirm that events are firing properly.
  • Go to your site in preview mode without publishing your changes.

Preview persists for 10 minutes after you close it.

If you want to test a live experiment or campaign and share it with many stakeholders, consider setting a test cookie or using the force variation parameter instead. The ?optimizely_token=PUBLIC parameter lets you test draft and paused variations across multiple devices without passing long tokenized URLs between devices.

How Preview works

Preview adds a preview token to your URL: ?optimizely_token=<token>. Optimizely Web Experimentation generates this token to ensure that only users with access to the Optimizely Web Experimentation project can preview draft experiments and campaigns.

The tool uses a combination of query string parameters to display a specific experiment and variation (or campaign and experience).

The Preview token is stored in a cookie that persists for 10 minutes to prevent the token parameter from being lost as you go to the site. While the Preview cookie is stored, instances of your site (including separate tabs and windows) load with Optimizely Web Experimentation Preview mode enabled.

Launch Preview

Launch Preview from the Manage Experiment dashboard. It is active when you have a draft experiment or campaign or your live experiment or campaign has unpublished changes.


To preview a specific variation or experience, go to the variation and click Preview. You enter that variation directly without audience conditions. 


Preview uses the snippet that is already implemented on your website. If that snippet does not match the snippet of the project you are previewing, you must use Optimizely Assistant (the Chrome extension) to inject the desired project's snippet. When that is complete, Preview functions as described in this article.

Click Preview (QA ball) to display a view with tabs: Currently Viewing, Override, and Feed. Drag Preview to drag the module if it covers a part of the page you want to see.


Currently Viewing

The Currently Viewing tab gives you details on the experience you currently see:

  • The experiment or campaign
  • The experience or variation you're bucketed into
  • The audience you are viewing the experience as (when you first open Preview, this is the audience you naturally qualify for)


Toggle Draft Changes to Show or Hide changes that have not been published. Changes not published in your experiment are in yellow. Published changes are in green. 

The Other live experiments you are viewing section lists experiments or campaigns running on the same page for the same audience. Use this prompt to check for conflicts between those experiences. For example, if you target a personalized CTA to luxury travelers on the homepage and test different background images on the same page, ensure these changes look right for a visitor who sees them.


When you first open Preview, the page displays as it would for the audience you naturally qualify for. Use the Override tab to see the page as your other audiences would. The Override tab lets you force specific experiences or variations to display.

  • If multiple experiments are running on a page, toggle between different audiences to see them.
  • If you run an Optimizely Personalization campaign, view the experience you deliver to each audience.


Go to the Currently Viewing tab > Draft Changes > Show to see live and draft changes.

To force a specific variation or experience to display, click Browse for Audiences and choose an audience. Then, select a variation that is available for that audience. Click Apply Changes to preview the page as that audience.

When you view experiments in preview mode, you must set Override Mode to Off to see any other active experiments on the same page.


The Feed tab displays a list of page-level events as they occur. Use this to check the functionality of your experiment or campaign. Click or fire the events you attached to this page to ensure they work correctly.

Events in the feed are triggered through the same code paths as in a live campaign, but no GET request is sent across the network. Any action you take in Preview will not be recorded on your results page.


By default, All events are displayed. You can filter by Campaign, Page, Click events, pageview events, custom events, and Errors.

  • Campaign events  – a campaign is activated on the page for this audience.
  • Page events  – the URL Targeting of a page is activated. For example, you created a page that uses URL targeting to match multiple product detail pages. The page event will fire when a visitor goes to any of those pages. If you created a second page that targets an individual product detail page, that page event fires separately when a visitor sees it. Two separate page events displays in your feed.
  • Click events, pageview events, or custom events  – metrics attached to the experiment or campaign have fired on the page.
  • Errors – errors thrown on the page.
Select the element with a right-click to avoid firing an event when clicking an element. 

Publish your experiment

When everything works the way you want, click Start Experiment to set the experiment live for visitors. See create an experiment for more details.