Pages not loading in the editor

  • Updated
  • Optimizely Web Experimentation
  • Optimizely Performance Edge

Are you seeing a message in the Editor: "Sorry, we were unable to load..."? Or having trouble accessing a certain page in the Editor? Maybe you see something that looks like this:

If you are seeing a different problem, keep reading to troubleshoot and resolve issues with page-loading in the Optimizely Experimentation Editor.

The Optimizely Experimentation Desktop App solves many common editor loading issues, including those listed here. Consider installing it if you are having trouble with the web application.

Clear browser cache and cookies

Sometimes the simplest solution when you encounter an editor-loading issue is to clear your browser cache and cookies.

Google Chrome

  1. Type chrome://settings/clearBrowserData in the browser bar (where you usually enter a URL).
  2. From the dropdown menu, select a time range to clear your entire cache/cookies.

    Then, check:

    • Browsing history
    • Download history
    • Cookies and other site and plug-in data
    • Cached images and files

  3. Click Clear browsing data.
  4. Close all your Chrome windows and re-open Chrome.


  1. In the browser navigation menu, select History > Clear Recent History.
  2. From the drop-down menu select a desired time range or Everything to clear your history.

    In the Details panel, select:

    • Browsing & Download History
    • Cookies
    • Cache
  3. Click Clear now.
  4. Close all of your Firefox windows and re-open Firefox.

Internet Explorer

Optimizely Experimentation only supports IE8 and higher.

  1. Select Tools > Delete Browsing History (in older versions) or Safety > Delete Browsing History (in newer versions) from the browser's top-navigation menu or settings menu.
  2. Deselect Preserve Favorites website data.


    • Temporary Internet files and website files
    • Cookies and website data
    • History
  3. Click Delete.
  4. Close the IE windows and re-open IE.


For Desktop

  1. Select Safari > Clear History from the browser's top-navigation menu.
  2. From the Clear menu, select your desired time range or all history to clear your browser cache and cookies.
  3. Click Clear History, then close all of your Safari windows and re-open Safari.

For iOS

  1. Open the Settings app.
  2. Tap Safari.
  3. Tap Clear History and Website Data, then close all of your Safari windows and re-open Safari.

For Android

  1. From the Settings menu, tap Apps or Application Manager.
  2. Choose the All tab.
  3. Find your web browser, then tap it.
  4. Tap Clear Data, then Clear Cache, then close all of your browser windows and re-open your browser.

Android encompasses a wide variety of devices and browsers, so these steps may differ for you.

Common editor page-loading issues

Try these steps, one by one, to try to resolve some common page-loading issues.

  1. Confirm that your page loads consistently outside of Optimizely Experimentation. Make sure you can reach the page in your browser, outside of Optimizely Experimentation, multiple times in a row. If the page does not load outside of Optimizely Experimentation, it may not load in Optimizely Experimentation either.
  2. Clear your browser cache and cookies. Then, reload the page.
  3. Confirm that the Optimizely Experimentation snippet is installed: open the developer console and type optimizely. If the search returns an error, such as "optimizely is undefined," the snippet is not implemented correctly.

    See Implement the one-line snippet for Optimizely Web Experimentation. Make sure the snippet is installed synchronously at the top of your <head> tag.

  4. Try loading the page via the pop-out editor. See Visual Editor in Optimizely Web Experimentation and Optimizely Performance Edge.

Less common editor page-loading issues

  1. Check the JS console for errors that do not normally exist on the page. Filter the console output for error logs.
    • If you see an error within bundle or client.js/[projectID].js, there may be a conflict.
    • If your site is using Content Security Policies, the error will begin with: refused to execute inline script because it violates the the following Content Security Policy. In some scenarios, you can use a browser extension to get around this issue.
  2. Confirm whether your site is configured to disallow parameters it does not expect and parameters that include raw URLs. To check this, try to load the page with an innocuous query parameter like ?test=true and then a parameter that contains a raw URL. If your site disallows unexpected parameters, you need to allow-list Optimizely Experimentation's Editor parameters. Contact support to learn more or try the Optimizely Experimentation Desktop App.
  3. Check whether the page loads outside the Editor within an arbitrary iframe.

    Some sites have frame-busting logic that prevents them from being iframed correctly. Try constructing an iframe on any page through the browser console to see if the page loads correctly. For example:

    <iframe src='' style='width:800px;height:600px'></iframe>

    If the page will not load in an arbitrary iframe, you may need to whitelist the Optimizely Experimentation domain ( as a valid host. Or, try the Optimizely Experimentation Desktop App.

If you tried the steps in this article, but still cannot correctly load your page in the Editor, try the Optimizely Assistant Chrome extension.