relevant products:
  • Optimizely X Web Experimentation
  • Optimizely X Web Personalization
  • Optimizely X Web Recommendations
  • Optimizely Classic

This article will help you:
  • Figure out why a page isn't loading in the Editor 
  • Diagnose and fix common editor-loading issues
  • Clear your browser cache and cookies

Are you seeing a message in the Editor: "Sorry, we were unable to load..."? Or having trouble accessing a certain page in the Editor? Do pages not load as you expect?

Maybe you see something that looks like this:

This article helps you troubleshoot Editor-loading issues.

Here are some common issues:

The Optimizely Desktop App solves many common Editor loading issues, including the ones above. Consider installing it if you're having trouble with the web application.

See a different problem? We'll walk you through more troubleshooting steps below.

Editor loading issues, step by step

  1. First, check that your page loads consistently outside of Optimizely. Make sure you can reach the page in your browser outside of Optimizely, multiple times in a row. If the page doesn't load outside of Optimizely, it may not load in Optimizely either.

  2. Try clearing your browser cache and cookies. Then, reload the page. Sometimes, this is the easiest way to resolve an Editor-loading issue.

  3. Next, check that the Optimizely snippet is installed.

    In Optimizely Classic, check the Diagnostic Report to make sure the snippet is installed and properly configured.

    In Optimizely X, there's no diagnostic report yet -- we're working on that! Here's how to check for the snippet. First, open the browser console. Then, type optimizely. If an error is returned such as "optimizely is undefined," the snippet isn't implemented correctly.

    Here's how to implement the snippet. Make sure the snippet is installed synchronously and at the top of your <head> tag.

  4. Advanced: Are there any errors in the JS console that don't 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.

  5. Advanced: Is your site configured to disallow parameters it doesn't expect, or parameters that include raw URLs in them?

    Check this by trying 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'll need to whitelist Optimizely's Editor parameters. Contact support if you'd like to know more about this. Or, try the Optimizely Desktop App.

  6. Advanced: Does the page load 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 won't load in an arbitrary iFrame, you may need to whitelist the Optimizely domain ( as a valid host. Or, try the Optimizely Desktop App.

Load or hide modals in the Editor in Optimizely Classic

Sometimes, you may need to edit a modal that doesn't show up in the Optimizely Editor. Or, you may need to edit content that's hidden behind a modal. 

Editor-only code lets you display or hide modals in the Editor. Everything inside the editor_only code executes in the Optimizely Editor, but it doesn't execute outside the Editor when the experiment is live.

/* _optimizely_evaluate=editor_only */
/* _optimizely_evaluate=end_editor_only */
// Write your variation code below

If you’ve had a look at the steps above and you haven’t been able to load your page in the editor correctly yet, you can also try our Optimizely Editor Loading Chrome extension.