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.

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 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.

The Optimizely X editor is more stable than the Classic editor but is still subject to the same loading issue.  Most issues will arise from NOT seeing a HELLO or READY response in the console logs.  Editor workflow can be found in Optimizely X Transition notes:

HELLO is sent as soon as p13n_inner.js establishes communication with editor_frame module and is still awaiting Editor client and its data

If you see:

[Loader] HTTP Failed to respond with HELLO after 15000ms
[Loader] HTTPS Failed to respond with HELLO after 15000ms
[Loader] PROXY Failed to respond with HELLO after 15000ms


  • p13n_inner script may not have downloaded
  • Snippet may not be on page or is outdated
  • Look for innie.js loading in network 

READY is sent once p13n_inner.js has been initialized with Editor Client and its data

  • If you see HELLO,  but no editor data look for:

Optly/Initialized with data 

  • If you see:  [Loader] Editor client bootstrapped - Editor client got its data and has been initialized 
  • Check the network requests for:
    • Production Client
    • innie.js
    • p13n_inner.js
    • Editor Client
    • Editor Data

Additional Notes: 

  •  Project JS conflicts can cause issues between p13n_inner and editor client/data

  • There is a 15000ms timeout for HELLO response but there is no time out for READY for HTTP or HTTPS (spins forever) - this might indicate one of these:

    • A fatal JS conflict

    • A page that loads the Optimizely snippet async and disables Optimizely when it fails to load within a certain timeframe

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