This article will help you:
  • Figure out why pages might not load in the Editor
  • Get rid of the "Compatibility Mode" dialog that appears in the Editor
  • Troubleshoot mixed-content issues

Is your page not loading correctly in Optimizely for another reason? Check our article on Editor Loading for more solutions!

When you load a page in the Optimizely Editor, you may see a warning that reads: "We have loaded your site using compatibility mode — you can still edit your page, but some site functionality might be missing."

Optimizely Editor loads your site in compatibility mode when it's not able to load all of the content on your page. As a result, some styling and content may not display correctly, and content in iFrames may not render in the Editor. If you have insecure (HTTP) content being loaded into a secure (HTTPS) page or frame, it may be blocked. 


This warning only affects the Optimizely Editor, not your live site.


Your browser's security settings may block mixed content, or insecure (HTTP) content being loaded into a secure (HTTPS) page or frame like the Optimizely Editor. If you don't want to disable your browser's security settings, the only way to ensure that your content is not blocked is to load your page securely via HTTPS.

If you'd like to jump straight into how to override compatibility mode, find your browser below: 

How compatibility mode works

In September 2013, Internet Explorer, Chrome and Firefox implemented a new default setting that blocks "active mixed content." This is a security feature that prevents secure (HTTPS) websites from being attacked. If an HTTPS page has insecure (HTTP) content inside of it and that content is “active” (i.e. JavaScript or CSS), then the insecure active content can be intercepted, compromised, and used to glean data from the secure (HTTPS) part of the page. 

Why does this affect how Optimizely Editor loads sites?

If an insecure (HTTP) site that you load into the Optimizely Editor is compromised, it can compromise your Optimizely account. Optimizely’s Editor is always loaded securely via HTTPS to protect your experiments and data.

When loading your site, Optimizely will attempt to load both HTTP and HTTPS versions of the page; if both of these fail, we will attempt to load your website through our proxy server. We will prefer the HTTPS version of the site to the HTTP version if no protocol is specified. If you wish to load only the HTTP version, make sure to include the full URL (i.e. when you create the experiment.

If you try to load an insecure site (e.g. instead of into Optimizely’s Editor, your browser may trigger a mixed content warning and block the insecure site from loading. This is because the Optimizely Editor’s protocol is HTTPS, and the page you’re trying to load is HTTP. 

Note that the browser warning is meant only to advise you that an insecure site (your page) is being loaded inside a secure site (the Editor). Optimizely will show a message in the main canvas of the Editor if we detect that mixed content is being blocked, though we may not always be able to detect this: 

How to override compatibility mode

If you use Optimizely’s Editor often, you may wish to override the mixed content warning. Note that doing this will affect all sites visited in your browser, not just Optimizely.

Google Chrome

Chrome for Mac (or Linux)

  1. Quit Chrome if you have it open.
  2. Open Terminal, accessible from the Applications folder.
  3. Type the following command into Terminal to load Chrome:
/Applications/Google\\ Chrome --user-data-dir=/tmp/tempchrome --allow-running-insecure-content --incognito &

Using this command will allow mixed content to run in all tabs in the incognito window opened. Please only use this incognito window for using Optimizely, and use your original instance of Chrome for all other web browsing.


To make a shortcut, run the command below. You can then locate that file within your Applications folder and double click to open:

echo "/Applications/Google\\ Chrome --user-data-dir=/tmp/tempchrome --allow-running-insecure-content --incognito &" > /Applications/Insecure\ Chrome.command && chmod +x /Applications/Insecure\ Chrome.command

Chrome for Windows

  1. Right-click the Chrome icon that you wish to modify, and select Properties.
  2. In the Target field, add the command line flag following ‘chrome.exe’ as follows:
    chrome.exe --allow-running-insecure-content
  3. Click OK to save, and launch Chrome from that shortcut.

For further instructions, please see the Chromium website.

Mozilla Firefox

If you want to disable mixed content for this session only, click the lock icon in the URL address bar.

Then click the arrow on the right to access the Disable Protection for Now option.

If you want to disable mixed content for all future sessions on all sites, follow this process:

  1. Type about:config in the address bar (where you type in a website URL) and press the Enter key.
  2. Click the I’ll be careful, I promise! button

  3. In the search field that appears, type block_active
  4. Double-click the field security.mixed_content.block_active_content which will set its value to false.

Internet Explorer

If you want to disable mixed content for this session only, click Show all content at the bottom of the window.

If you want to disable mixed content for all future sessions on all sites, follow this process:

  1. Click the wrench icon to open Internet Explorer's settings.
  2. Select Security > Internet Zone > Miscellaneous > Custom level…
  3. Select Enable for Display mixed content


As of Safari 9, all mixed content is blocked by default -- only HTTPS or compatibility mode pages can load into the Editor. If you are running into issues with Safari, we recommend using Chrome. 


Still see the compatibility warning after trying these steps? If the Optimizely editor loads your site in compatibility mode after you’ve allowed active mixed content, there may be other reasons why we can’t fully load your page content. If this is the case, check out this troubleshooting article.