Compatibility mode warning and mixed content in the editor

  • Updated
  • Optimizely Web Experimentation
  • Optimizely Performance Edge

When you load a page in the Optimizely Web Experimentation editor, you may see a warning at the top of the editor that reads: "We have loaded your site using compatibility mode—you can still edit your page, but some site functionality might be missing" or "You're in Compatibility Mode." This compatibility mode message means you may be encountering an issue with mixed content.


You can use the Optimizely Web Experimentation desktop app instead of the browser app to avoid the compatibility mode issue (and take advantage of additional features like device emulation). If you are attempting to load gated content, site that requires a login, see Cannot load a password-protected, gated, or session-specific page in the editor.

Compatibility mode is triggered when your browser's security settings block mixed content or keep insecure (HTTP) content from being loaded into the Optimizely Web Experimentation editor's secure (HTTPS) page. As a result, there are two ways you can avoid compatibility mode and prevent the Optimizely Web Experimentation editor from blocking insecure content:

What is compatibility mode?

In September 2013, Internet Explorer, Chrome and Firefox implemented a new default setting that blocks "active mixed content." This is a security feature to prevent secure (HTTPS) websites from being attacked. If an HTTPS page contains insecure (HTTP) content and that insecure content is “active” (that is, JavaScript or CSS), the insecure active content can be intercepted, compromised, and used to glean data from the secure part of the page. To prevent this, these browsers use a default setting to block insecure (HTTP) content that's loaded into a secure (HTTPS) page or frame.

Resolve compatibility mode in Google Chrome browsers

Compatibility mode can usually be resolved in a Google Chrome browser by clicking the shield icon at the end of the URL address bar and loading "unsafe scripts" and reloading the page.

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If the shield icon is not present or if allowing "unsafe scripts" does not resolve compatibility mode, download the Optimizely Experimentation editor Assistant Chrome extension. When the extension is successfully enabled on your Chrome browser, click the extension and enable Strip X-Frame-Options Header and reload the page.


Disable browser security settings

One way to avoid compatibility mode is to disable your browser's security settings. 

Google Chrome for Mac or Linux

  1. Quit Chrome (if you have it open).
  2. Open Terminal.
  3. Enter the following command into Terminal to open a Chrome incognito window:
    /Applications/Google\\ Chrome --user-data-dir=/tmp/tempchrome --allow-running-insecure-content --incognito &
Using this command lets mixed content run in all tabs in the incognito window that opens. Use this incognito window only for Optimizely Web Experimentation. Use another original instance of Chrome for all other web browsing.

Google Chrome for Windows

  1. Right-click the Chrome icon that you want to modify.
  2. Select Properties.
  3. In the Target field, add the command line flag after ‘chrome.exe’ as follows:
    chrome.exe --allow-running-insecure-content
  4. Click OK to save.
Use this Chrome shortcut only for Optimizely Web Experimentation. Use another original instance of Chrome for all other web browsing.

Mozilla Firefox

Mixed content blocking in Firefox (scroll down to "Unblock mixed content" for instructions).

Internet Explorer

"Only secure content is displayed" notification in Internet Explorer 9 or later.


As of Safari 9, all mixed content is blocked by default. If you use Safari, you can only load HTTPS or compatibility mode pages into the editor. If you are having compatibility mode issues with Safari, you should use Chrome instead.

Insecure content triggers compatibility mode

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

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

The Optimizely Web Experimentation editor loads your site in compatibility mode when mixed content is blocked and the editor cannot load all of the content on your page. This is when you see the warning "We have loaded your site using compatibility mode."

The compatibility mode warning advises you that an insecure site (your page) is being loaded inside a secure site (the editor). Optimizely Web Experimentation displays the warning in the main canvas of the editor if it detects that mixed content is being blocked, although it may not always be able to detect this.

Compatibility mode affects your site

Compatibility mode means the Optimizely Web Experimentation editor will not display blocked mixed content. When the Optimizely Web Experimentation editor loads your site in compatibility mode, some styling and content may not display correctly in the editor. Content in iFrames may not render in the editor.

The compatibility mode warning only affects the content displayed in the Optimizely Web Experimentation editor, not your live site.

Troubleshoot other page-loading issues