Why Do I Notice a Page Flicker When the VWO Test Page is Loading?

You may, at times, notice a page flicker. (See control for a split second before the variation loads). The following are some possible reasons for the page flicker:

• The VWO SmartCode was added via a tag manager: When using a tag manager to load the VWO code, ensure that the tag manager is set to Synchronous code. When the tag manager is set to Asynchronous code, your visitors might see a flicker in the variations loaded. This means that when visitors are supposed to see a variation, they will see the control page for a moment before the changes appear, as the code is loaded by the tag manager. As a best practice, you should manually add the VWO SmartCode directly to your campaign pages. Reach out to VWO support for any assistance.
  For example, VWO supports integration with the Tealium tag manager flawlessly when Tealium settings are configured with Synchronous code.
  
  
• JS code changes causing the page to flicker: If visitors use only the operations supported by the visual editor, VWO knows the exact elements modified and hides them until a variation change is loaded. But if you add a JavaScript code snippet to change some elements on the web page, you might notice a flicker—original content will flash before the change is applied—on the live site. To minimize the flicker, add the following code snippet to your VWO editor:

  //This code snippet allows VWO to keep the body hidden while the changes 
  are being applied.
  vwo_$("body").vwoCss({"visibility":"visible !important"});

• The VWO SmartCode is added to the bottom of the webpage and not in the header: If the VWO SmartCode is added at the end of the web page, the browser executes the VWO code only in the end. In the meantime, you may notice a flash of the original (or control) page before you see the variation page. Ensure that the VWO code snippet is added to the header of the web page.
  
  
• Change image operation: If you add large-sized images to the variation, the images may take some time to download on the page. Until the images are downloaded, old images/content continue to be displayed. This might appear like a page flicker to the visitors. You can reach out to VWO support for any queries.