Analytics dictionary › FOOC

What is FOOC

FOOC or Flash of Original Content is a situation in Javascript based A/B testing where the experiment is causing an element on the page to flicker when changing from original to the variation.

FOOC in A/B Testing
FOOC in A/B Testing

In the example above, you can see the FOOC effect of a very simple A/B test that is changing the hero copy of the services page.

Why FOOC is a problem?

First of all, it is annoying for the visitors. No one likes when the look of the website is flickering too much while the page loads.

Second, and the most important reason is that it could easily skew the results of your A/B tests (and not in your favor).

By default, all of the most popular A/B testing tools have some sort of FOOC when they apply the changes on your website, but there are some workarounds that could make the effect less noticeable.

How to reduce FOOC?

Luckily, there are ways you can make the effect of FOOC less noticeable. Here’s an overview of the most popular ones that almost anyone could apply:

  • Install you A/B testing tool as recommended
  • Hide content before the changes have been applied
  • Follow the general front-end development best practices
  • Consider back-end A/B testing solutions

Want to know more? Take a look at this article.

FOOC and other loading-time-related issues will not leave Javascript-based A/B testing anytime soon. There are ways to lower the chance of letting it skew your results but to be 100% sure you should consider moving to one of the server-side A/B testing solutions.

Last modified: August 29, 2017

Want to see more articels like What is FOOC? Check out all definitions in the Analytics Dictionary.

Sign up for Reflective Data

5,000 sessions / month ×

Please enter your email


After submitting your email, we will send you the registration form.