Flicker
When a visitor briefly sees the original page before a test's change replaces it.
Also called flash of original content
Flicker happens when a testing script changes the page after it has already painted. Besides looking broken, it can bias the test: visitors who notice the swap may behave differently.
Tools prevent it by applying changes before the first paint, or by briefly hiding the elements a test changes until it is applied.
A visitor sees the old headline for a third of a second before the new one appears.
Related terms
- A/B testAn experiment that shows two versions of a page to randomly split visitors and compares which one performs better on a chosen goal.
- Split URL testA test that sends part of the traffic to a different URL, such as a redesigned landing page, and compares the outcomes.
- Sample ratio mismatch (SRM)When the number of visitors in each variant differs from the planned split by more than chance can explain: a sign the test is broken.