CRO Glossary
Click-Through Rate (CTR)
The percentage of people who click a specific link, button, or ad out of everyone who saw it.
Click-through rate is calculated as clicks divided by impressions (or views), expressed as a percentage. It's one of the most widely used metrics in both advertising and on-site experimentation because it's easy to measure and gives a fast read on whether creative, copy, or placement is capturing attention.
The important caveat is that CTR measures interest, not necessarily value — a test that boosts CTR on a promotional banner might just be attracting clicks from people who bounce immediately afterward, rather than driving actual conversions or revenue. For that reason, CTR is best treated as a leading indicator or a guardrail metric to monitor alongside a primary, further-downstream success metric like signups or purchases, rather than as the sole measure of a test's success.
For example, a headline test on a blog might show Variant B getting a 15% higher CTR into an article, but if those readers have a much higher bounce rate once they arrive, the 'win' on CTR could actually represent a mismatch between the headline's promise and the article's content.
Related terms
Above vs Below Median Split
A segmentation technique that divides users into two groups at the median of a metric to compare high and low engagers.
Qualitative Feedback Loop
A recurring process of collecting and acting on user comments, session recordings, and survey responses to inform test hypotheses.
Experiment Metadata
The structured record of who, what, when, and how for a test — hypothesis, owner, dates, variants, and metrics used to track and audit it.
Pre-Test Analysis
The upfront work of validating traffic, metrics, and baseline data quality before launching an experiment.
Above-the-Fold vs Below-the-Fold Messaging Hierarchy
How the order and prominence of value-proposition messaging is split between the visible screen and the rest of the page.
Experiment Contamination
When a control or variant group is unintentionally exposed to the other condition, corrupting the comparison.
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