What is CTR (click-through rate) in advertising?

Short answer. CTR, click-through rate, is the percentage of people who click an ad after seeing it: clicks divided by impressions. 5 clicks from 100 impressions is a 5% CTR. It tells you whether an ad earns a click, not whether the click turns into an install or a purchase.

Definition

Google Ads defines CTR as "a ratio showing how often people who see your ad or free product listing end up clicking it." AppsFlyer puts it the same way for mobile: "CTR is the number of clicks on a mobile ad in relation to total views."

Formula

CTR = clicks / impressions (multiply by 100 for a percentage)

Google gives the example directly: "if you had 5 clicks and 100 impressions, then your CTR would be 5%."

Worked example (illustration)

These are made-up round numbers. Ad A: 100,000 impressions, 1,500 clicks, CTR 1.5%, 300 installs. Ad B: 100,000 impressions, 800 clicks, CTR 0.8%, 400 installs. Ad A wins on CTR and loses on installs: its clicks convert at 20%, Ad B's at 50%. Judged on CTR alone you would scale the wrong ad.

What a good or bad reading tells you

Google notes that "a high CTR is a good indication that users find your ads and listings helpful and relevant," and also that "a good CTR is relative to what you're advertising and on which networks." AppsFlyer calls a low CTR "a leading indicator of a campaign that may not be targeting the right audience or delivering the right message," but warns that CTR "doesn't paint the full picture and should never serve as a sole indicator of success."

High CTR with low conversion usually means the ad promises something the next screen does not deliver: a store page, an end card or a landing page that breaks the promise. A CTR that falls over weeks on the same ad is a common sign of creative fatigue.

We give no benchmark CTR. AppsFlyer's own view is that "there's no magic number that determines a good CTR versus a bad one."

How it is used in app, game and brand advertising

On Google Search, CTR feeds into expected CTR, which Google says "is a component of Ad Rank." In app and game UA, CTR is a diagnostic next to IPM, which carries the result. For consumer brands, CTR and hook rate show whether the ad stops people; purchases show whether it sells.

Common mistakes

1. Optimising for CTR and getting curiosity clicks that never convert.
2. Comparing CTR across placements. In-app interstitials, feeds and search behave differently.
3. Reading CTR without the conversion rate after the click.

Flixr's view

Our view is that CTR is a diagnostic, not an outcome, which is the point of measure creative on purchases, not on the ad. Our own tool calls winners by what the networks keep funding rather than by what got clicks. And when CTR is high but sales are not, the fix is often the page, not the ad: a hook is a promise, and most landing pages break it.