Case study
Sticky CTA case study: 252.9% more mobile order completions in a 20-day test
This sticky CTA case study shows what happened when an eCommerce landing page kept its call to action on screen at all times. On mobile, the rate of order completion and revenue per visitor both rose 252.9% at 98% confidence. On desktop, nothing changed, so the sticky bar went live on mobile only.
Sticky CTA case study at a glance
| Client | An eCommerce store (not named in the original case study) |
|---|---|
| Vertical | eCommerce |
| Page tested | A landing page |
| Change tested | A sticky call to action that stays on screen while the visitor scrolls |
| Test | A/B test, 20 days, mobile and desktop analyzed separately |
| Metrics | Conversion rate (orders per visitor) and revenue per visitor |
| Outcome | Rolled out on mobile; no change on desktop |
+252.9%
Rate of order completion on mobile, 20-day test
Source: Sticky CTA test, mobile visitors, 20 days, 98% confidence
What is a sticky CTA?
A sticky CTA is a call-to-action button or bar that stays fixed on the screen, usually along the bottom edge of a phone, while the visitor scrolls the page. Instead of scrolling back up to find the button, the visitor can act from anywhere on the page. On product pages it is often called a sticky add to cart.
In this test the sticky CTA was a slim bar pinned to the bottom of the screen, with one short line of text and one button. The rest of the landing page stayed the same.
What problem was the sticky CTA meant to solve?
The sticky CTA was meant to make the next step easier to reach. On a long landing page, the main call to action sits in one place. Once a visitor scrolls past it to read more, the button is gone, and acting means scrolling back to find it. Each extra scroll is a small chance to lose the sale.
That cost is highest on a phone. A phone screen shows a small slice of the page at a time, so a button leaves the screen after a swipe or two, and the visitor who is ready to buy has to hunt for it.
What was the hypothesis?
The hypothesis was that a call to action visible at every point on the page would help more visitors move on to the next step, and that this would show up as more completed orders and more revenue per visitor. The team also wanted to know whether the effect differed between mobile and desktop, so the two were analyzed separately from the start.
What changed on the page?
The variation added a bar fixed to the bottom of the screen: a short line inviting the visitor to act and a full-width button below it. The bar stayed in place as the visitor scrolled, so the call to action was never more than one tap away. Nothing else on the page was changed.
How was the sticky CTA tested?
The sticky CTA was tested against the original landing page for 20 days. The team tracked two metrics, the conversion rate (orders per visitor) and revenue per visitor, and analyzed mobile and desktop visitors separately to see whether the bar helped on one, both or neither.
| Device | Rate of order completion | Revenue per visitor | Confidence | Decision |
|---|---|---|---|---|
| Mobile | +252.9% | +252.9% | 98% | Rolled out |
| Desktop | No significant change | No significant change | Not significant | Not rolled out |
What were the sticky CTA results?
On mobile, the sticky CTA raised the rate of order completion by 252.9% and revenue per visitor by 252.9% over the 20-day test, at a 98% confidence level. On desktop, neither metric changed significantly. Convertica recommended putting the sticky CTA live on mobile only.
The two mobile figures are identical, and that says something useful. Revenue per visitor is the conversion rate multiplied by the average revenue per order. If both rose by the same amount, the average order in the variation was about the same size as in the control: the sticky CTA brought more people to the end of the purchase, not bigger baskets.
Read the size of the lift with care. The original case study does not publish the number of visitors or the starting conversion rate, and a very large percentage lift usually means the starting rate was low. The direction of the result and the gap between devices are the most reliable lessons here.
Why did the sticky CTA work on mobile but not desktop?
The original case study does not give a reason, but screen size is the most likely one. On a phone, a normal button leaves the screen after a swipe or two, so a fixed bar restores something visitors had lost. On a desktop screen, more of the page is visible at once and the main button stays in view for longer, so a second, sticky copy adds less.
The wider lesson from the original write-up is that each device deserves its own approach. A change that wins on mobile can be neutral on desktop, and averaging the two together can hide a real win. Desktop visitors may need a different change entirely, such as clearer copy near the main button, rather than the same bar.
How to test a sticky CTA on your own site
You can run a sticky CTA test on any long page where visitors scroll past the main button: product pages, landing pages and long sales pages. Keep the bar small, keep its action identical to the main button, and judge it by device on orders and revenue, not clicks.
- Check where the button goes. Scroll your page on a phone and note how soon the main call to action leaves the screen. If it disappears in the first swipe, a sticky CTA is worth testing.
- Copy the main action exactly. The sticky button should do the same thing as the main one, with the same words. A second, different offer splits attention.
- Keep it slim. One short line and one button. A bar that takes a large share of a small screen hides the content people are reading.
- Never cover anything that matters. The bar should not sit over form fields, the on-screen keyboard, chat widgets or consent banners, and it should not hide the element a keyboard user has focused (WCAG 2.2 success criterion 2.4.11, Focus Not Obscured).
- Segment by device from the start. Set up the test so mobile and desktop are reported separately, as this one was.
- Measure orders and revenue per visitor. More clicks on a bar mean little if orders do not follow.
- Roll out only where it wins. Here that meant mobile only.
Before you start, the A/B test sample size calculator shows how much mobile traffic a test like this needs, and the statistical significance calculator checks the result. A sticky button is also part of the redesign in the product page redesign case study, and the mobile slider case study is another test where a mobile-only change paid off.
Does a sticky CTA matter for AI shopping agents?
Not directly. An AI agent reading your page does not scroll or lose sight of a button, so a sticky bar gives it nothing. What matters for an agent is that the call to action is a real link or button in the page's HTML, with a clear label, and not something drawn only by a script. If your sticky bar duplicates a proper button, people and agents are both served. Agent readiness is one of the eight checks in Convertica's free CRO audit.
Sticky CTA case study FAQ
What is a sticky CTA?
A sticky CTA is a call-to-action button or bar that stays fixed in place, usually at the bottom of a phone screen, while the visitor scrolls. The next step is always one tap away instead of scrolling back to find it. It is also called a sticky button, a sticky bar or, on product pages, a sticky add to cart.
Does a sticky CTA increase conversions?
It can, but not everywhere. In this test, a sticky CTA raised the mobile rate of order completion 252.9% in 20 days at 98% confidence, and made no significant difference on desktop. The same element helped one device and did nothing on the other, so test it per device rather than assume it works.
How long did the sticky CTA test run?
The test ran for 20 days. Conversion rate (orders per visitor) and revenue per visitor were measured separately for mobile and desktop visitors. The mobile result reached a 98% confidence level. The desktop result showed no significant change in either metric.
Why did the sticky CTA work on mobile but not on desktop?
The original case study does not say. The likely reason is screen size: on a phone, a normal button scrolls out of view after a swipe or two, so a fixed bar puts back something visitors had lost. On a wide desktop screen the main button stays visible for longer, so a sticky copy adds less.
Why are the conversion rate and revenue per visitor lifts the same?
Revenue per visitor is the conversion rate multiplied by the average revenue per order. When both rise by the same 252.9%, the average order value in the variation was about the same as in the control. The sticky CTA brought more buyers, not bigger orders.
Should I add a sticky add to cart button to my store?
Test it on mobile first. Keep the bar short, use the same action as your main button, make sure it never covers content, form fields or the keyboard, and measure orders and revenue per visitor by device. Roll it out only on the devices where it wins.
Can Convertica run this kind of test on my store?
Convertica starts with the free CRO audit, an app that checks your page for people and for AI agents while you watch. After it, if you want the fixes built for you, the one page rebuild covers one page and the full site rebuild covers your whole site: Convertica's team builds every fix the audit found.
