# Centered vs Left-Aligned Form Layout A/B Test

Page: https://alidemirbas.com.tr/en/lab/ab-test-library/tests/centered-vs-left-aligned-form-layout-ab-test

## Hypothesis

If the supporting information stays accessible in both arms, the centered layout may pull ahead on form completion rate by gathering attention in a single column. If visitors need reassurance while filling in the form, the left-aligned layout could earn more submissions because it keeps that content beside the form in reading order.

## When to run this test

On desktop, heatmaps showing interest drifting away from the form, session recordings of visitors moving back and forth between form and explanation, or visitors who leave without touching the first field can mean the form does not hold attention or that visitors look for reassurance while filling it in. Whichever layout leads should get more first-field entries and more submissions. Build the centered arm so the page scrolls normally instead of pinning the form to the vertical middle of the screen; if drop-off comes from field count or validation, look at those first.

## Primary metric

**Form completion rate**: Compare successful submissions to see whether alignment affects completion.

## Other metrics

- **Form start rate**: Measure visitors who begin the first field after seeing the form.
- **Form completion time**: Compare time from form start to successful submission.
- **Supporting-content click-through rate**: Track visitors who open explanatory or reassurance content; an open does not prove it was read.
- **Page exit rate**: Compare page exits among visitors assigned to the form.

## What to check before and during the test

- **Alignment**: Compare left- and center-aligned forms on the same page.
- **Content**: Keep explanations, reassurance and summary information accessible in both arms.
- **Dimensions**: Keep form width, fields and validation unchanged.
- **Device**: Exclude device layouts where both arms look the same.
- **Separate test**: Removing support content or changing form width is a separate test.

## What to watch when reading the result

- Pair form completion rate with form start rate and page exit rate; if first-field entries rise but submissions do not, do not call the layout a winner. Supporting-content click-through rate only hints at where attention goes, and opening that content does not mean it was read.
- Leave out device layouts where both arms look the same; if the mobile layout does not change, do not report a difference there as a mobile lift. Since the result covers only the form on this page, test again before applying it to forms with a different purpose.
- Excluding identical layouts shrinks eligible traffic, so the test may take longer than you expect. Get the sample per variant from the [sample size calculator](https://alidemirbas.com.tr/en/calculators/sample-size-calculator) and divide it by each arm's share of the daily traffic that actually sees different layouts to estimate the run time. A difference that stays unclear is not proof that the layouts perform the same; base the choice on reasons outside the test, such as consistency with your other forms.

## Frequently Asked Questions

### What happens to side information when centering the form?

Keep explanations, assurances and summaries accessible in both arms. Removing them while changing alignment introduces another treatment that must be defined separately.

### What if both arms look identical on mobile?

Define eligible layouts before launch. Identical mobile renderings do not measure a mobile alignment effect. Preserve ordinary scrolling rather than vertically locking the form.

### How should help-content interaction be interpreted?

Opening help is diagnostic and does not establish reading. Use form completion as the primary outcome and avoid generalizing between forms serving different tasks.