Ali Demirbaş - Lab
TRGet in touch

Forms & Signup

Testing a Taller Input Field Height on a Form

Taller input fields provide larger touch targets and may make mobile entry easier.

  • Forms & signup
  • Form completion rate

Control vs Variant

The same element, larger or smaller.

Changed
Size
Page
Forms & signup
Difference
changed

Hypothesis

They also lengthen the form and reduce how many fields fit on screen. Compare completion while keeping font size and spacing unchanged.

How to run this test

Primary metric

Form completion rate

Compare successful submissions to see whether taller fields affect completion.

Other metrics

  • Form start rateCompare visitors who begin the first field after seeing the form.
  • Form completion timeMeasure time from form start to successful submission.
  • Validation error rateTrack input and validation errors that may relate to field height.

What to check before and during the test

  • HeightIncrease field height by a predefined amount.
  • Keep constantKeep font size, spacing between fields, field width, order and validation unchanged.
  • Touch inputMeasure mobile input errors the same way in both arms.
  • DensityRead start and abandonment rates alongside the number of fields visible at once.
  • DeviceReview desktop and touch devices separately.

Setup mistakes to avoid

  1. 1Do not change field height and font size together.
  2. 2Do not change spacing between fields along with their height; these are separate variables.
  3. 3Do not reduce touch targets below the accessibility minimum; that is not a test option.
  4. 4Do not infer mobile touch behavior from desktop results.
  5. 5If larger fields reduce the number visible on screen, review form starts as well as completion.