Always within reach
Hoober (2013) found most people hold phones one-handed and use the thumb, and Bergstrom-Lehtovirta and Oulasvirta (2014) placed the comfortable thumb area low on the screen. On long product pages a buy button only at the end forces scrolling; a sticky button keeps it in the thumb zone. In Fogg's (2009) model it is a prompt always available when motivation peaks.
Size, width and safe areas
Parhi et al. (2006) set adequate one-handed thumb sizes, and per Fitts (1954) wider targets are faster, so full width with side margins and at least 48dp height is common. Add safe-area padding to avoid the iPhone home indicator. On input screens, lift the button above the keyboard or tie it to the keyboard's done key following mobile form usability.
Obscuring and experimentation
Pad the bottom of the page by the button's height so final content is not hidden. WCAG 2.2 (W3C, 2023) criterion 2.4.11 forbids sticky elements fully hiding focused items. With bottom navigation the base grows thick, so hiding navigation in focused flows such as checkout can help. Test effects (Kohavi et al., 2009) and watch guardrails such as returns alongside conversion rate optimization metrics.
FAQ
- Should every screen have one?
- No; it works when a screen has one clear primary action and wastes space on browsing screens.
- How does it differ from a floating action button?
- Sticky buttons usually span the bottom; FABs are small round buttons floating over content.
Sources reviewed: 2026-10-27
References
- Hoober, S. (2013, February 18). How do users really hold mobile devices? UXmatters. Shows one-handed thumb use is most common.
- Bergstrom-Lehtovirta, J., & Oulasvirta, A. (2014). Modeling the functional area of the thumb on mobile touchscreen surfaces. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 1991–2000). ACM. Thumb functional-area model for button placement.
- Parhi, P., Karlson, A. K., & Bederson, B. B. (2006). Target size study for one-handed thumb use on small touchscreen devices. In Proceedings of MobileHCI 2006 (pp. 203–210). ACM. Minimum thumb target sizes.
- Fitts, P. M. (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47(6), 381–391. Wide, near targets are faster.
- Fogg, B. J. (2009). A behavior model for persuasive design. In Proceedings of the 4th International Conference on Persuasive Technology (Article 40, pp. 1–7). ACM. Frames the sticky button as a prompt.
- Kohavi, R., Longbotham, R., Sommerfield, D., & Henne, R. M. (2009). Controlled experiments on the web: Survey and practical guide. Data Mining and Knowledge Discovery, 18(1), 140–181. Guide to validating changes with online experiments.
- World Wide Web Consortium. (2023). Web Content Accessibility Guidelines (WCAG) 2.2. Criterion 2.4.11: focus not obscured by sticky content.