Buttons are a familiar UX tool and an essential part of the users' journey. Visual cues help people determine whether or not a button is clickable, so make sure to use proper visual signifiers on clickable elements so they look and function like buttons.

Size according to Fitts

Fitts Law is a UX principle that says you should make buttons big enough that they’re easy to click/tap and keep the distance short between the action and the action button.

A good rule of thumb from MIT Touch Labs: make your buttons a minimum of 10mm x 10mm. Make buttons mobile responsive and resize with percentage widths.

Color

The primary action on a page carries a stronger visual weight and should be the visually dominant button. Secondary actions (like Cancel or Go Back) should have less visual attraction.

A button is multi-state, therefore, consider the hover/tap states and active states of the button.

Shape

Effective button style is square with no corner radius or has rounded corners, depending on the site/app brand. Maintain consistency across controls so your user recognizes button elements.

Placement

Use standard UI patterns because conventional button placement improves discoverability. Using a standard layout will help users understand the purpose of each element - even if there is a button without other strong visual signifiers. Combining a standard layout with clean visual design and ample whitespace is better design.

Call to Action or CTA

UX button microscopy tells users what action will happen if they click the button. For effective calls-to-action, minimize word count: Use "Add to Cart" or "Submit" to make things easy for users.