The primary button is always used for the most important actions. Two primary actions can't be near each other.
The secondary button is always use for secondary actions. Several secondary actions can be near by each other.
The link button is mainly used for Cancel actions.
The default size is a height of 40px. It is used for main page actions such as Save or Cancel.
The small size is a height of 32px. It is used for actions inside a page, such as dropdowns, button groups, and split buttons.
Dos and Don'ts
Use the same height for all the buttons that are in the same row.
Characters can not all be uppercase in a button.
Text can not wrap multiple lines. It must all be on one line.
A borderless button must be placed either before or after a set of bordered buttons.
A secondary borderless button is used in toolbars when a secondary button would be too heavy for the toolbar's design. This keeps the design clean.
Buttons can display icons instead of text. The icons, however, must be monospaced inside the button. Icon buttons are used primarily in management bars. This button variation can be primary, secondary, or borderless type.
Icon and text button
This button type is only used in sites, outside of administration. The icon emphasizes and helps communicate the action. The label must match the icon's purpose.
Block level button
Buttons can also be configured at block level. Use this configuration when you need to communicate that an important action is required for the user. For example, it can be used as a load more action below a list. Please do not use it in forms. Choose the button type carefully. Primary is not always the best choice, nor is it the only configuration.
Dropdown buttons are always used with a dropdown menu. This button variation can be secondary or borderless type.
Split buttons are used when you need to offer the user a quick main action along with secondary actions.
Button groups are used to switch between complementary views for example, but they must never be used for complementary actions, "Change and Cancel" actions, or "Save and Cancel" actions. In those cases, single buttons are the correct solution.
Plus buttons provide add actions for a dataset and are normally placed in toolbars. The add button lets you add entities, such as a blog post for a blog, a message board thread for a message board, or a folder. It can have one action or multiple. Visit Dropdown menu > Sorting actions to learn more.
Action buttons are used when a set of contextual actions are needed for an element or a dataset. This button displays a set of actions inside a dropdown menu. The actions must be sorted in a specific way. please visit Dropdown menu > Sorting actions to learn more.