When to use
Buttons use a variety of sizes, colors, and iconography combinations.
Use a Button to enable actions or decisions that are important to a user. They should be used throughout your UI, it can be used in situations where users need to :
submit a form,
confirm a change,
begin/create a new task,
trigger a new element to appear on the page,
specify a new or next step in a process.
Button is used for actions, like ‘Load more’, ‘Filters’ etc.
Links for links.
When not to use
Do not use buttons as navigational elements. Instead, use links when the desired action is to take the user to a new page (with the exception of the back and forward buttons).
Do not use Links for actions, only for links.
Do not style Buttons as links.
Do not use two icons at the same time.
...
Writing labels
...
Do
Button labels use sentence case (Capitalize the first letter, use lowercase for everything else) and are as short as possible
...
For maximum legibility, a text label should remain on a single line. Find another label if you can’t do it !
...
Combining button styles
...
Do
When using multiple buttons, you can place an outlined primary button next to a primary button.
...
Use several primary buttons it will loose emphasis.
...
Stretched buttons on mobile
...
Do
Keep mobile margin with stretched button on mobile.
...
Use full screen with stretched button on mobile.
...
Alignment
Button alignment by default should be left-aligned. However, buttons can appear center-aligned or right-aligned if required.
...
Right alignment is normally saved for forms, stepped submissions, or simple Icon with Label hyperlinks.
...
Disabled/inactive Buttons
Inactive buttons can be used to communicate to the user that a certain action would be possible if circumstances were different, such as entering an email address in a text field prior to signing up.
...