To create a spinner/loader, use the .spinner-border class:

Colored Spinners

Use any text color utilites to add a color to the spinner:

Growing Spinners

Use the .spinner-grow class if you want the spinner/loader to grow instead of "spin":

Spinner Size

Use .spinner-border-sm or .spinner-grow-sm to create a smaller spinner:

Spinner Buttons

Add spinners to buttons: