Are WP images responsive by default?

It’s change automatically change image while image’s in responsive mode.We can add all images here so it’s cut automatically with screen size.

add_action( 'after_setup_theme', 'wpdocs_theme_setup' );
function wpdocs_theme_setup() {
 add_image_size( 'category-thumb', 300 ); // 300 pixels wide (and unlimited height)
 add_image_size( 'homepage-thumb', 220, 180, true ); // (cropped)
}