mastodon/app/assets/javascripts/components/components/loading_indicator.jsx

const LoadingIndicator = () => {
  const style = {
    textAlign: 'center',
    fontSize: '16px',
    fontWeight: '500',
    color: '#616b86',
    paddingTop: '120px'
  };

  return <div style={style}>Loading...</div>;
};

export default LoadingIndicator;