One of the most widely used front-end web development frameworks is Bootstrap. It already has a predefined CSS style and JS bundle to speed up the creation of web pages. You can browse through the most popular code snippets or do a search. You can even create your own original code in a text editor and execute it instantly. Try resizing the preview panel using the resize handler to observe how responsive it is. The default loading of the Bootstrap Code editor and JS library in the preview window eliminates the need to explicitly load files. Visit the website for further detail.