The normal .css is better for development in normal coding. if you want to edit with the content in the .css file, but if you are not want to modify the file, use the .min.css for slightly better performance. The main difference between bootstrap.min.css and bootstrap.css is spacing because In the bootstrap.min.css file all the white spaces have been removed ( minified version ), where In the bootstrap.css file white spaces are not removed, So obviously file size will be larger as compared to bootstrap.min.css. For that reason, As Developers, We should use bootstrap.min.css.