How to add automatic class in image for wordpress post

Question

I want to make a responsive theme with Bootstrap 3. However, I need to automatically add the CSS class .img-responsive to every post image because I need the i

Answer 1

Classes are not added on upload, but when the image is sent to the editor. You can use the image_send_to_editor filter to add one or more classes. This example adds a fancybox class.