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

Not quite sure how good this answer is performance wise but it works. Just put this in functions.php.

function img_responsive($content){
    return str_replace('

Please note that you need the space after class="img-responsive so it doesn't merge with other classes.