Specifying image dimensions (width and height) will help to speed up your website. Now I will write about how to add the width and height attributes in image <img> tag  for opencart, and I'm using opencart version 2.0 for this tutorial. Add Image Dimension Function in System First step it will add image dimension function in system file, and it will add the function code to 'startup.php' in system folder. so open the startup.php file and add following code in the bottom of file: function imgSize($output) {    preg_match('/-[0-9]*x[0-9]*\.(gif|jpg|png|jpeg)/i', $out..