Modern best practice dictates that the width and height attributes must always be added to the <img> tags to ensure sufficient space is allocated on the page before the browser starts fetching images. This minimizes reflow and re-layout and improves Cumulative Layout Shift.

<img src="/puppy.jpg" width="640" height="360" alt="Puppy with balloons" />
                        

If any of these attributes are missing, JCH Optimize will add them using the Add Image Attributes feature.

Add image attributes

The values for the width and height are obtained by checking the actual dimensions of the image on the server in pixels.

	Warning
	If the images are not shown on screen at their actual dimensions and the width and height are not set in the CSS then enabling this feature can show the page distorted as the browser attempts to render them at the dimensions indicated in the width and height attributes. In this case resize your images or disable this feature.