If you upload images via the WordPress image uploader and insert it into your post, it will include the image width and height attribute in the html <img> tag. Here’s what it will look like.

<img src="path/to/your/image" width="123" height="456" class="aligncenter size-full" alt="" title="">

In most cases, this is absolutely alright. However, if you are using a responsive theme or are dealing with responsive web design, the “width” and “height” attribute will be a major roadblock that you need to get rid of.

Here’s how you can do it.

1. Open your theme’s functions.php file.

2. Copy and paste the following code:

add_filter( 'post_thumbnail_html', 'remove_width_attribute', 10 );
add_filter( 'image_send_to_editor', 'remove_width_attribute', 10 );
 
function remove_width_attribute( $html ) {
    $html = preg_replace( '/(width|height)=\"\d*\"\s/', "", $html );
    return $html;
}

3. Save the changes.

That’s it. Next time when you insert image into the post via the WP image uploader, the width and height attribute will no longer be there.