Strip Image Classes from HTML Output

Take a closer look at get_image_tag() which can take a lot of parameters like $id, $alt, $title, $align, $size.

If you look even closer you’ll find the get_image_tag_class filter to change the image class names (like class, ID, align and size).

You can use the filter within your functions.php like this:

Note: This will still return an empty tag like: class=""

function strip_image_class($class, $id, $align, $size) {
    return '';
}
add_filter('get_image_tag_class', 'strip_image_class', 0, 4);

Update: To completely remove everything related to the class you’ll have to filter the $html:

function strip_entire_image_class($html) {
    return preg_replace('/ class="(.*)"https://wordpress.stackexchange.com/", '', $html);
}
add_filter('get_image_tag', 'strip_entire_image_class', 0, 4);