Decide the `loading` attribute affected by the above fold aka onscreen critical contents. <ul><li>`lazy`, the default: defers loading below fold or offscreen images and iframes until users scroll near them.</li><li>`auto`: browser determines whether or not to lazily load. Only if uncertain about the above fold boundaries given different devices. </li><li>`eager`: loads right away. Similar effect like without `loading`, included for completeness. Good for above fold.</li><li>`defer`: trigger native lazy after the first row is loaded. Will disable global `No JavaScript: lazy` option on this particular field, <a href=':defer'>read more</a>.</li><li>`unlazy`: explicitly removes loading attribute enforced by core. Also removes old `data-[SRC|SRCSET|LAZY]` if `No JavaScript` is disabled. Best for the above fold.</li><li>`slider`, if applicable: will `unlazy` the first visible, and leave the rest lazyloaded. Best for sliders (one visible at a time), not carousels (multiple visible slides at once).</li></ul><b>Note</b>: lazy loading images/ iframes for the above fold is anti-pattern, avoid, <a href=':url' target='_blank'>read more</a>.