Reflow

The browser redoing layout after a size or position change.

What is a reflow?

A reflow is the browser redoing layout after something changes size or position. Doing it too often makes a page feel slow.

// slow: reads and writes in a loop cause a reflow each time
items.forEach(el => { el.style.width = el.offsetWidth + 10 + "px"; });

Level: Master · More CSS terms at this level

Updated September 27, 2026