Custom property cycle

Custom properties that depend on each other in a loop.

What is a custom property cycle?

A custom property cycle is when custom properties depend on each other in a loop. The browser treats them all as invalid.

.box {
  --a: var(--b);
  --b: var(--a);   /* a loop: both become invalid */
}

Level: Master · More CSS terms at this level

Updated September 27, 2026