ResizeObserver loop 🟨 JavaScript

ResizeObserver loop completed with undelivered notifications.

A ResizeObserver callback changed layout in a way that triggered another resize in the same frame.

Seen on: JavaScript

Meaning

It is usually a benign warning reported by browsers (and surfaced as an error by dev overlays/Sentry). It becomes a problem only if it causes visible jitter.

Common causes

  • Resize callback changing the size of the observed element
  • UI libraries (charts, editors, grids) adjusting layout
  • Infinite resize ping-pong

⚡ Quick fix

  1. Defer changes with requestAnimationFrame inside the callback
  2. Ignore it in error monitoring if harmless
  3. Avoid resizing the observed element from its own callback

Detailed fix by platform

JavaScript

  1. new ResizeObserver(entries => requestAnimationFrame(() => layout(entries)));

How to diagnose

  1. Impact — Any visible flicker?
  2. Source — Your code or a library?

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