Errors / JavaScript errors

ResizeObserver loop completed with undelivered notifications

A part of the page resized itself while being measured; almost always harmless.

Rarely any: at worst a flicker as the layout settles.

Why it happens

• A ResizeObserver callback changed the size of what it observes, so the browser deferred the rest of the notifications to the next frame and reported it.
• Common with charts, rich text editors, virtualised lists and UI libraries that measure themselves.
• Older Chrome said ResizeObserver loop limit exceeded.

How to fix it

1. Usually nothing: the layout settles on the next frame. Filter it out of error tracking.
2. If something visibly jumps, move the size change in the callback into requestAnimationFrame.
3. It is reported through window.onerror with no stack and no file, so error trackers such as Sentry count it as a real error; most already ignore it by default. When it appears thousands of times a day, look at which component observes itself and changes its own size, since each loop costs a frame.

Whose problem it is

Either the site's own code or a third party's, depending on where it comes from.