ResizeObserverSize

Resize observer resize-observer

Baseline: Widely available on the web, in every major browser since Jul 2020, and long enough to count on (since Jan 2023).

niso: Partial 53%. 68 of 127 subtests pass, by system: Linux 53%, macOS 53%. Engines: QuickJS, the engine niso's WPT run uses; Node and Porffor have no recorded run. WPT results recorded at f3b4fa8, 2026-11-10; web-features 3.45.0. WPT tests · niso's support · ResizeObserver, ResizeObserverEntry, ResizeObserverSize

ResizeObserverSize is an interface in idl/resize-observer.webidl, exposed in Window. What it does is on MDN; this page says what niso has of it.

Status

The web features its members belong to, each with its Baseline status on the web and how much of the feature’s WPT suite passes in niso (see Web platform support).

Feature	On the web	In niso	Members
Resize observer	Widely available	Partial 53% 68 of 127 subtests pass	3

Members

inlineSize

attribute

readonly attribute unrestricted double inlineSize;

int32_t niso_resize_observer_size_get_inline_size(niso_dom* dom, niso_handle self, double* out);

blockSize

attribute

readonly attribute unrestricted double blockSize;

int32_t niso_resize_observer_size_get_block_size(niso_dom* dom, niso_handle self, double* out);