# que-etc/resize-observer-polyfill

A polyfill for the Resize Observer API

Repository: https://github.com/que-etc/resize-observer-polyfill
Canonical: https://ross.abutalabs.com/products/resize-observer-polyfill
Language: JavaScript
License: MIT
License Family: permissive
Topics: resize-observer, ponyfill, polyfill, resize-events
Last push: 2023-01-27T12:16:31+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 3684, "days_push": 1314, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1752, forks 130 (observed 2026-08-28T04:05:31.725718+00:00)

## What it is
A lightweight (2.44 KiB gzipped) polyfill/ponyfill for the browser Resize Observer API, implemented with MutationObserver and Mutation Events fallbacks. It lets JavaScript code observe element size changes without polling, including changes from CSS transitions, animations, and pseudo-classes.

## Use cases
- observe element size changes in browsers lacking ResizeObserver support
- react to element resizing caused by CSS transitions or animations
- detect size changes from dynamic pseudo-classes like :hover
- support legacy browsers like IE9-IE11 with resize observation
- use ResizeObserver as a ponyfill without modifying the global object

## When to choose
- you need ResizeObserver functionality in older browsers (IE9+, older Safari/Firefox)
- you want a tiny, spec-compliant ponyfill that avoids global object pollution
- your app must react to size changes without polling or modifying observed elements

## When to avoid
- your target browsers all natively support ResizeObserver
- you need a maintained library with ongoing updates (last release Jan 2023)
- you need to observe size changes in non-DOM environments like Node.js

## Facets
- artifact type: library
- maturity: maintenance
- function: ui-components, developer-tools
- domain: web-development, frontend, browser-extensions
- platform: browser, cross-platform
- tags: resize-observer, polyfill, ponyfill, dom, javascript, mutation-observer

## Member repositories
- que-etc/resize-observer-polyfill (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:31.725718+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:28:27.603247+00:00, confidence not recorded.
  - readme: https://github.com/que-etc/resize-observer-polyfill (fetched 2026-08-28T04:05:31.725718+00:00, sha d678b09201f5)
  - registry_npm: https://registry.npmjs.org/resize-observer-polyfill (fetched 2026-08-29T11:06:37.006691+00:00, sha aabc53c1d093)
- Data as of 2026-08-30T08:39:29.467469+00:00.