# w3c/IntersectionObserver

Intersection Observer

Repository: https://github.com/w3c/IntersectionObserver
Canonical: https://ross.abutalabs.com/products/intersectionobserver
Homepage: https://www.w3.org/TR/intersection-observer/
Language: Bikeshed
License: NOASSERTION
License Family: other
Last push: 2026-03-19T21:25:41+00:00

## Health v2 (maintenance only)
Score: 65/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 73, release rhythm 35, longevity 100
- inputs: {"age_days": 4093, "days_push": 167, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases, no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3613, forks 509 (observed 2026-08-28T04:08:11.696618+00:00)

## What it is
The W3C specification repository for the Intersection Observer browser API, written in Bikeshed, which defines how web pages efficiently observe visibility of DOM elements relative to the viewport. The formerly included polyfill is archived and no longer maintained since all major browsers ship native implementations.

## Use cases
- detect when an element scrolls into the viewport
- implement lazy loading of images
- track ad or content viewability
- trigger animations on scroll
- learn how the Intersection Observer API works
- implement infinite scroll

## When to choose
- you need the authoritative spec text for IntersectionObserver behavior
- you are implementing the API in a browser engine
- you want to check browser support and status of the standard

## When to avoid
- you need a polyfill for older browsers - it is archived and unsupported
- you want a runnable library rather than a specification document
- you need element visibility tracking outside the browser DOM

## Facets
- artifact type: learning-resource
- maturity: active
- function: browser-extension, ui-components, web-scraping
- domain: web-development, frontend, browser-extensions, documentation
- platform: browser
- tags: web-standard, specification, intersection-observer, polyfill-archived, w3c, dom-api, lazy-loading, scroll-visibility, web-server

## Member repositories
- w3c/IntersectionObserver (main) score 65

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:11.696618+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 2026-08-29T18:33:38.156841+00:00, confidence not recorded.
  - readme: https://github.com/w3c/IntersectionObserver (fetched 2026-08-28T04:08:11.696618+00:00, sha b621d967cb4f)
- Data as of 2026-08-30T08:39:29.467469+00:00.