# systemjs/systemjs

Dynamic ES module loader

Repository: https://github.com/systemjs/systemjs
Canonical: https://ross.abutalabs.com/products/systemjs
Language: JavaScript
License: MIT
License Family: permissive
Last push: 2026-06-14T00:09:51+00:00

## Health v2 (maintenance only)
Score: 62/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 87, release rhythm 8, longevity 100
- inputs: {"age_days": 4859, "days_push": 81, "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 13093, forks 1093 (observed 2026-08-28T04:11:02.125052+00:00)

## What it is
SystemJS is a hookable, standards-based ES module loader for browsers. It transpiles production ES module builds into the System.register format so they run in older browsers (down to IE11) with near-native speed, supporting dynamic import, top-level await, import maps, and live bindings.

## Use cases
- load ES modules in browsers that don't support them natively
- run Rollup code-splitting builds in legacy browsers
- support dynamic import and top-level await in older browsers
- use import maps with Content Security Policy in legacy environments
- load multiple module formats in the browser at runtime

## When to choose
- you must support legacy browsers like IE11 with ES module workflows
- you need a hookable runtime module loader with import maps and module types
- you run micro-frontend or dynamic module loading setups in the browser

## When to avoid
- your target browsers all support native ES modules
- you only need a bundler or package manager rather than a runtime loader
- you build for Node.js only

## Facets
- artifact type: library
- maturity: stable
- function: build-tool, developer-tools
- domain: web-development, frontend, developer-tools
- platform: browser
- tags: module-loader, es-modules, system-register, import-maps, browser-compatibility, code-splitting, polyfill, javascript, nodejs

## Member repositories
- systemjs/systemjs (main) score 62

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:11:02.125052+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 2026-08-29T17:13:32.150861+00:00, confidence not recorded.
  - readme: https://github.com/systemjs/systemjs (fetched 2026-08-28T04:11:02.125052+00:00, sha 457097d99cc1)
- Data as of 2026-08-30T08:39:29.467469+00:00.