# guybedford/es-module-shims

Shims for new ES modules features on top of the basic modules support in browsers

Repository: https://github.com/guybedford/es-module-shims
Canonical: https://ross.abutalabs.com/products/es-module-shims
Language: JavaScript
License: MIT
License Family: permissive
Last push: 2026-08-17T06:22:08+00:00

## Health v2 (maintenance only)
Score: 97/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 98, release rhythm 95, longevity 100
- inputs: {"age_days": 2920, "days_push": 16, "days_rel": 38, "gap_med": 6.0, "n_releases_24m": 29}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1729, forks 99 (observed 2026-08-28T04:05:28.485854+00:00)

## What it is
A browser polyfill library that adds modern ES modules features like import maps, JSON/CSS/Wasm modules, import defer, and TypeScript type stripping on top of native browser ESM support. It bypasses processing for browsers with native import maps support and uses a fast WASM-based lexer to rewrite module specifiers only for older browsers.

## Use cases
- use import maps in browsers that don't support them natively
- polyfill JSON and CSS module imports with import assertions
- load WebAssembly modules via source phase imports
- use import defer syntax with a fallback for older browsers
- strip TypeScript types directly in the browser
- implement custom module resolution and fetch hooks
- hot reload ES modules with an import.meta.hot API

## When to choose
- you rely on import maps or newer module features but must support older browsers
- you want a no-build, browser-native module workflow with polyfill fallbacks
- you need custom loader hooks for in-browser module resolution or transforms

## When to avoid
- you only target browsers with full native import maps support
- you use a bundler-based build pipeline that doesn't need module polyfills

## Facets
- artifact type: library
- maturity: active
- function: developer-tools
- domain: web-development, frontend, browser-extensions
- platform: browser
- tags: es-modules, import-maps, polyfill, javascript-modules, wasm-modules, -modules, css-modules, typescript-stripping, loader-hooks, hot-reloading

## Member repositories
- guybedford/es-module-shims (main) score 97

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:28.485854+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 2026-08-30T03:31:57.063591+00:00, confidence not recorded.
  - readme: https://github.com/guybedford/es-module-shims (fetched 2026-08-28T04:05:28.485854+00:00, sha c7ec86b5ad5e)
- Data as of 2026-08-30T08:39:29.467469+00:00.