# tc39/proposal-shadowrealm

ECMAScript Proposal, specs, and reference implementation for Realms

Repository: https://github.com/tc39/proposal-shadowrealm
Canonical: https://ross.abutalabs.com/products/proposal-shadowrealm
Homepage: https://tc39.es/proposal-shadowrealm/
Language: HTML
License Family: other
Last push: 2025-02-10T20:52:02+00:00

## Health v2 (maintenance only)
Score: 35/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 6, release rhythm 35, longevity 100
- inputs: {"age_days": 3793, "days_push": 569, "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 1583, forks 69 (observed 2026-08-28T04:05:07.299241+00:00)

## What it is
A TC39 ECMAScript language proposal (currently at Stage 2.7) for the ShadowRealm API, which provides distinct global environments with their own intrinsics and built-ins. The repository contains the specification text, explainer documents, presentations, and a reference implementation for the proposed API.

## Use cases
- evaluate JavaScript code in an isolated global environment
- run untrusted scripts in a sandboxed realm with separate intrinsics
- import values from modules into an isolated execution context
- create a fresh JavaScript global object without page reload
- track the standardization status of the ShadowRealm proposal
- implement or polyfill the ShadowRealm API in a JavaScript engine
- understand how wrapped functions cross realm boundaries

## When to choose
- you need to evaluate code in a fresh, isolated global environment with its own built-ins
- you are building a plugin or scripting system that must sandbox user-supplied code from host intrinsics
- you want to follow or contribute to the TC39 standardization of Realms
- you need a reference implementation or spec text to prototype ShadowRealm support in an engine

## When to avoid
- you need a production-ready, standardized API - the proposal is still at Stage 2.7 and subject to change
- you need full process isolation or OS-level sandboxing - ShadowRealm isolates globals, not memory or resources
- you need a stable polyfill for browsers today - native support is not yet shipped broadly
- you want a general-purpose sandboxing or security tool rather than a language specification

## Facets
- artifact type: learning-resource
- maturity: experimental
- function: interpreter, security, sdk
- domain: programming-languages, security, developer-tools
- platform: cross-platform, browser
- tags: ecmascript, tc39, javascript-proposal, shadowrealm, specification, stage-2-7, realms, sandboxing, reference-implementation, javascript, specifications, web-server, nodejs

## Member repositories
- tc39/proposal-shadowrealm (main) score 35

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:07.299241+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 2026-08-30T03:56:07.231830+00:00, confidence not recorded.
  - readme: https://github.com/tc39/proposal-shadowrealm (fetched 2026-08-28T04:05:07.299241+00:00, sha cdde9715dee0)
  - homepage: https://tc39.es/proposal-shadowrealm/ (fetched 2026-08-29T11:26:30.204474+00:00, sha 45d10f8967b7)
- Data as of 2026-08-30T08:39:29.467469+00:00.