tc39/proposal-shadowrealm resource

Health v2 · maintenance only

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Adoption not part of the score

1583 stars · 69 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

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

learning-resource · maturity experimental

interpreter security sdk programming-languages security developer-tools cross-platform browser ecmascript tc39 javascript-proposal shadowrealm specification stage-2-7 realms sandboxing reference-implementation javascript specifications web-server nodejs

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