# Mock Service Worker

**Canonical:** https://apis.io/providers/mock-service-worker/  
**Website:** https://mswjs.io/  
**APIs profiled:** 1

Mock Service Worker (MSW) is an industry-standard, open-source API mocking library for the browser and Node.js. MSW intercepts outgoing requests at the network level using Service Workers in browsers and a request interception algorithm in Node.js, allowing developers to write client-agnostic mocks for HTTP, GraphQL, WebSocket, and Server-Sent Events and reuse them across any framework, tool, or environment for development, testing, and debugging.

## Kin Score — 20.7 / 100 (emerging)

Scored 2026-08-20 under rubric 0.12.0. Trend: flat (+0.0 from 20.7).

| Facet | Score |
|---|---|
| Discoverability | 68.5 |
| Contract Quality | 8.5 |
| Governance | 9.8 |
| Contract Governance | 9.8 |
| Operational Transparency | 13.2 |
| Developer Ergonomics | 28.6 |
| Commercial Clarity | 15.8 |
| Access Clarity | 15.8 |

## Agent readiness — 4.5 (human-only)

| Dimension | Value |
|---|---|
| Spec Presence | no |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | no |
| Auth Clarity | no |
| Idempotency | no |
| Error Semantics | no |
| OpenAPI Examples | documented |
| Rate Limit Signal | documented |
| Event Surface Described | no |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## Access

Freemium — onboarding: unknown, pricing: freemium, trial: no (confidence: medium).

## APIs (1)

- **Mock Service Worker** — Mock Service Worker (MSW) is an open-source library for mocking REST, GraphQL, WebSocket, and Server-Sent Events APIs at the network level. It provides setupWorker for browser e...

## Security (1)

- **Mock Service Worker Domain Security** — TLSv1.3 · HSTS

## Plans (1)

- **Mock Service Worker Plans Pricing**

## Tags

API Mocking, GraphQL, HTTP, Mock Server, Mocking, Service Worker, Testing, WebSocket

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/mock-service-worker/). Scores are computed from the provider's own public artifacts under a published rubric.