Mock Service Worker

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.

Mock Service Worker is listed with 1 API on the APIs.io network. Tagged areas include API Mocking, GraphQL, HTTP, Mock Servers, and Mocking.

The Mock Service Worker catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

Mock Service Worker’s developer surface includes documentation, getting-started guide, GitHub presence, code examples, engineering blog, and 12 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

18.6/100 emerging ▬ flat Agent 2/100 human only Front door AI 1/6 silent Heartbeat 100/100 alive Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreemium

1 API

API Mocking GraphQL HTTP Mock Servers MockingService WorkerTesting WebSocket

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 18.6/100 · emerging

Contract Quality 2.8 / 21

Developer Ergonomics 4.9 / 17

Access Clarity 1.3 / 17

Operational Transparency 1.5 / 11

Contract Governance 1.0 / 10

Discoverability 4.9 / 9

Regulatory Posture 1.6 / 15

Agent readiness — 2/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document
MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes

11 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 13.2 — up to +21.7 composite points
Access Clarity scores 7.9 — up to +18.4 composite points
Developer Ergonomics scores 28.6 — up to +14.3 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/mock-service-worker/apis.yml: open an issue on github.com/api-evangelist/mock-service-worker to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Standards implemented 3

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

GraphQL

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

HTTP

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

WebSockets

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

APIs 1

Individual APIs this provider publishes, each with its own machine-readable definition.

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...

GraphQL 1

GraphQL schemas published by this provider.

Mock Service Worker GraphQL API

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...

GRAPHQL

Mock Service Worker API pricing

Not yet checked against Mock Service Worker's own pricing page. Compiled by API Evangelist on 2026-05-04; confirm before you rely on a figure. A free plan or tier is listed.

Plan	Price
Free freemium	Free
Professional paid	Free
Enterprise enterprise	—

Plan details, limits and sources →

Rate limits

Free Tier Default: 10 requests per minute
Free Tier Monthly Quota: 1000 requests per month
Professional Tier Default: 100 requests per minute

Compiled by API Evangelist, not yet checked against Mock Service Worker's documentation. All 5 limits →

Pricing Plans 1

Published pricing tiers and plan structures.

Mock Service Worker Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Mock Service Worker Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Mock Service Worker Finops

FINOPS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Mock Service Worker Context

4 classes · 0 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Mock Service Worker — jsonschema rules

5 rules · 3 warnings 2 info

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions for this provider's data models.

Mock Service Worker Handler

0 properties

JSON SCHEMA

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Mock Service Worker Domain Security

TLSv1.3 · HSTS

SECURITY

Resources

Get Started 1

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

JSONSchema

JSONSchema

Design & Contract 1

Pagination, idempotency, versioning, errors, and events

JSONLD

JSONLD

Build 3

SDKs, sample code, and the tooling you integrate with

GitHub

GitHub

Examples

Examples

NPM

NPM

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 2

Status, limits, changes, and where to get help

RateLimits

RateLimits

Discord

Discord

Commercial 3

Pricing, plans, and the legal terms of use

Plans

Plans

FinOps

FinOps

License

License

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 2

Properties that don't map to a standard resource type

Sponsor

Sponsor

OpenCollective

OpenCollective

Source (apis.yml)

aid: mock-service-worker
name: Mock Service Worker
description: 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.
type: Index
deliveryModel:
  model: unknown
  license_evidence:
    not_product:
    - mswjs/msw
  open_source: unknown
  commercial: false
  callable_host: false
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - repository-not-product
  generated: '2026-09-25'
  method: derived
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: low
  source:
  - plans
  - security
  generated: '2026-11-06'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/mock-service-worker.png
url: https://raw.githubusercontent.com/api-evangelist/mock-service-worker/refs/heads/main/apis.yml
x-docs-platform: vitepress
x-docs-platform-confidence: medium
x-docs-platform-checked: 2026-10-04
tags:
- API Mocking
- GraphQL
- HTTP
- Mock Servers
- Mocking
- Service Worker
- Testing
- WebSocket
tags_raw:
- API Mocking
- GraphQL
- HTTP
- Mock Server
- Mocking
- Service Worker
- Testing
- WebSocket
access: 3rd-Party
position: Consuming
created: '2025-01-08'
modified: '2026-04-28'
specificationVersion: '0.23'
apis:
- aid: mock-service-worker:msw
  name: Mock Service Worker
  description: 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 environments and setupServer for Node.js, with handlers
    (http, graphql, ws, sse) that allow developers to declare mocked responses without modifying application code.
  image: https://mswjs.io/static/logos/msw-logo.svg
  humanURL: https://mswjs.io/
  tags:
  - API Mocking
  - GraphQL
  - HTTP
  - Mocking
  - Service Worker
  - Testing
  - WebSocket
  properties:
  - type: Documentation
    url: https://mswjs.io/docs/
  - type: GettingStarted
    url: https://mswjs.io/docs/quick-start
  - type: HTTP Handler
    url: https://mswjs.io/docs/network-behavior/rest
  - type: GraphQL Handler
    url: https://mswjs.io/docs/network-behavior/graphql
  - type: WebSocket Handler
    url: https://mswjs.io/docs/network-behavior/websocket
  - type: GitHub
    url: https://github.com/mswjs/msw
  - type: Examples
    url: https://github.com/mswjs/examples
  - type: NPM
    url: https://www.npmjs.com/package/msw
  - type: License
    url: https://github.com/mswjs/msw/blob/main/LICENSE.md
  - url: graphql/mock-service-worker-graphql.md
    type: GraphQL
  contact:
  - FN: MSW Maintainers
    url: https://github.com/mswjs/msw
common:
- type: Plans
  url: plans/mock-service-worker-plans-pricing.yml
- type: RateLimits
  url: rate-limits/mock-service-worker-rate-limits.yml
- type: FinOps
  url: finops/mock-service-worker-finops.yml
- type: DomainSecurity
  url: security/mock-service-worker-domain-security.yml
- type: Website
  url: https://mswjs.io/
- type: Documentation
  url: https://mswjs.io/docs/
- type: GettingStarted
  url: https://mswjs.io/docs/quick-start
- type: GitHub
  url: https://github.com/mswjs/msw
- type: Examples
  url: https://github.com/mswjs/examples
- type: NPM
  url: https://www.npmjs.com/package/msw
- type: Discord
  url: https://kettanaito.com/discord
- type: Sponsor
  url: https://github.com/sponsors/mswjs
- type: OpenCollective
  url: https://opencollective.com/mswjs
- type: License
  url: https://github.com/mswjs/msw/blob/main/LICENSE.md
- type: JSONLD
  url: json-ld/mock-service-worker-context.jsonld
- type: JSONSchema
  url: json-schema/mock-service-worker-handler-schema.json
- type: Integrations
  url: https://mswjs.io/ecosystem
- url: https://mswjs.io/rss.xml
  type: Blog
integrations:
- name: Data
- name: Source
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
  url: https://apievangelist.com

Mock Service Worker API — frequently asked questions

Does Mock Service Worker have an API?

Yes. APIs.io lists 1 API from Mock Service Worker, including Mock Service Worker.

How much does the Mock Service Worker API cost?

APIs.io lists 3 pricing plans for Mock Service Worker, with each plan's price, limits and inclusions under Pricing on this page.

Is the Mock Service Worker API ready for AI agents?

Mock Service Worker has a Kin Score of 18.6 out of 100 (emerging) and an Agent Readiness score of 1.9 (human-only), scored by API Evangelist on 2026-11-06.

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apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
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