# mercurius > Fastify GraphQL adapter with subscription support Latest version **16.10.1** (published 2026-09-26) · MIT license · 0 weekly downloads ## Install ```sh npm install mercurius pnpm add mercurius yarn add mercurius bun add mercurius ``` ## Health **Score 65/100 (B)** — status: active. Positive: has types; no vulnerabilities; recently updated; high maintenance score; high quality score. Warnings: low downloads; no esm support. ## Facts | | | |---|---| | Version | 16.10.1 | | Published | 2026-09-26 | | First published | 2015-11-17 | | Weekly downloads | 0 | | License | MIT | | TypeScript types | bundled | | Module format | CommonJS | | Node | ^20.9.0 \|\| >=22.0.0 | | Dependencies | 14 | | Unpacked size | 734.9 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 2490 | | Author | Matteo Collina | | Maintainers | matteo.collina, jonnydgreen | ## Links - npm: https://www.npmjs.com/package/mercurius - Repository: https://github.com/mercurius-js/mercurius - Homepage: https://mercurius.dev - Issues: https://github.com/mercurius-js/mercurius/issues - npm.io page: https://npm.io/package/mercurius ## Dependencies (14) - [ws](https://npm.io/package/ws.md) ^8.2.2 - [p-map](https://npm.io/package/p-map.md) ^4.0.0 - [tiny-lru](https://npm.io/package/tiny-lru.md) ^11.0.0 - [mqemitter](https://npm.io/package/mqemitter.md) ^7.0.0 - [quick-lru](https://npm.io/package/quick-lru.md) ^7.0.0 - [graphql-jit](https://npm.io/package/graphql-jit.md) 0.8.9 - [@fastify/error](https://npm.io/package/@fastify/error.md) ^4.0.0 - [fastify-plugin](https://npm.io/package/fastify-plugin.md) ^6.0.0 - [@fastify/static](https://npm.io/package/@fastify/static.md) ^10.1.0 - [readable-stream](https://npm.io/package/readable-stream.md) ^4.0.0 - [secure-json-parse](https://npm.io/package/secure-json-parse.md) ^4.1.0 - [single-user-cache](https://npm.io/package/single-user-cache.md) ^2.0.0 - [@fastify/websocket](https://npm.io/package/@fastify/websocket.md) ^11.0.0 - [safe-stable-stringify](https://npm.io/package/safe-stable-stringify.md) ^2.3.0 ## Recent versions - 16.10.1 (latest) — 2026-09-26 - 15.0.0 (next) — 2024-09-09 - 8.13.2 (eight) — 2023-01-10 - 16.10.0 — 2026-07-14 - 16.9.0 — 2026-04-03 - 16.8.0 — 2026-03-06 - 16.7.0 — 2026-01-19 - 16.6.0 — 2025-11-13 - 16.5.0 — 2025-10-10 - 16.4.0 — 2025-09-30 - 16.3.0 — 2025-09-25 - 16.2.0 — 2025-06-19 - 16.1.0 — 2025-02-24 - 16.0.1 — 2025-01-14 - 16.0.0 — 2024-12-21 - … 113 more at https://npm.io/package/mercurius/versions ## README ![Mercurius Logo](https://raw.githubusercontent.com/mercurius-js/graphics/main/mercurius-horizontal.svg) # mercurius [![CI workflow](https://github.com/mercurius-js/mercurius/actions/workflows/ci.yml/badge.svg)](https://github.com/mercurius-js/mercurius/actions/workflows/ci.yml) [![NPM version](https://img.shields.io/npm/v/mercurius.svg?style=flat)](https://www.npmjs.com/package/mercurius) [![NPM downloads](https://img.shields.io/npm/dm/mercurius.svg?style=flat)](https://www.npmjs.com/package/mercurius) [![neostandard javascript style](https://img.shields.io/badge/code_style-neostandard-brightgreen?style=flat)](https://github.com/neostandard/neostandard) Mercurius is a [**GraphQL**](https://graphql.org/) adapter for [**Fastify**](https://www.fastify.io) Features: - Caching of query parsing and validation. - Automatic loader integration to avoid 1 + N queries. - Just-In-Time compiler via [graphql-jit](http://npm.im/graphql-jit). - Subscriptions. - Federation support via [@mercuriusjs/federation](https://github.com/mercurius-js/mercurius-federation), including Subscriptions. - Gateway implementation via [@mercuriusjs/gateway](https://github.com/mercurius-js/mercurius-gateway), including Subscriptions. - Batched query support. - Customisable persisted queries. ## Docs - [Install](#install) - [Quick Start](#quick-start) - [Examples](#examples) - [API](docs/api/options.md) - [Context](docs/context.md) - [Loaders](docs/loaders.md) - [Hooks](docs/hooks.md) - [Lifecycle](docs/lifecycle.md) - [Federation](docs/federation.md) - [Subscriptions](docs/subscriptions.md) - [Batched Queries](docs/batched-queries.md) - [Persisted Queries](docs/persisted-queries.md) - [TypeScript Usage](/docs/typescript.md) - [HTTP](/docs/http.md) - [GraphQL over WebSocket](/docs/graphql-over-websocket.md) - [Integrations](docs/integrations/) - [Related Plugins](docs/plugins.md) - [Security - CSRF Prevention](docs/security/csrf-prevention.md) - [Faq](/docs/faq.md) - [Contributing](#contributing) - [Acknowledgements](#acknowledgements) - [License](#license) ## Install ```bash npm i fastify mercurius graphql # or yarn add fastify mercurius graphql ``` The previous name of this module was [fastify-gql](http://npm.im/fastify-gql) (< 6.0.0). ## Quick Start ```js 'use strict' const Fastify = require('fastify') const mercurius = require('mercurius') const app = Fastify() const schema = ` type Query { add(x: Int, y: Int): Int } ` const resolvers = { Query: { add: async (_, { x, y }) => x + y } } app.register(mercurius, { schema, resolvers }) app.get('/', async function (req, reply) { const query = '{ add(x: 2, y: 2) }' return reply.graphql(query) }) app.listen({ port: 3000 }) ``` ## Examples Check [GitHub repo](https://github.com/mercurius-js/mercurius/tree/master/examples) for more examples. ## Contributing Mercurius is an **OPEN Open Source Project**. This means that: > Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project. See the [CONTRIBUTING.md](https://github.com/mercurius-js/mercurius/blob/master/CONTRIBUTING.md) file for more details. ## Acknowledgements The project is kindly sponsored by: - [NearForm](https://www.nearform.com) - [Platformatic](https://platformatic.dev) The Mercurius name was gracefully donated by [Marco Castelluccio](https://github.com/marco-c). The usage of that library was described in https://hacks.mozilla.org/2015/12/web-push-notifications-from-irssi/, and you can find that codebase in https://github.com/marco-c/mercurius. ## License MIT --- _Source: https://npm.io/package/mercurius · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._