@ynode/versionify

Copyright (c) 2026 Michael Welter me@mikinho.com

A simple and lightweight Fastify plugin to expose your application's name and version from package.json.

It automatically handles content negotiation to respond with JSON, HTML, or plain text based on the client's Accept header. Version responses include weak ETags by default and honor If-None-Match with 304 Not Modified.

Supported media ranges include exact types and standard wildcards: application/json and application/* return JSON, text/html returns HTML, text/plain returns plain text, text/* returns the first supported text response, and */* falls back to JSON.

For each representation, the most-specific matching media range determines its quality. An explicit q=0 exclusion therefore takes precedence over a broader wildcard.

Fastify automatically exposes a matching HEAD endpoint for the plugin's GET route. It returns the negotiated status and headers without a response body.

Installation

Install the package and its required peer dependency, fastify.

npm install @ynode/versionify fastify

Options

You can pass an options object as the second argument to register.

Option	Type	Default	Description
prefix	string	undefined	Optional Fastify route prefix beginning with /.
path	string	"/version"	The URL path to expose the version endpoint. Must begin with /.
pkg	object	undefined	A package.json object. If not provided, the plugin will automatically load package.json from your project root.
rootDir	string	process.cwd()	Directory whose package.json is loaded when pkg is not provided.
cacheMaxAge	number	3600	Cache-Control max-age in seconds. Set to 0 to disable.
metadata	object	undefined	Additional static key-value pairs included in the JSON response. Keys name, version, and build are reserved and will be ignored; build metadata belongs in the dedicated build option.
build	object	undefined	Additional build metadata nested under build in the JSON response. Valid Dates become ISO strings, invalid Dates become null, and BigInts become strings.
etag	boolean	true	Emit weak ETags and honor If-None-Match conditional requests.
requireIdentity	boolean	false	Reject registration unless the resolved package name and version are non-empty strings.
routeOptions	object	undefined	Allowlisted Fastify schema, config, logLevel, onRequest, preValidation, and preHandler settings for the version route.

Basic Usage

import versionify from "@ynode/versionify";

// Register the plugin with default options
await fastify.register(versionify, { prefix: "/~" });

Example with Options

import versionify from "@ynode/versionify";

// Register with a custom path
await fastify.register(versionify, {
    path: "/info",
});

Now the endpoint will be available at http://localhost:3000/info.

For deployments where fallback identity would hide a packaging error, enable strict identity validation:

await fastify.register(versionify, {
    requireIdentity: true,
});

With requireIdentity: true, package loading or JSON parsing failures reject registration with ERR_VERSIONIFY_IDENTITY_LOAD, and missing, empty, or whitespace-only name or version values are rejected. The default remains compatible: an unreadable project package falls back to unknown and 0.0.0.

Route-level authentication and documentation can be attached without wrapping the plugin:

await fastify.register(versionify, {
    routeOptions: {
        schema: {
            tags: ["operations"],
            summary: "Application version",
        },
        config: { permission: "version:read" },
        logLevel: "warn",
        onRequest: async (request, reply) => {
            if (!request.user?.permissions.includes("version:read")) {
                await reply.code(403).send({ error: "Forbidden" });
            }
        },
    },
});

The route surface is explicitly limited to schema, config, logLevel, onRequest, preValidation, and preHandler; each hook accepts one function or an array of functions. Unknown options fail registration. method, url, and handler are reserved so the plugin always owns its GET/automatic HEAD contract, negotiated response, and endpoint path.

Example with Metadata and Cache Control

import process from "node:process";
import versionify from "@ynode/versionify";

await fastify.register(versionify, {
    metadata: { environment: "production", nodeVersion: process.version },
    build: { commit: process.env.GIT_SHA, time: process.env.BUILD_TIME },
    cacheMaxAge: 7200,
});

The JSON response will include all metadata fields alongside name and version:

{
    "name": "my-app",
    "version": "2.1.0",
    "environment": "production",
    "nodeVersion": "v22.0.0",
    "build": {
        "commit": "abc123",
        "time": "2026-07-21T12:34:56.000Z"
    }
}

Clients can reuse the response ETag in If-None-Match; when the version payload has not changed, the endpoint returns 304 Not Modified.

License

This project is licensed under the MIT License.