Relay for Node

API testing on your backend's existing /relay route. The UI, themes and assets are bundled. No Python, repository clone, frontend build or CDN is required.

npm install relay-backend

Express

import express from 'express';
import { relay } from 'relay-backend';
import { openapi } from './generated-openapi.js';

const app = express();
const tester = relay({ openapi, enabled: process.env.NODE_ENV !== 'production' });
app.use(tester); // Before body parsers and catch-all handlers.
app.use(express.json());
// Register your API routes as usual.
const server = app.listen(3000);
server.on('close', () => void tester.close());

Open http://localhost:3000/relay. If your backend already serves /openapi.json, omit openapi. A provider such as openapi: () => generatedDocument supports regenerated schemas.

Fastify

import Fastify from 'fastify';
import swagger from '@fastify/swagger';
import { relayFastify } from 'relay-backend';

const app = Fastify();
await app.register(swagger, {
  openapi: { info: { title: 'My Portal', version: '1' } }
});
// Register your API routes with their schemas here.
await app.register(relayFastify, {
  enabled: process.env.NODE_ENV !== 'production'
});
await app.listen({ port: 3000 });

Fastify reads app.swagger() automatically. With another generator, pass its document using openapi. Application hooks still apply, so configure your authentication hooks to allow the local /relay tooling routes if they otherwise protect every path.

JavaScript and TypeScript

ES modules and CommonJS are supported, with bundled TypeScript declarations:

const { relay, relayFastify } = require('relay-backend');

Node 22.13 or newer is required. Express, Fastify and Node HTTP are the tested adapters. Route definitions and request schemas come from OpenAPI 3.0/3.1 JSON; Relay cannot infer TypeScript interfaces or undocumented Express routes. Other frameworks and runtimes need their own adapter verification.

Standalone

For a local backend that already exposes OpenAPI:

npx relay-backend --target http://127.0.0.1:3000

This opens a separate tester at http://127.0.0.1:4477/relay/. Native mounting uses the backend's existing port instead. A saved report opens with npx relay-backend open endpoint.relay.

Team statuses

Endpoints start as Done. Status changes are manual. Set syncStatus: true to share them automatically through your existing Git origin using a separate relay-status branch. Git identity attributes each status update; native Node handler authors are not currently inferred. Request bodies, tokens and responses are never stored in that branch. Keep Git credentials configured on each developer's machine. See the team guide.

Relay accepts loopback hosts and clients only and requires same-origin CSRF protection for tester actions. API execution runs real backend handlers. Multipart uploads, external/YAML references, browser OAuth and public hosting are outside this version's scope.

Detailed configuration: Node integration guide. Apache-2.0; bundled third-party licenses are included.