Fastify deploys, but the app is unreachable

If the build passes and the URL still fails, Fastify is either not listening where the platform expects or it crashed while starting.

Last updated November 9, 2026

Check the logs

npx ezhst logs --tail 200

An exception here means the app crashed at boot. A missing variable is a common reason.

Check host and port

Fastify listens on 127.0.0.1 unless told otherwise. Call app.listen({ port: Number(process.env.PORT), host: "0.0.0.0" }).

src/index.ts

import Fastify from "fastify";

const app = Fastify({ logger: true });

app.get("/", async () => {
  return { hello: "EasyHost" };
});

await app.listen({ port: Number(process.env.PORT), host: "0.0.0.0" });

Check the start command

Fastify starts with scripts.start, then main, index.js or server.js.

npx ezhst build show

Known cause for Fastify

Forgetting host is the most common Fastify deploy failure: the build succeeds, but the app never receives traffic.

See the Fastify hub for every Fastify guide, or free Fastify hosting for what is included.

Start for free

Install the skill, choose Global or Local, then tell your agent to deploy. No credit card, no config files.

npx ezhst skill install