`reply.sent`

A boolean indicating whether the response has already been sent.

Since Fastify 5 Spec ↗

Syntax

reply.sent

Returns

boolean — true once the response has been dispatched.

Examples

import Fastify from 'fastify';

const app = Fastify();

app.get('/race', async (_req, reply) => {
  const timeout = setTimeout(() => {
    if (!reply.sent) reply.code(504).send({ error: 'timeout' });
  }, 5000);
  try {
    return await slowWork();
  } finally {
    clearTimeout(timeout);
  }
});

Notes

Check reply.sent before sending again to avoid "reply already sent" errors in race conditions such as timeouts. In modern Fastify prefer returning values; sent is mainly for guarding manual send paths.