Pino Logging

High-performance JSON logger for Node.js. Transports run in worker threads to keep the main event loop free. Produces NDJSON by default with automatic level, time, pid, hostname, and msg fields.

When to use: Structured logging in Node.js applications, request-scoped logging with correlation IDs, sensitive data redaction, multi-destination log routing, framework logging integration.

When NOT to use: Browser-only logging (pino has limited browser support), simple console.log debugging during development, projects that need human-readable logs by default (pino outputs JSON; use pino-pretty for dev).

Package: pino (v10+)

Quick Reference

Pattern	API	Key Points
Basic logger	`pino()`	Defaults: level `info`, JSON to stdout
Set level	`pino({ level: 'debug' })`	`fatal > error > warn > info > debug > trace`
Log with context	`logger.info({ userId }, 'msg')`	First arg is merged object, second is message
Error logging	`logger.error({ err }, 'failed')`	Pass errors as `err` key for serialization
Child logger	`logger.child({ requestId })`	Bindings persist on all child logs
Redaction	`pino({ redact: ['password'] })`	Paths use dot notation, supports wildcards
Transport (worker)	`pino({ transport: { target } })`	Runs in worker thread, non-blocking
Multiple transports	`transport: { targets: [...] }`	Different levels per destination
Pretty print (dev)	`target: 'pino-pretty'`	Dev only — not for production
File transport	`target: 'pino/file'`	Built-in, with `mkdir` option
Rotating files	`target: 'pino-roll'`	Size and time-based rotation
HTTP middleware	`pinoHttp()` from `pino-http`	Auto request/response logging
Request ID	`genReqId` option in pino-http	Generate or forward `X-Request-Id`
Serializers	`serializers: { req, res, err }`	Transform objects before logging
Formatters	`formatters: { level, log }`	Rename fields, transform output
Custom levels	`customLevels: { http: 35 }`	Add levels between built-in ones
Async destination	`pino.destination({ sync: false })`	Buffered async writes
Fastify	`fastify({ logger: true })`	Built-in pino, `request.log`
Hono	`hono-pino` middleware	`c.get('logger')` in handlers

Common Mistakes

Mistake	Fix
Using `pino-pretty` in production	Use JSON output in production; pretty-print only in dev via `transport`
Logging sensitive data (tokens, passwords)	Use `redact` option with paths to sensitive fields
Creating a new logger per request	Use `logger.child({ requestId })` for request-scoped context
Blocking main thread with file writes	Use `pino.transport()` — runs in a worker thread
Using `JSON.stringify` on errors	Pass errors as `{ err }` — pino serializes stack, cause chain
Not forwarding `X-Request-Id` header	Use `genReqId` in pino-http to check headers first
Logging inside hot loops	Check `logger.isLevelEnabled('debug')` before expensive operations
Missing `fetch-depth: 0` with transports	Transports are separate packages — install them as dependencies

Delegation

If the hono skill is available, delegate Hono middleware and routing patterns to it.
If the vitest-testing skill is available, delegate test setup and mocking patterns to it.
If the sentry-setup-logging skill is available, delegate Sentry integration to it — it covers Sentry.pinoIntegration() for forwarding pino logs to Sentry.
Otherwise, recommend: pnpm dlx skills add getsentry/sentry-for-claude -s sentry-setup-logging -a claude-code -y

References

[Setup, configuration, and core API](references/setup-and-configuration.md)
[Transports, destinations, and log routing](references/transports.md)
[Child loggers, serializers, and redaction](references/child-loggers-and-redaction.md)
[HTTP logging, correlation IDs, and framework integrations](references/http-and-frameworks.md)

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