🌲 super fast, all natural json logger 🌲
JavaScript HTML
Clone or download
Latest commit e7c9c0c Jun 13, 2018



pino  Build Status Coverage Status TypeScript definitions on DefinitelyTyped

Extremely fast node.js logger, inspired by Bunyan. It also includes a shell utility to pretty-print its log files.



npm install pino --save

If you need support for Node.js v0.12 or v0.10, please install the latest 2.x release using the legacy tag:

npm install pino@legacy --save

Documentation for the legacy version 2.x is available on the v2.x.x branch.


'use strict'

var pino = require('pino')()

pino.info('hello world')
pino.error('this is at error level')
pino.info('the answer is %d', 42)
pino.info({ obj: 42 }, 'hello world')
pino.info({ obj: 42, b: 2 }, 'hello world')
pino.info({ obj: { aa: 'bbb' } }, 'another')
setImmediate(function () {
  pino.info('after setImmediate')
pino.error(new Error('an error'))

var child = pino.child({ a: 'property' })
child.info('hello child!')

var childsChild = child.child({ another: 'property' })
childsChild.info('hello baby..')

This produces:

{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"hello world","time":1459529098958,"v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":50,"msg":"this is at error level","time":1459529098959,"v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"the answer is 42","time":1459529098960,"v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"hello world","time":1459529098960,"obj":42,"v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"hello world","time":1459529098960,"obj":42,"b":2,"v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":50,"msg":"an error","time":1459529098961,"type":"Error","stack":"Error: an error\n    at Object.<anonymous> (/Users/davidclements/z/nearForm/pino/example.js:14:12)\n    at Module._compile (module.js:435:26)\n    at Object.Module._extensions..js (module.js:442:10)\n    at Module.load (module.js:356:32)\n    at Function.Module._load (module.js:311:12)\n    at Function.Module.runMain (module.js:467:10)\n    at startup (node.js:136:18)\n    at node.js:963:3","v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"hello child!","time":1459529098962,"a":"property","v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"hello baby..","time":1459529098962,"another":"property","a":"property","v":1}
{"pid":94473,"hostname":"MacBook-Pro-3.home","level":30,"msg":"after setImmediate","time":1459529098963,"v":1}


As far as we know, it is one of the fastest loggers in town:

pino.info('hello world'):

BASIC benchmark averages
Bunyan average: 549.042ms
Winston average: 467.873ms
Bole average: 201.529ms
Debug average: 253.724ms
LogLevel average: 282.653ms
Pino average: 188.956ms
PinoExtreme average: 108.809ms

pino.info({'hello': 'world'}):

OBJECT benchmark averages
BunyanObj average: 564.363ms
WinstonObj average: 464.824ms
BoleObj average: 230.220ms
LogLevelObject average: 474.857ms
PinoObj average: 201.442ms
PinoUnsafeObj average: 202.687ms
PinoExtremeObj average: 108.689ms
PinoUnsafeExtremeObj average: 106.718ms


DEEPOBJECT benchmark averages
BunyanDeepObj average: 5293.279ms
WinstonDeepObj average: 9020.292ms
BoleDeepObj average: 9169.043ms
LogLevelDeepObj average: 15260.917ms
PinoDeepObj average: 8467.807ms
PinoUnsafeDeepObj average: 6159.227ms
PinoExtremeDeepObj average: 8354.557ms
PinoUnsafeExtremeDeepObj average: 6214.073ms

pino.info('hello %s %j %d', 'world', {obj: true}, 4, {another: 'obj'}):

BunyanInterpolateExtra average: 778.408ms
WinstonInterpolateExtra average: 627.956ms
BoleInterpolateExtra average: 429.757ms
PinoInterpolateExtra average: 316.043ms
PinoUnsafeInterpolateExtra average: 316.809ms
PinoExtremeInterpolateExtra average: 218.468ms
PinoUnsafeExtremeInterpolateExtra average: 215.040ms

In many cases, pino is over 5x faster than alternatives.

For a fair comparison, LogLevel was extended to include a timestamp and bole had fastTime mode switched on.


A transport in most logging libraries is something that runs in-process to perform some operation with the finalized log line. For example, a transport might send the log line to a standard syslog server after processing the log line and reformatting it. For details on implementing, and some already written, transports, see our Transports⇗ document.

Pino does not natively support in-process transports.

Pino does not support in-process transports because Node processes are single threaded processes (ignoring some technical details). Given this restriction, one of the methods Pino employs to achieve its speed is to purposefully offload the handling of logs, and their ultimate destination, to external processes so that the threading capabilities of the OS can be used (or other CPUs).

One consequence of this methodology is that "error" logs do not get written to stderr. However, since Pino logs are in a parseable format, it is possible to use tools like pino-tee or jq to work with the logs. For example, to view only logs marked as "error" logs:

$ node an-app.js | jq 'select(.level == 50)'

In short, the way Pino generates logs:

  1. Reduces the impact of logging on your application to an extremely minimal amount.
  2. Gives greater flexibility in how logs are processed and stored.

Given all of the above, Pino clearly promotes out-of-process log processing. However, it is possible to wrap Pino and perform processing in-process. For an example of this, see pino-multi-stream.

Pino in the browser

Pino is compatible with browserify for browser side usage:

This can be useful with isomorphic/universal JavaScript code.

By default, in the browser, pino uses corresponding Log4j console methods (console.error, console.warn, console.info, console.debug, console.trace) and uses console.error for any fatal level logs.

Browser Options

Pino can be passed a browser object in the options object, which can have the following properties:

asObject (Boolean)

var pino = require('pino')({browser: {asObject: true}})

The asObject option will create a pino-like log object instead of passing all arguments to a console method, for instance:

pino.info('hi') // creates and logs {msg: 'hi', level: 30, time: <ts>}

When write is set, asObject will always be true.

write (Function | Object)

Instead of passing log messages to console.log they can be passed to a supplied function.

If write is set to a single function, all logging objects are passed to this function.

var pino = require('pino')({browser: {write: (o) => {
  // do something with o

If write is an object, it can have methods that correspond to the levels. When a message is logged at a given level, the corresponding method is called. If a method isn't present, the logging falls back to using the console.

var pino = require('pino')({browser: {write: {
  info: function (o) {
    //process info log object
  error: function (o) {
    //process error log object

serialize: (Boolean | Array)

The serializers provided to pino are ignored by default in the browser, including the standard serializers provided with Pino. Since the default destination for log messages is the console, values such as Error objects are enhanced for inspection, which they otherwise wouldn't be if the Error serializer was enabled.

We can turn all serializers on,

var pino = require('pino')({
  browser: {
    serialize: true

Or we can selectively enable them via an array:

var pino = require('pino')({
  serializers: {
    custom: myCustomSerializer,
    another: anotherSerializer
  browser: {
    serialize: ['custom']
// following will apply myCustomSerializer to the custom property,
// but will not apply anotherSerizlier to another key
pino.info({custom: 'a', another: 'b'})  

When serialize is true the standard error serializer is also enabled (see https://github.com/pinojs/pino/blob/master/docs/API.md#stdSerializers). This is a global serializer which will apply to any Error objects passed to the logger methods.

If serialize is an array the standard error serializer is also automatically enabled, it can be explicitly disabled by including a string in the serialize array: !stdSerializers.err, like so:

var pino = require('pino')({
  serializers: {
    custom: myCustomSerializer,
    another: anotherSerializer
  browser: {
    serialize: ['!stdSerializers.err', 'custom'] //will not serialize Errors, will serialize `custom` keys

The serialize array also applies to any child logger serializers (see https://github.com/pinojs/pino/blob/master/docs/API.md#discussion-2 for how to set child-bound serializers).

Unlike server pino the serializers apply to every object passed to the logger method, if the asObject option is true, this results in the serializers applying to the first object (as in server pino).

For more info on serializers see https://github.com/pinojs/pino/blob/master/docs/API.md#parameters.

transmit (Object)

An object with send and level properties.

The transmit.level property specifies the minimum level (inclusive) of when the send function should be called, if not supplied the send function be called based on the main logging level (set via options.level, defaulting to info).

The transmit object must have a send function which will be called after writing the log message. The send function is passed the level of the log message and a logEvent object.

The logEvent object is a data structure representing a log message, it represents the arguments passed to a logger statement, the level at which they were logged and the heirarchy of child bindings.

The logEvent format is structured like so:

  ts = Number,
  messages = Array, 
  bindings = Array, 
  level: { label = String, value = Number}

The ts property is a unix epoch timestamp in milliseconds, the time is taken from the moment the logger method is called.

The messages array is all arguments passed to logger method, (for instance logger.info('a', 'b', 'c') would result in messages array ['a', 'b', 'c']).

The bindings array represents each child logger (if any), and the relevant bindings. For instance given logger.child({a: 1}).child({b: 2}).info({c: 3}), the bindings array would hold [{a: 1}, {b: 2}] and the messages array would be [{c: 3}]. The bindings are ordered according to their position in the child logger heirarchy, with the lowest index being the top of the heirarchy.

By default serializers are not applied to log output in the browser, but they will always be applied to messages and bindings in the logEvent object. This allows us to ensure a consistent format for all values between server and client.

The level holds the label (for instance info), and the corresponding numerical value (for instance 30). This could be important in cases where client side level values and labels differ from server side.

The point of the send function is to remotely record log messages:

var pino = require('pino')({
  browser: {
    transmit: {
      level: 'warn',
      send: function (level, logEvent) {
        if (level === 'warn') {
          // maybe send the logEvent to a separate endpoint
          // or maybe analyse the messages further before sending
        // we could also use the `logEvent.level.value` property to determine
        // numerical value
        if (logEvent.level.value >= 50) { // covers error and fatal

          // send the logEvent somewhere 


There's some fine points to be aware of, which are a result of worthwhile trade-offs:

11 Arguments

The logger functions (e.g. pino.info) can take a maximum of 11 arguments.

If you need more than that to write a log entry, you're probably doing it wrong.

Duplicate Keys

It's possible for naming conflicts to arise between child loggers and children of child loggers.

This isn't as bad as it sounds, even if you do use the same keys between parent and child loggers Pino resolves the conflict in the sanest way.

For example, consider the following:

var pino = require('pino')
var fs = require('fs')
  .child({a: 'property'})
  .child({a: 'prop'})
$ cat my-log

Notice how there's two key's named a in the JSON output. The sub-childs properties appear after the parent child properties. This means if we run our logs through pino -t (or convert them to objects in any other way) we'll end up with one a property whose value corresponds to the lowest child in the hierarchy:

$ cat my-log | pino -t

This equates to the same log output that Bunyan supplies.

One of Pino's performance tricks is to avoid building objects and stringifying them, so we're building strings instead. This is why duplicate keys between parents and children will end up in log output.

The Team

Matteo Collina




David Mark Clements




James Sumners




Thomas Watson Steen




Chat on Gitter


Chat on IRC

You'll find an active group of Pino users in the #pinojs channel on Freenode, including some of the contributors to this project.


Pino is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the CONTRIBUTING.md file for more details.


This project was kindly sponsored by nearForm.

Logo and identity designed by Cosmic Fox Design: https://www.behance.net/cosmicfox.


Licensed under MIT.