This module provides a basic ndjson formatter. If an incoming line looks like it could be a log line from an ndjson logger, in particular the Pino logging library, then it will apply extra formatting by considering things like the log level and timestamp.

A standard Pino log line like:

{"level":30,"time":1522431328992,"msg":"hello world","pid":42,"hostname":"foo","v":1}

Will format to:

[1522431328992] INFO (42 on foo): hello world

If you landed on this page due to the deprecation of the prettyPrint option of pino, read the Programmatic Integration section.

Using the example script from the Pino module, and specifying that logs should be colored and the time translated, we can see what the prettified logs will look like:

$ npm install -g pino-pretty

It is recommended to use pino-pretty with pino by piping output to the CLI tool:

node app.js | pino-pretty

• --colorize (-c): Adds terminal color escape sequences to the output.
• --crlf (-f): Appends carriage return and line feed, instead of just a line feed, to the formatted log line.
• --errorProps (-e): When formatting an error object, display this list of properties. The list should be a comma-separated list of properties Default: ''. Do not use this option if logging from pino@7. Support will be removed from future verions.
• --levelFirst (-l): Display the log level name before the logged date and time.
• --errorLikeObjectKeys (-k): Define the log keys that are associated with error like objects. Default: err,error.
• --messageKey (-m): Define the key that contains the main log message. Default: msg.
• --levelKey (--levelKey): Define the key that contains the level of the log. Default: level.
• --levelLabel (-b): Output the log level using the specified label. Default: levelLabel.
• --minimumLevel (-L): Hide messages below the specified log level. Accepts a number, trace, debug, info, warn, error, or fatal. If any more filtering is required, consider using jq.
• --customLevels (-x): Override default levels with custom levels, e.g. -x err:99,info:1
• --customColors (-X): Override default colors with custom colors, e.g. -X err:red,info:blue
• --useOnlyCustomProps (-U): Only use custom levels and colors (if provided) (default: true); else fallback to default levels and colors, e.g. -U false
• --messageFormat (-o): Format output of message, e.g. {levelLabel} - {pid} - url:{request.url} will output message: INFO - 1123 - url:localhost:3000/test Default: false
• --timestampKey (-a): Define the key that contains the log timestamp. Default: time.
• --translateTime (-t): Translate the epoch time value into a human-readable date and time string. This flag also can set the format string to apply when translating the date to a human-readable format. For a list of available pattern letters, see the dateformat documentation.
  • The default format is yyyy-mm-dd HH:MM:ss.l o in UTC.
  • Require a SYS: prefix to translate time to the local system's time zone. A shortcut SYS:standard to translate time to yyyy-mm-dd HH:MM:ss.l o in system time zone.
• --ignore (-i): Ignore one or several keys, nested keys are supported with each property delimited by a dot character (.), keys may be escaped to target property names that contains the delimiter itself: (-i time,hostname,req.headers,log\\.domain\\.corp/foo)
• --hideObject (-H): Hide objects from output (but not error object)
• --singleLine (-S): Print each log message on a single line (errors will still be multi-line)
• --config: Specify a path to a config file containing the pino-pretty options. pino-pretty will attempt to read from a .pino-prettyrc in your current directory (process.cwd) if not specified

We recommend against using pino-pretty in production and highly recommend installing pino-pretty as a development dependency.

Install pino-pretty alongside pino and set the transport target to 'pino-pretty':

const pino = require('pino')
const logger = pino({
  transport: {
    target: 'pino-pretty'
  },
})

logger.info('hi')

The transport option can also have an options object containing pino-pretty options:

const pino = require('pino')
const logger = pino({
  transport: {
    target: 'pino-pretty',
    options: {
      colorize: true
    }
  }
})

logger.info('hi')

Use it as a stream:

const pino = require('pino')
const pretty = require('pino-pretty')
const logger = pino(pretty())

logger.info('hi')

Options are also supported:

const pino = require('pino')
const pretty = require('pino-pretty')
const stream = pretty({
  colorize: true
})
const logger = pino(stream)

logger.info('hi')

See the Options section for all possible options.

If you are using pino-pretty as a stream and you need to provide options to pino, pass the options as the first argument and pino-pretty as second argument:

const pino = require('pino')
const pretty = require('pino-pretty')
const stream = pretty({
  colorize: true
})
const logger = pino({ level: 'info' }, stream)

// Nothing is printed
logger.debug('hi')

Logging with Jest is problematic, as the test framework requires no asynchronous operation to continue after the test has finished. The following is the only supported way to use this module with Jest:

import pino from 'pino'
import pretty from 'pino-pretty'

test('test pino-pretty', () => {
  const logger = pino(pretty({ sync: true }));
  logger.info('Info');
  logger.error('Error');
});

Using the new pino v7+ transports not all options are serializable, for example if you want to use messageFormat as a function you will need to wrap pino-pretty in a custom module.

Executing main.js below will log a colorized hello world message using a custom function messageFormat:

// main.js
const pino = require('pino')

const logger = pino({
  transport: {
    target: './pino-pretty-transport',
    options: {
      colorize: true
    }
  },
})

logger.info('world')

// pino-pretty-transport.js
module.exports = opts => require('pino-pretty')({
  ...opts,
  messageFormat: (log, messageKey) => `hello ${log[messageKey]}`
})

The options accepted have keys corresponding to the options described in CLI Arguments:

{
  colorize: colorette.isColorSupported, // --colorize
  crlf: false, // --crlf
  errorLikeObjectKeys: ['err', 'error'], // --errorLikeObjectKeys
  errorProps: '', // --errorProps
  levelFirst: false, // --levelFirst
  messageKey: 'msg', // --messageKey
  levelKey: 'level', // --levelKey
  messageFormat: false, // --messageFormat
  timestampKey: 'time', // --timestampKey
  translateTime: false, // --translateTime
  ignore: 'pid,hostname', // --ignore
  hideObject: false, // --hideObject
  singleLine: false, // --singleLine

  // The file or file descriptor (1 is stdout) to write to
  destination: 1,

  // Alternatively, pass a `sonic-boom` instance (allowing more flexibility):
  // destination: new SonicBoom({ dest: 'a/file', mkdir: true })

  // You can also configure some SonicBoom options directly
  sync: false, // by default we write asynchronously
  append: true, // the file is opened with the 'a' flag
  mkdir: true, // create the target destination


  customPrettifiers: {}
}

The colorize default follows colorette.isColorSupported.

The defaults for sync, append, mkdir inherit from SonicBoom(opts).

customPrettifiers option provides the ability to add a custom prettify function for specific log properties. customPrettifiers is an object, where keys are log properties that will be prettified and value is the prettify function itself. For example, if a log line contains a query property, you can specify a prettifier for it:

{
  customPrettifiers: {
    query: prettifyQuery
  }
}
//...
const prettifyQuery = value => {
  // do some prettify magic
}

Additionally, customPrettifiers can be used to format the time, hostname, pid, name, caller and level outputs:

{
  customPrettifiers: {
    // The argument for this function will be the same
    // string that's at the start of the log-line by default:
    time: timestamp => `🕰 ${timestamp}`,

    // The argument for the level-prettifier may vary depending
    // on if the levelKey option is used or not.
    // By default this will be the same numerics as the Pino default:
    level: logLevel => `LEVEL: ${logLevel}`

    // other prettifiers can be used for the other keys if needed, for example
    hostname: hostname => colorGreen(hostname)
    pid: pid => colorRed(hostname)
    name: name => colorBlue(name)
    caller: caller => colorCyan(caller)
  }
}

Note that prettifiers do not include any coloring, if the stock coloring on level is desired, it can be accomplished using the following:

const { colorizerFactory } = require('pino-pretty')
const levelColorize = colorizerFactory(true)
const levelPrettifier = logLevel => `LEVEL: ${levelColorize(logLevel)}`
//...
{
  customPrettifiers: { level: levelPrettifier }
}

messageFormat option allows you to customize the message output. A template string like this can define the format:

{
  messageFormat: '{levelLabel} - {pid} - url:{request.url}'
}

This option can also be defined as a function with this prototype:

{
  messageFormat: (log, messageKey, levelLabel) => {
    // do some log message customization
    return customized_message;
  }
}

Because pino-pretty uses stdout redirection, in some cases the command may terminate with an error due to shell limitations.

For example, currently, mingw64 based shells (e.g. Bash as supplied by git for Windows) are affected and terminate the process with a stdout is not a tty error message.

Any PRs are welcomed!

MIT License