These docs are for v2020.1. Click to read the latest docs for v2024.3.


Node.js apps can log to Seq with the Bunyan logging framework

The Bunyan library is a logger for JavaScript with wide platform support and good facilities for structured log messages. The bunyan-seq package is a plug-in for Bunyan that batches log events and posts the to the Seq HTTP ingestion API.


More Seq options for Node.js

See also pino-seq for the pino logging library, and winston-seq for Winston.

Getting started

First, install both the bunyan and bunyan-seq packages.

npm install --save bunyan
npm install --save bunyan-seq

When configuring the Bunyan logger, pass a Seq stream using createStream():

let bunyan = require('bunyan');
let seq = require('bunyan-seq');

var log = bunyan.createLogger({
    name: 'myapp',
    streams: [
            stream: process.stdout,
            level: 'warn',
            serverUrl: 'http://localhost:5341',
            level: 'info'
log.warn({lang: 'fr'}, 'Au revoir');


The createStream() method accepts a configuration object with the following parameters. No parameters are required.

apiKeyThe API Key to use when connecting to Seq
batchSizeLimit1048576 (1 MiB)The maximum batch size to send to Seq (should not exceed Settings > System > Raw ingestion payload limit)
eventSizeLimit262144 (256 kiB)The maximum event size to send to Seq; larger events will be dumped to stdout (should match Settings > System > Raw event body limit)
levelThe Bunyan logging level for the stream
maxBatchingTime2000The time in milliseconds that the logger will wait for additional events before sending a batch to Seq
nameThe Bunyan stream name, which can be used when configuring Bunyan filters
onErrorLog to consoleA function to receive any errors raised when sending events to Seq
reemitErrorEventsfalseIf true, error events raised by the stream will propagate as 'error' events on the Bunyan logger object.
serverUrlhttp://localhost:5341The HTTP endpoint address of the Seq server

Message templates

You can specify property names as tokens in the log message to control how the event is rendered in Seq:{user: 'Alice'}, 'Hi, {user}!');

It is not necessary to specify tokens for all properties, but using this technique instead of string formatting will produce more easily machine-readable log events by associating the same template, and thus the same event id, with related events.