PostHog Transport Browser Server

posthog-js is PostHog's official JavaScript logging SDK.

Transport Source

Installation

Install the required packages:

npm

npm i loglayer @loglayer/transport-posthog posthog-js serialize-error

pnpm

pnpm add loglayer @loglayer/transport-posthog posthog-js serialize-error

yarn

yarn add loglayer @loglayer/transport-posthog posthog-js serialize-error

Cross-Engine Compatibility

The posthog-js SDK works in both Node.js and browser environments. It may also work in Deno and Bun, but this has not been tested.

Setup

import { posthog } from 'posthog-js'
import { serializeError } from 'serialize-error'
import { LogLayer } from 'loglayer'
import { PosthogTransport } from "@loglayer/transport-posthog"

// Initialize PostHog with logs configuration
posthog.init('<ph_project_token>', {
  api_host: 'https://us.i.posthog.com',
  defaults: '2026-01-30',
  logs: {
    serviceName: 'my-app',
    environment: 'production',
  },
})

const log = new LogLayer({
  transport: new PosthogTransport({
    logger: posthog,
  }),
  errorSerializer: serializeError,
})

log.info('hello from LogLayer')
log.withMetadata({ order_id: 'ord_123' }).info('checkout completed')

Configuration Options

Required Parameters

Name	Type	Description
logger	PostHog	The initialized PostHog client instance

Optional Parameters

Name	Type	Default	Description
enabled	boolean	true	Whether the transport is enabled
level	"trace" | "debug" | "info" | "warn" | "error" | "fatal"	"trace"	Minimum log level to process. Logs below this level will be filtered out

Log Level Mapping

LogLayer	PostHog
trace	trace
debug	debug
info	info
warn	warn
error	error
fatal	fatal

Changelog

View the changelog here.