Pretty printing in development

createLogger writes newline-delimited JSON, which is what you want in production and not what you want in a terminal. pino-pretty reformats it.

pnpm add -D pino-pretty

Option 1: pipe (recommended)

Piping keeps formatting out of your process entirely — no extra dependency at runtime, no worker thread, no risk of shipping the pretty printer to production.

{
	"scripts": {
		"dev": "node --experimental-strip-types src/main.ts | pino-pretty --colorize --translateTime SYS:HH:MM:ss.l --ignore pid,hostname"
	}
}

Output:

[14:22:31.004] INFO (tevm-node): forked mainnet
    chainId: 1
    blockNumber: "21000000"

Option 2: in-process transport

If you cannot control how the process is launched, configure the transport yourself. createLogger does not accept transport options, so build the pino instance directly for the dev path and keep createLogger for everything else:

import { createLogger, type Level, type Logger } from '@tevm/logger'
import { pino } from 'pino'
 
const level: Level = (process.env['LOG_LEVEL'] as Level | undefined) ?? 'info'
const isDev = process.env['NODE_ENV'] !== 'production'
 
/**
 * The application logger: pretty in development, JSON everywhere else.
 * @throws {Error} If `pino-pretty` is not installed while running in development.
 */
export const logger: Logger = isDev
	? (pino({
			name: 'tevm-app',
			level,
			transport: {
				target: 'pino-pretty',
				options: { colorize: true, translateTime: 'SYS:HH:MM:ss.l', ignore: 'pid,hostname' },
			},
		}) as Logger)
	: createLogger({ name: 'tevm-app', level })
 
logger.info('logger ready')

pino resolves target: 'pino-pretty' at construction time and throws if the module is not installed — hence the @throws above. Keep pino-pretty in devDependencies and make sure NODE_ENV=production is actually set in production, or the process will fail to start.

Browser bundles

Transports are a Node feature (they run in a worker thread). Never let the branch above reach a browser bundle — pino-pretty pulls in node:worker_threads and will break the build. If the same module is shared between server and browser code, guard on the runtime instead of the environment variable:

import { createLogger, type Logger } from '@tevm/logger'
 
const isBrowser = typeof window !== 'undefined'
 
export const logger: Logger = createLogger({
	name: isBrowser ? 'tevm-web' : 'tevm-server',
	level: isBrowser ? 'warn' : 'info',
})

In the browser, pino writes through console.info/console.warn/console.error, which DevTools already formats — no pretty printer needed.