Implementation:Promptfoo Promptfoo Logger Browser

Knowledge Sources	Promptfoo_Promptfoo
Domains	Logging, Browser
Last Updated	2026-02-14 07:45 GMT

Overview

Lightweight browser-compatible logger that mirrors the Node.js logger API surface, used in web UI builds via Vite aliasing.

Description

The Logger_Browser module (logger.browser.ts) provides a minimal console-based logging implementation that matches the same API as the full Winston-based Node logger. It supports four log levels (error, warn, info, debug), basic sensitive field sanitization (redacting keys, secrets, tokens, passwords), and no-op stubs for Node-specific features (transports, file logging, source maps). Vite aliases this module in place of ./logger for browser builds.

Usage

This module is not imported directly. It is aliased by Vite when building the browser (web UI) bundle, replacing ./logger to avoid Node.js dependencies.

Code Reference

Source Location

• Repository: Promptfoo_Promptfoo
• File: src/logger.browser.ts
• Lines: 1-126

Signature

export const LOG_LEVELS = { error: 0, warn: 1, info: 2, debug: 3 } as const;
export function getLogLevel(): LogLevel
export function setLogLevel(level: LogLevel): void
export function isDebugEnabled(): boolean
export function setLogCallback(cb: ((msg: string) => void) | null): void

declare const logger: {
  error: (msg: string, ctx?: Record<string, unknown>) => void;
  warn: (msg: string, ctx?: Record<string, unknown>) => void;
  info: (msg: string, ctx?: Record<string, unknown>) => void;
  debug: (msg: string, ctx?: Record<string, unknown>) => void;
  level: string;
};
export default logger;

Import

// Aliased automatically by Vite; not imported directly
import logger from './logger'; // resolves to logger.browser.ts in browser builds

I/O Contract

Inputs

Name	Type	Required	Description
message	string	Yes	Log message
context	Record<string, unknown>	No	Context object (sensitive fields auto-redacted)

Outputs

Name	Type	Description
console output	void	Messages written to browser console

Usage Examples

import logger from './logger'; // Resolves to browser logger in web UI

logger.info('Page loaded');
logger.debug('API response', { data: response, apiKey: 'sk-secret' });
// apiKey will be redacted to '[REDACTED]'

Related Pages

• Environment:Promptfoo_Promptfoo_Browser_Automation