Current version: 1.4.13
Change log

Need a simple and lightweight logging for quick debugging? Try log4javascript Lite.

log4javascript is a JavaScript logging framework based on the Java logging framework log4j.

log4javascript 1.4.13 released

log4javascript 1.4.13 is now available. This is a minor release that fixes an issue with BrowserConsoleAppender introduced in version 1.4.12.

Start logging straight away

It takes one <script> include tag and one line of JavaScript to start using log4javascript. See the quick start tutorial to get started straight away, or have a look at the basic demo page to see it in action now.

Cross-browser JavaScript logging

log4javascript is designed to work in all major browsers. Internet Explorer 5 onwards on Windows, Firefox 1.0 onwards, Safari 1.2 onwards, Opera 8.01 onwards, Konqueror 3.4 onwards and Google Chrome are all fully supported.

Flexible logging

The default way to display log messages is in a separate log4javascript window, featuring advanced search and filtering functionality, as well as a command line. You can also log to an in-page log4javascript console, to Firebug, to Opera and Safari's built-in error consoles or back to the server via Ajax.

Familiar API

log4javascript's API is heavily based on log4j. log4j's API has been ported to many other languages so will be familiar to a large number of developers. log4javascript implements the key log4j concepts of loggers, appenders, layouts and levels.

Rigorously tested

log4javascript is extensively tested and comes with its own test runner and suite of unit tests.


log4javascript is licenced under the Apache License, Version 2.0.