"Google Analytics Tracking Code Debugger is a new debug version of Analytics Tracking code called ga_debug.js to verify your tracking code setup. Also released a Chrome extension which uses ga_debug.js script, allowing you to use new ga_debug.js without re-tagagging any of your content. You can also use this extension to verify what information is sent to Analytics with each page," informs Google.
For using ga_debug.js without Chrome extension, read Troubleshooting Guide. Note: This script is meant for debugging and analysis only, thus it should only be used on testing environment. To learn about the kinds of errors this script can find, see Common Tracking Code Errors/Typos.