HTTP Archive Files (HARZ and HAR)

Created by Dan Auns, Modified on Tue, 29 Jan, 2019 at 5:32 PM by Dan Auns

When troubleshooting browser based software, often times it is necessary to inspect the interactions between the browser and the systems that serve up the experience. HTTP Archive format files, allow us to capture and inspect this network activity.

The term 'HAR File' is used generally when describing this sort of file, but their are important differences between HARZ and HAR files.

HARZ files are compressed, and can be generated with tools like the Google Tag Assistant. Troubleshooting pixel firing, is a typical use case for examining a HARZ file captured with a tool like GTA.

HAR files slightly different and contain more information, including network status codes. This information is needed as sometimes the network itself can cause issues with data transfer between the source and browser. Troubleshooting unpredictable error messages with server codes, starts by reviewing HAR filies and inspecting server response codes.

How to generate a HAR files using Chrome Developer Tools, built into the Chrome browser:

  • Open Google Analytics.
  • Press F12 in the browser to open the Developer Tools.
  • Within the Developer Tools panel, go to the "Network" tab.
  • Navigate to real-time reporting.
  • Several HTTP requests should show up in the network log. Look for ones that have a status other than 200. Especially interesting is anything 400+; these will usually be red. A 407 in particular is problematic.
  • Right-click on one of those requests (Or more if there are a variety of error codes) and click "Save as HAR with content."
  • Recommended: Also record a screenshot of the whole list of requests.


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