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How to Collect a HAR File and HTTP Error Logs Using Firefox

How to Collect a HAR File and HTTP Error Logs Using Firefox


  • Mozilla Firefox: All Supported Versions


Capture diagnostic logs from a web browser for UI troubleshooting using Firefox


  1. Press F12 to open the Debug pane.
  2. Navigate to the Network tab.
  3. Click on the User-added image button to start recording.
  4. Reproduce the action in question.
  5. Right click on the recorded events > Save All as HAR
  6. Check for and save HTTP Error details
    1. For any errors observed above, note the Request URL and HTTP error number (4## or 5##)
    2. Select the Console tab
    3. Locate the error number tied to the Request URL
    4. Right-click matching error and click "Save As..."
    5. Set name of file, including at least HTTP error number, and save file to your computer
      Original filename: defense-prod05.conferdeploy.net-1646930859819.log
      Updated filename: 400_defense-prod05.conferdeploy.net-1646930859819.log
  7. Attach the HAR file and HTTP Error file to the case, or use CB Vault if the file is larger than 25 MB

Additional Notes

  • To stop recording click on the trashcan at the top left of the Debug pane.
  • If a graph appears instead of the events click the Back button on the left side of the Debug pane.
  • HAR Files under 25 MB can be attached directly to a Carbon Black Technical Support case. 
  • Files larger than 25 MB should be uploaded to CB Vault.

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