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


Article ID: 286830


Updated On:


Carbon Black App Control (formerly Cb Protection) Carbon Black Cloud Endpoint Standard (formerly Cb Defense) Carbon Black Cloud Enterprise EDR (formerly Cb Threathunter) Carbon Black EDR (formerly Cb Response)


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


  • Mozilla Firefox: All Supported Versions


  1. Press F12 to open the Debug pane.
  2. Navigate to the Network tab.
  3. Recording should start automatically or Click on the Pause/Resume Recording 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:
      Updated filename:
  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 Information

  • 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.
  • All credentials and session cookies within a HAR file should be removed before sharing with Carbon Black
    • The HAR file is a text file, it can be opened in a text editor and searched for the SESSION cookie value and replaced with <REDACTED>
    • This can also be done for passwords and API tokens if they were part of the recording
    • It's also recommended to logout from the Carbon Black session after recording a HAR session. This is a precaution that should invalidate session IDs if any were missed.
  • 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.