What is an HAR file
The HAR file is a file format used by several HTTP session tools to export the captured data. The format is basically a JSON object with a particular field distribution. You can find more information here.
How to record an HAR file
Google Chrome
Right click anywhere on the page, and then choose Inspect Element.
Select the Network tab.
Check if there is a little round red button on the top left of the Newtork tab. If there is, that means that the HAR file is already being recorded.
Refresh the page and navigate as you usually do. This is the step where you’ll be reproducing the problem you are having so it gets recorded in the HAR file. Note: Do not open a new tab, as you are only recording the tab where you opened the Network tab.
Once you completed all the steps and reproduced the error, right click inside the panel.
Click on Save all as HAR with Content.
A Save As dialog will open. Save the HAR file to your computer.
And you’re done. Now you can get that file and attach it to the support ticket.
https://connect.careerbuilder.com/s/article/How-to-create-a-HAR-file-within-Chrome - acho que podemos ou tirar prints daqui, ou tirar uns semelhantes 
Other supported browsers
If you are using a different browser like firefox or Edge, you can follow this guide on how to record a HAR file.