To capture a HAR file, navigate to the webpage where you saw the bug, open Developer Tools in your browser, switch to the Network tab, check "Preserve log", and click the red button to start recording. Recreate the bug and stop recording when done, then export the HAR file by clicking the down arrow button. Alternatively, use Jam, a free tool that automatically captures HAR file data with just three steps: installing the extension, choosing between screenshot or video capture, and clicking "Create" to generate a link to your bug report.