Record the smallest useful journey.
In Chrome, open Developer Tools and the Network panel. Clear unrelated traffic, reproduce the problem and export a HAR. Enable Preserve log if the relevant request would disappear during navigation.
Chrome offers sanitised export and an option to include sensitive data. Even a sanitised export needs review: stripping common authentication headers does not prove that URLs or bodies contain no personal data.
Reference: Chrome’s HAR export documentation.
Open the recording without replaying it.
Use the browser HAR viewer to open a file up to 20 MB. Filter by URL, status or method, sort by duration, and select a request to inspect headers, query parameters, captured bodies and timing phases. Processing stays in the tab; no recorded request is executed.
For larger recordings, narrow the reproduction or inspect the file locally with a suitable desktop tool. Avoid uploading a production recording to an unknown service.
Follow the task across responses.
Find the first user action, then the relevant API response and next request. A job-creation response followed by a 403 download points to a different failure from a 500 during generation.
Check 200 responses too. They may hold an HTML login page, an application-level rejection or a stale value. The recording is evidence of what was captured; it is not a complete account of server state.
Use JSON diff for two response payloads and the header parser for copied headers.
Try a successful export with a failed download.
Download this two-request recording and open it in the HAR viewer. The POST to /api/export returns 200 with ready: true. One second later, the GET for report.csv returns 403.
Select request #2. Its response body contains Access denied. The export request succeeded, but the recorded download did not. This alone cannot establish whether the denial came from an expired signature, missing permission or another access rule.
Use the signed-download checks to investigate expiry, or the cookie checks if the authorised session was missing. After fixing the cause, reproduce the same journey and inspect the downloaded file.