Diagnosis, exercises and capstone
Diagnosing with DevTools, curl and HAR
Read request evidence instead of guessing.
Understand the concept
Inspect URL, method, status, initiator, fields, payload and timing together. Preserve log helps with navigation chains. Disabling browser cache does not purge CDN or service-worker state.
Copied curl commands and HAR exports can contain tokens, cookies and personal data; redact before sharing. Browser-only failures may involve CORS or cookie policy, but compare requests before concluding.
Check origin, credentials, method, media type and proxy path. Sanitised correlation IDs and timestamps help locate server evidence. Practise only against systems you own or are authorised to test.
Produce reproducible bug reports rather than vague symptoms.
Uploading an unredacted HAR to GitHub.
One topic. Three levels of depth.
curl.exe -I https://example.comUses HEAD to inspect response fields.
This page does not send requests to external servers. Messages are readable HTTP/1.1 illustrations, not HTTP/2 or HTTP/3 wire dumps. example.test is reserved for examples. Run commands and JavaScript only in your own test environment; never publish real tokens or cookies.
Try it yourself first.
Should you share Copy as curl output directly?
Show the solution and explanation
Redact credentials, cookies and personal data firstNo; redact sensitive fields first.