Try HTTP requests from your browser. Cross-origin responses require the target server to allow CORS.
Browser limits. There is no server proxy: requests use your browser’s fetch rules.
Cross-origin APIs must send CORS headers; you cannot set forbidden headers (e.g. Cookie) from arbitrary origins, and fetch does not impersonate logged-in Chrome sessions elsewhere.
This page sends default credentials (omit / same-origin only); OAuth cookies on third-party origins are intentionally out of scope.
HTTPS pages cannot call plain http:// (mixed content). “Failed to fetch” is usually CORS, TLS, DNS, or network—not a defect in this page.
Compare with curl builder or paste the generated shell line from Copy as cURL below (works from filled fields—even before Send).
Large JSON bodies paste cleanly through JSON Formatter via the response handoff (?in= base64url UTF-8; capped in this desk).
Runs locally · no proxy · failures may be network or CORS