HTTP headers
Access-Control-Request-Headers HTTP Header Meaning
Access-Control-Request-Headers lists headers a CORS preflight wants to send.
Meaning
The browser is asking whether a future cross-origin request may include these request headers.
Where it appears
Browsers send it on preflight OPTIONS requests when custom or non-simple headers are involved.
What to check
Check the matching Access-Control-Allow-Headers response and case-insensitive header names.
Example
Access-Control-Request-Headers: content-type, authorization