Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed

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Reason

Reason: Multiple CORS header 'Access-Control-Allow-Origin' not allowed

What went wrong?

More than one {{HTTPHeader("Access-Control-Allow-Origin")}}  header was sent by the server. This isn’t allowed.

If you have access to the server you can change your implementation to echo back an origin in the Access-Control-Allow-Origin header. You cannot send back a list of origins, because browsers only accept a value that is either a single origin or null

See also

• CORS errors
• Glossary: {{Glossary("CORS")}} 
• CORS introduction
• Enable CORS: I want to add CORS support to my server