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    Is your browser actually sending the headers? Check your dev tools. Commented Aug 9, 2017 at 13:10
  • @JoeClay I am seasoned developer (mobile, backend) but rather new to web front-end development. Many tools are new for me - especially dev tools in brownser are not very good friend of mine yet. Can you suggest how to I check it on Chrome or Safari? Thanks Commented Aug 9, 2017 at 19:42
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    In Chrome, press F12 to open your dev tools, and then switch to the Network tab. When your application sends a HTTP request, it'll appear in the list, and you can click on it to view the headers/body of the request and response. See the docs for more info - learning how to use your browser's dev tools will help you loads if you're just starting out with web development :) Commented Aug 10, 2017 at 8:10
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    @JoeClay So the answer is no the browser does not send X-My-Custom-Header nor Authorization. Now the remaining questions are why? And how to fix it? Commented Aug 10, 2017 at 16:45
  • See stackoverflow.com/questions/42311018/… at Why does Fetch API Send the first PUT request as OPTIONS Commented Aug 12, 2017 at 18:55

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