When you read about how to create and consume a pre-signed url on this guide, everything is really easy. You get your Postman and it works like a charm in the first run.
Then you open your browser, try your usual $.ajax() and send your PUT operation, and you hit the cold iced wall of AWS error message, a simple <Code>SignatureDoesNotMatch</Code> that will steal hours from your productivity.
So here I come to save you and give you a free working example of how to upload a file directly to AWS S3 from your browser. You are wellcome :).