Firefox developer tools currently only shows the 'preflighted' request as OPTIONS and GET; however it does not indicate which request is preflighted. In contrast Chrome clearly shows that which request is preflighted with the method column showing GET+preflight and the OPTIONS request is labeled as preflight in the initiator column. I suggest Firefox implement something similar because it helps web developers to debug CORS more efficiently.

Thank you for the report!

Could you please provide a simple page or point to an existing page we could use to reproduce the problem on our machines?
Having a reproducible test case usually helps a lot, thank you!

Yeah sure. I have an exmaple of a Chinese video website named Bilibili as a test case which uses GET+preflight frequently to load video segments
Example:
https://bilibili.com/video/BV1Hy4y1S7JB

Thanks for the link.

So, Chrome is Showing a "Preflight" link in the Method column and an icon-link in the Initiator column.
Are those the two things you are referring to?

Honza

Yes. Exactly what I am talking about