Swift Performance can keep headers of the original request. If you are using a plugin which send custom headers you can keep them for the cached version as well.
It can be useful if you are using a plugin which adds extra headers, like X-Frame-Options, or X-Content-Type-Options, etc.
If you enable this option, it will keep all headers, except Content-Encoding, and Set-Cookie headers. Of course you can add more exceptions with Exclude Headers option.