Intercept an HTTP request at browser end to alter some html content

Question

I would like to do as follows. What would be the best way? A general answer will also be fine.

I would like to intercept an HTTP request at the client end to alter some

Answer 1

Local HTTP proxy is possible and most generic approach.

I.e. you can use Fiddler to see if it works for you. I supports modifying requests/responses in addition to regular watching for traffic.