https://en.wikipedia.org/wiki/MIME

"In the Hypertext Transfer Protocol (HTTP) for the World Wide Web, servers insert a MIME header field at the beginning of any Web transmission. Clients use the content type header to select an appropriate viewer application for the type of data indicated."

A fan of "let's enable the program to do everything" philosophy I am not. This idea is embodied in the so-called "modern" web browser and a countless number of other "apps". Alas, this design, perhaps justified on "convenience" grounds (or so-called "user experience"), has been abused, e.g., for commercial purposes. One casualty of the abuse might be speed. Other sacrifices might be reliability, resource usage, "privacy", "security", etc. The most important sacrifice for me in using "do everything" software is _control_

Instead I use a number of small command line clients for making HTTP requests ("web requests").^1 I can edit the source code and compile these applications quickly with low resources

The clients are request makers, not response viewers. The historical "select an appropriate viewer application" step remains, as I prefer it

This software is not slow. I seem to avoid the dissatisfaction that I see from commenters who use software that can "do everything"

1. Generally this is one application that accepts URLs on stdin and generates HTTP on stdout and another that accepts HTTP on stdin, makes connections and sends it, typically a TCP client. But since I use a local forward proxy that has a built-in httpclient I don't necessarily need those programs to make requests, e.g.,

   x=https://danluu.com/perf-opt/
   echo "@1;expert-mode on;httpclient GET $x"|socat stdio unix:/path/socket 

The proxy lets me control all the possible details of the requests (not through the built-in httpclient of course), including some details that can't be controlled using a gigantic, complicated, so-called "modern" browser