To tell what the web server is, right inside of a webpage

#webdev #http #webserver

Sometimes if we start a local webserver, or if we use other online pages, we would like to find out what webserver it is, and it is possible to do it right inside of the webpage. We can fetch something, and look at the response header by res.headers.get("Server"):

fetch("foo.txt").then((res) => {
  document.querySelector(
    "#server-note"
  ).innerHTML = `The server is ${JSON.stringify(res.headers.get("Server"))}`;
});

Demo: https://jsfiddle.net/KennethKinLum/80td3s4f/

The server for

Webserver	in the header
Node.js's `live-server`	nothing `(null)`
Ruby's `ruby -run -e httpd . -p 8080`	`WEBrick/1.4.2 (Ruby/2.6.3/2019-04-16)`
Python 2's `python -m SimpleHTTPServer 8080`	`SimpleHTTP/0.6 Python/2.7.16`
Python 3's `python3 -m http.server 8080`	`SimpleHTTP/0.6 Python/3.8.2`
JSFiddle	`nginx`
Codesandbox	`cloudflare`
macOS Big Sur's webserver	`Apache/2.4.46 (Unix)`