Faust issues HEAD requests to a potentially large number of HTTP URLs, and outputs the HTTP response codes in TSV format.
Faust is a tiny Rust program (<100 lines) built on top of reqwest and tokio. It can easily scale to tens of thousands of parallel requests, and process thousands of requests per second on even a modest machine.
If you have Rust and Cargo installed:
$ cargo install faust
$ time faust <<EOF
> http://www.google.com
> https://www.google.com
> http://github.com
> https://github.com
> http://cloudflare.com
> https://cloudflare.com
EOF
http://cloudflare.com/ 301 https://www.cloudflare.com/
http://github.com/ 301 https://github.com/
http://www.google.com/ 200 OK
https://cloudflare.com/ 301 https://www.cloudflare.com/
https://github.com/ 200 OK
https://www.google.com/ 200 OK
real 0m0.100s
user 0m0.005s
sys 0m0.009s
Faust easily scales to tens of thousands of connections, but needs
an adequate number of allowed file descriptors. If it refuses to run for this reason, you may need to adjust the limits in /etc/security/limits.*.
If you are behind NAT, such a large number of connections may crash cheap home routers or severely degrade their performance.