https://hleb.dev/post/x-clacks-overhead/

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X-Clacks-Overhead

Dec 27, 2025

I am a big fan of Sir Terry Pratchett. His books influenced my sense
of humor and the way I look at things, far beyond just fantasy
literature. Some time ago, I added a small but meaningful detail to
this blog - the X-Clacks-Overhead HTTP header.

Post cover

This header is a reference to the "Going Postal" novel and the Clacks
system. In short, it is a quiet way to say "GNU Terry Pratchett" - a
signal that keeps his name moving through the network, not forgotten.

My blog is served with Cloudflare Pages. It supports custom HTTP
response headers via a plain text _headers file placed in the root
directory of your website, injecting headers according to the rules
you define.

Here's the relevant section from my _headers file:

/*
  X-Clacks-Overhead: "GNU Terry Pratchett"

That's it - every request for static assets and HTML gets the header.

If you want to check it yourself, open browser developer tools -
Network tab - inspect the response headers, or run:

curl -I https://hleb.dev

It does nothing useful. It changes nothing about performance or
functionality. But sometimes small, unnecessary things are exactly
what make the internet better.

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