Love Terry Pratchett? Check your X-Clacks-Overhead!
March 26, 2023

Tags: #literatur #programmierung #tipp

> A man is not dead while his name is still spoken.
>   ⸺ _Going Postal_, Chapter 4 prologue

## About the Signal

`X-Clacks-Overhead` is a non-standardised HTTP header based upon the fictional work of the late, great, [Sir Terry Pratchett](https://en.wikipedia.org/wiki/Terry_Pratchett).

In Terry Pratchett's science-fantasy [Discworld series](https://en.wikipedia.org/wiki/Discworld), "The Clacks" is a network infrastructure of Semaphore Towers, that operate in a similar fashion to telegraph – named "Clacks" because of the clicking sound the system makes as signals send.

In Sir Terry’s novel "Going Postal", the story explains that the inventor of the Clacks – a man named Robert Dearheart, lost his only son in a suspicious workplace accident, and in order to keep the memory of his son alive, he transmitted his son’s name as a special operational signal through the Clacks to forever preserve his memory:
<!--more-->
**GNU John Dearheart**

**G**: Send the message onto the next Clacks Tower.
**N**: Do not log the message.
**U**: At the end of the line, return the message.

The nature of the 'GNU' code would keep the name of his son forever transmitting through The Clacks network so long as the network still existed.

## GNU on the Internet

As a way to preserve the memory of Sir Terry Pratchett, the users of the [SubReddit for the Discworld series](https://www.reddit.com/r/discworld/) came up with [the idea behind the `X-Clacks-Overhead` HTTP Header](https://www.reddit.com/r/discworld/comments/2yt9j6/gnu_terry_pratchett/). It allows web authors to silently commemorate someone through the use of a non-invasive header that can be transmitted from server to server, or server to client without operational interference.

At the time of writing, Mozilla.org (makers of the Firefox web browser), the makers of Debian (a popular Linux Operation System), and Xml.com (a major repository of standards information) are examples of some of the backbones of the Internet who transmit the Signal "GNU Terry Pratchett". _We do, too._

You would only know the header is present if you analysed the transmission headers of your content requests on web sites serving the header.

## Visualise it in Firefox

Using the Firefox Extension [X-Clacks-Overhead](https://addons.mozilla.org/en-US/firefox/addon/x-clacks-overhead/) by Sixthhokage1, a bug-fixed fork of the original extension [GNU\_Terry\_Pratchett](https://addons.mozilla.org/en-US/firefox/addon/gnu_terry_pratchett/) by Rob Grundy, you can _visualise the X-Clacks-Overhead content_. The extension’s little icon will even flash the original Clacks code at you! If you mouse over the icon, the Clacks overhead message will be displayed.

## Read more

- The [X-Clacks-Overhead](https://xclacksoverhead.org/) site shows sites carrying the signal, and allows to add your own.
- Visit [GNU Terry Pratchett](http://www.gnuterrypratchett.com/) to find out how to include the signal on your site, blog, email, etc.
- Buy the "Going Postal" paperback at [Amazon.de](https://amzn.to/3JMdfjU) (affiliate link).

_Keep the legacy of Sir Terry Pratchett and other beloved ones alive forever. For as long as their names are still passed along the Clacks, Death can’t have them._

**Note to my children:** I’d love to know _you_ including _my name_ in the `X-Clacks-Overhead` of your sites and blogs, whenever I can’t be with you anymore…