Virtual Colossus

Bringing the world's first electronic computer to you in digital form

Find Out More

What was Colossus and why a virtual one?

Colossus was the name of a series of computers developed by British codebreakers in 1943-1945 to help in the cryptanalysis of the Lorenz cipher. After the war, the Colossus computers were destroyed and all plans and information was required to be incinerated.

In 1992, Tony Sale and his team began the ambitious task of rebuilding a working Colossus from scraps of information and a few photos - they succeeded and you can see this running for real at The National Museum of Computing in Bletchley Park.

Tony Sale also wrote a virtual version of this amazing machine in 2001, but it's real tricky to get running as it was written for a very old version of Internet Explorer.
See if you want to give it a go.

To honour his memory and to make sure this code and it's story was not lost, I have rewritten from scratch a new Virtual Colossus using current browsers based on his original logic engine code. My hope is that more people will get to know this incredible story about the first computer.

What do I need to know to run it!
Instructions for use


It's not just COLOSSUS in name so use your browser zoom to see the big picture.

PC: Use Ctrl with +/- or with 0 for 100% or use Ctrl and mouse wheel
Mac: Use Command and +/- or with 0 for 100%
Tablet/Phone: Just pinch zoom as normal

Click or swipe switches

Try clicking above or below switches, on setting plugs and on rotary dials to set.

If you have touch screen, try swiping switches to set.

Look for Info Boxes

Look for the helpful blue info boxes. These give extra information about panels you can interact with and some options and selections.


Download a basic run-through of the available controls and what they do.

We recommend printing this out and having it to hand ... Colossus does not have a user friendly interface!

Get Instructions

View Scenarios to run yourself

A series of intercept scenarios for you to run on Colossus!

What does it do?

Credits and links

A number of people I need to say thanks and tip my hat to...

The Rebuild Team

Tony Sale and the rebuild team .. without their foresight and hard work, the details of this marvelous machine could have been lost forever and we certainly would not have been able to see it actually running!

Tony's original website is still available here and contains a lot of information including his original Virtual Colossus software. .. The National Museum of Computing .. Bletchley Park

Margaret Sale and Rich Sale for their permission to use the original code and information from Tony's website.

The engineers behind Colossus

Tommy Flowers .. A true genius and way ahead of his time, Allen Coombs, Dr Arnold Lynch and all the engineers at Dollis Hill

The geniuses at Bletchley Park

Brigadier John Tiltman .. A giant among cryptanalysts
The Bill Tutte Memorial Fund .. "Bill Tutte achieved one of the greatest intellectual feats of World War Two by breaking the extremely complex Lorenz code without ever seeing the machine that generated it."
Captain Jerry Roberts and all the codebreakers in the Testery. Without these people's code breaking skills and their daily breaking of the Lorenz wheels, Colossus would have been unable to function.

Plus all the other people who worked hard at Bletchley Park including all the Wrens(WRNS) who were the first computer operators in the world!

Also .. original 1940s IBM Typewriter image from his online museum, used with permission.

FuseMetrix Group .. My employers who put up with me nattering about Colossus and allow me space on their servers to run this website!

Let me know what you think!

Have I got something wrong, it doesn't work quite correctly on your computer or maybe you just want to say hi - check my Facebook or Twitter pages

Martin Gillow