This is a web application I made before European football championshop of 2021. It is based on a very similar simulator I made for the World cup 2018.
I created it because I wanted a way to be able to simualte different outcomes in the tournament to be able to see possible scenarios, for instance in betting purposes. I couldn't find any other simulators like this one online that took into account every result of each game. My simulator allows user to enter exact match results for each game, whereas the simulators I found online only allowed the usual 1, X or 2 options.
If the user enters a result for every single match including the last match, the final, the app will generate a code that can be shared to view ones result to other people. The code is a long string that can be entered via a GET-parameter and then decompressed to view the results.