About a year ago I wrote a few scripts and spreadsheets to calculate the historical performance of various passive investment portfolios. There is portfoliovisualizer.com but if you are not from the US it's less relevant because everything is calculated with respect to the US dollar, and you cannot combine funds from other countries (say from the EU).

In the past month I managed to turn it into a web app with the goal of giving individuals better tools for financial education. It allows you to build a portfolio composed of a few index funds (ETFs or mutual funds) and simulate its historical performance. It currently works with 7 currencies and includes funds from the US, EU, UK, Canada and Israel. Intentionally, only broad-market, passive index funds are included.

If all of this doesn't mean much to you, you can visit the examples page to get a taste of some interesting portfolios. Here is an interesting example: For the past 22 years, US long-term treasuries had very similar returns to the S&P 500 (cherry-picked dates, but still interesting) [1].

On the technical side: The backend is a simple Flask app. A task runs once a day in the background to fetch the latest prices of ETFs and mutual funds from 20+ sources (central banks, stock exchanges). Frontend is Tailwind for CSS and a bit of native Javascript with d3. Everything runs on a $10/mo VPS.

This is my first web app and there is still a lot of room for improvement so any feedback is welcome.

Thanks in advance!

[1] https://pumbaa.app/backtest?b=1&currency=USD&initialBalance=...