JustPortOpt
Pick a set of tickers, set your weights, and see where your portfolio sits against 3,000 simulated ones on the efficient frontier.
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The problem. Choosing portfolio weights by feel hides the trade-off you are actually making — a little more expected return usually costs a little more risk.
What it does. Pulls one year of daily closes from Yahoo Finance, annualises return and volatility from the covariance matrix, then simulates 3,000 random weightings. Your portfolio is plotted as a star over that cloud, coloured by Sharpe ratio, with the max-Sharpe portfolio marked as the reference point.
Scope. An educational tool, not investment advice. Prices come from yfinance, the risk-free rate is assumed to be zero, and nothing is persisted between sessions.