Portfolio123 is a game-changer for… Portfolio123 is a game-changer for stock investors, providing a powerful platform for the design, simulation, and deployment of quantitative financial models. It also has stock screening, charting (including YChart style), trading (via Interactive Brokers and Tradier), macro economics charting, watchlists, an earnings center, cross-section series plotting, external data importer, a data API, stock news, stock summary snapshots, stock comparison tool, sector/Industry performance, fundamental and estimate summaries, a user forum and more (really). In the near future, machine learning will be supported. It's not just another retail-level tool; it's the only one that I’ve found to work in practice. To find something better, I suspect you'd have to go professional and spend significantly more. I've been a loyal subscriber for over a decade, which speaks volumes about its effectiveness. Is there a downside? Sure, building successful trading models is hard work, but with dedication and focus, it's possible to be successful. Whether you're researching stocks, building and simulating quantitative models, or managing accounts, Portfolio123 has what you need.

Excellent site for backtesting equity trading strategies Excellent site for testing stock and ETF trading strategies. P123 provides a thorough point-in-time database with a powerful and flexible engine to simulate backtests of systems. And they integrate with Interactive Brokers to automate applying those strategies to live trading.

More Fun Than Video Games! I Joined P123 Apr 28, 2004, and I have been Investing in systems I developed ever sense then. I currently am receiving 60% of my family annual income from my investments. P123 is more fun than video games! I LOVE it! Denny Halwes

Extremely powerful and unique tool Extremely powerful and unique tool. Im not aware of any other like it on the market. Despite having no formal finance background I have decisively beaten my benchmark index for multiple years with real money investing in companies that are off most other people's radar. Once you get used to systematically investing with a model you will wonder how you did it any other way (or how you could do it any other way). The staff is extremely knowledgable and responsive. The user community is generous and supportive. Beyond that, the tool is just fun to research, test theories and play around with.

Toxic environment Toxic environment that stigmatizes creative, productive, diverse critiques as so-called "unconstructive" and "repetitive" and condones toxic personal attacks.