Making Quant Analysis and Trading accessible to everyone I knew about QuantConnect when I was desperately searching online for Options Historical data in the US markets. Everything else I found was expensive and required me a lot of manual handling. Not to say they weren't realistic at all (i.e. didn't consider company splits, adquisitions, etc.). QuantConnect and the open source lean framework made it very easy to implement trading algorithms (with a results very close to what I get in Interactive Brokers; including fees, splits, dividends, option assignments, etc.) at a very cheap cost (you just pay for the cloud computing resources). Being open source makes it very easy to figure out how to do things, however, they have interactive tutorials that will prepare anyone with basic development skills to implement real-live trading algorithms. Not to say the community is awesome and very helpful. QuantConnect is easily escalable for both small individuals and large corportations. Many organizations and hedge funds use it for their analysis and live trading.

Complex, difficult API, slow backtesting Extremely slow backtesting and very complex APi with bad documentation - be ready to spend many hours trying to understand the overly complex API that is changing all the time. And did I mention that support costs? So if a anything is complex you won't get answers from the staff unless you PAY them. I give them 2 stars as they have reasonably reliable data. The platform itself is only worth one star. note: if you ask about slowness or any other thing negative on their forum they delete the posts.

Great technology, accessible team, invaluable supporters of the ecosystem QuantConnect has been an invaluable partner for my personal trading and for a university class that I teach. The community is incredibly supportive, and the leadership team are accessible which is almost unheard of in trading platforms these days. In my class, my graduate level students have been able to personally engage and implement constructs like Fama French factors, and QuantConnect has been an active supporter to facilitate my students learning. It's incredible to join the community, have access to a variety of detailed trading algorithms, instructional videos, and see my students feel confident implementing week-to-week. I don't think there's anything like QuantConnect out there today, and I'm a big supporter of their efforts. I can't imagine my own trading or teaching my class without it!

Long time believer, first time promoter. I've been using Quantconnect for about two years but they've just released new capabilities for options research, based on user feedback, that prompted me to add a review. They listen to, care about, and build new features for their users (free features). Highly recommend.

Shady site Shady site not sure if the team behind are trustworthy with holding your algos data. I found other frameworks like backtrader that are easier to pick up and get working with quickly than LEAN. LEAN is poorly documenting making learning a huge hurdle. Also, I question the stability of their site because of the amount of bugs you can find in their UI and some that I encountered in plotting during backtrading. If you need an online IDE, Quantopian is far more reliable and documented and quicker to work with but still could have issues with data privacy.