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.

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.

Can only say good things! Over two (fun!) years the QuantConnect team have assisted me in (1) My programming...which at the beginning was all but non-existent. With this, the customer support, community help and other resources e.g. GitHub provided me with the required information to develop my algos. (2) Connectivity....I can connect one of my algos to one of my Interactive Brokers accounts in about 2 minutes. Its that easy. (3) Ability to license....Many of the systems I have developed over the last couple of years and submitted to the AlphaStreams marketplace are being licensed. Like any other endeavor in life - this takes hard work and a lot of effort. I have had no problems with backtest times - but obviously the times will depend on the amount of data being crunched in the background. So Im very happy - a friendly bunch of people doing real innovative stuff. I cant wait what the next few years bring!

Have been using QC for 3 years Have been using QC as an individual for 3 years, has been a smooth and consistent experience the entire time. Quantconnect makes building a trading algorithm highly accessible to anyone with an idea and a bit of coding knowledge. Handling all the background infrastructure for you, they make it easy to build your algorithm, backtest against market data, and even deploy it live with a supported brokerage. Sometimes it can be a bit difficult to learn the syntax and what a method does, but there is a lot of documentation available, as well as community forums. All this has really helped me focus on my strategy rather than building infrastructure from the ground up and I would definitely recommend them to anyone looking to try out quant finance or algorithmic trading.

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.