Polygon has been a fantastic service for stock prediction and analysis. Over the past year, I have worked to produce a high-quality model for prediction in the stock market. It has truly been a blast and I have learned a whole lot. However, dealing with basic stock data (such as closing prices) does not give all the information you would need, such as the cost per trade (the spread cost), as well as the amount of stock that is up for sale at any moment. The Polygon.io quote API allowed me to stream historical quotes for thousands of stocks to truly understand the dynamics of the market at any moment!
Polygon does so much more. Their API allows for parallel REST calls for grabbing stock aggregates, cryptos, forex and more! They even offer live streaming of quotes and trades as they happen in real-time. This was the service I needed for my project. If you are interested in market analysis, check out more about their historical RESTful APIs and live Websocket APIs.