Robinhood - Free stock trading service.
OpenInsider - OpenInsider is an SEC Form 4 insider screener that allows you to monitor the insider trading filings for insider buying and selling.
Alpaca Data API - Free real-time stock market data API
Finviz Insider Trading - Finviz Insider Trading platform allows you to perform trades, investments, and transactions in the company’s stock shares.
SparkFin - Learn the markets for free, profit forever.
Sec Form 4 - Sec Form 4 is a real-time insider data providing platform that shows insider trades, transactions, buying, and selling data.