If you're looking to invest in the US stock market, these popular online brokers offer commission-free trading, user-friendly platforms, and a range of tools for beginners to advanced investors. Here's a quick overview of some of the most commonly used ones:

Robinhood

Focus: Beginners & Mobile-First Trading
Simple, commission-free app for stocks, ETFs, options, and crypto—great for new investors with no minimums.
Website: https://robinhood.com/

Fidelity Investments

Focus: Full-Service Investing
Excellent research, zero-commission trades, strong customer support, and tools for all levels of investors.
Website: https://www.fidelity.com/

Charles Schwab

Focus: Comprehensive Trading & Education
Wide range of investments, thinkorswim platform for advanced users, and top-rated research and support.
Website: https://www.schwab.com/

Vanguard

Focus: Low-Cost Passive Investing
Ideal for index funds and ETFs with ultra-low fees—perfect for long-term, buy-and-hold strategies.
Website: https://investor.vanguard.com/

Interactive Brokers

Focus: Advanced & Active Traders
Low-cost global access, powerful tools, and features for experienced users and high-volume trading.
Website: https://www.interactivebrokers.com/

Webull

Focus: Active & Day Trading
Advanced charting, extended-hours trading, and community features—all commission-free.
Website: https://www.webull.com/

Important Note
Most of these brokers offer $0 commissions on US stocks and ETFs, but other fees (like options contracts, margin rates, or inactivity) may apply. Always compare current fees, features, and reviews, and do your own research before opening an account or investing.