Which broker is best for automated trading?

For most retail automation: Alpaca if you want the smoothest programmatic experience and first-class paper trading; Charles Schwab if you want automation attached to a full-service brokerage with an official API; Webull if that's where your account and habits already live. The honest answer is that once a platform abstracts the broker behind an adapter, the strategy behaves identically everywhere — the differences that remain are order-type support (fractional shares, trailing stops, market-on-close), account types offered, and where your other assets sit. Pick the broker you'd want even without automation; the automation layer should adapt to it, not the other way around.