ThinkorSwim is available for free to TD Ameritrade customers. As long as you can log in using your TD Ameritrade account, you can use the trading platform at no cost.
You can download the ThinkorSwim software for Windows, Mac, or Linux using this link
According to the ThinkorSwim commissions page, there is no fee for online stock and ETF trades. It's the same for options trading, but you have to pay $0.65 fee per contract. A $2.25 fee per contract is applied to Futures and Options on Futures.
There is no monthly fee on any of ThinkorSwim trading account including taxable, non-taxable, and retirement accounts.
ThinkorSwim supports both live trading and paper trading. Before logging in to the platform, you have the option to choose between a live account and a paper trading account.
ThinkorSwim clients can trade during extended hours (pre-market and after-hours trading sessions).
ThinkorSwim does not support auto trading at the moment. However, you can explore their APIs to assist with your development.
The ThinkorSwim mobile app is available in the Apple App Store. This means you can run it on your iPhone, iPod touch, or iPad.
ThinkorSwim is available in Canada through TD Waterhouse Discount Brokerage.