ThinkorSwim
Thinkorswim (often written "ToS") is a trading platform — a piece of software you use to look at charts, place orders, and manage a brokerage account. It was originally built by a company called thinkorswim, which was acquired by TD Ameritrade, and TD Ameritrade itself was later folded into Charles Schwab after Schwab bought it. The platform still runs under the Schwab umbrella and remains widely used by active and casual traders alike.
Functionally, it works like most broker platforms: you fund an account, and thinkorswim gives you access to real-time (or delayed, depending on your setup) price charts, order entry screens, options analysis tools, and a scripting language called thinkScript that lets users build custom indicators and studies. Because it is free to use for account holders and has a deep feature set — options chains, paper trading, customizable layouts — it became a default choice for many retail traders rather than a niche or premium product.
The nuance beginners miss is that thinkorswim is a platform, not a broker in the sense of "a separate company you owe money to" — your account, your money, and your regulatory protections sit with the brokerage (now Schwab), while thinkorswim is the interface layer on top. Custom indicators or strategies built in thinkScript run inside this specific platform and generally don't transfer automatically to other software; if a trading firm or educator says they have "built indicators for thinkorswim," that means those tools are only usable if you're actually running that platform, not a universal add-on.
This term depends on a rule or threshold that changes over time, so no specific figure is quoted here. Confirm the current corporate ownership and branding status of thinkorswim/TD Ameritrade under Charles Schwab (Schwab has been migrating TD Ameritrade accounts and there has been public discussion about thinkorswim's platform future/rebranding). Verify current status directly against Charles Schwab's official announcements before publishing.
A day trader cares because the platform you use directly affects execution speed, order types available, charting flexibility, and whether the custom tools or strategies you've learned (like TT's indicators) actually work in your setup — switching platforms can mean losing access to tools you rely on.
A trader opens a brokerage account with Schwab, downloads the thinkorswim desktop app, and loads a custom thinkScript indicator that highlights a specific moving-average crossover on a 5-minute chart. That same indicator won't appear if the trader logs into a different broker's platform, even with the same underlying account type.
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