IBKR offers the following API types:

• Trader Workstation (TWS API) - offers the most features and is made available to any clients with trading access.
• WT Web API - offered to white-branded advisors and introducing brokers and provides streaming and historical data…

IB Gateway is a standalone, Java-based software application with a minimal graphical user interface that is used by API and FIX/CTCI users to connect to IBKR for trading.

• In the IB API mode of operation, after choosing API Type "IB API" on the login screen, IB Gateway serves as a lightweight alternative to TWS which provides full API functionality but with a simple user interface used only for modifying API-relevant settings. Unlike TWS, IB Gateway does not give the user the ability to view their account, or perform other tasks such as placing orders without the use of a connected API program. A potential advantage for API users of using IB Gateway as opposed to TWS is that it requires fewer system resources…

A paid market data subscription is typically required to receive real time (live) market data via the API offerings. Once subscribed to the appropriate package, real time data is available via the TWS API in the following ways:

• Top of Book (Level 1) Streaming Data…

TWS settings are saved separately for live and paper account users and need to be configured independently for each.  To configure, select the Edit and then Global Configuration options from the TWS menu and then the API and Settings from the Configuration pane. Then check the box for…

We provide to our account holders a variety of proprietary trading platforms at no cost and therefore does not actively promote or offer the platforms or add-on software of other vendors. Nonetheless, as our principal trading platform, the TraderWorkstation (TWS), operates with an open API, there are numerous third-party vendors who create order entry, charting and various other analytical programs which operate in conjunction with the TWS for purposes of executing orders through us. As these API specifications are made public, we are not necessarily aware of all vendors who create applications to integrate with the TWS but do offer a program referred to as the …

For security purposes, IBKR does not support automatic login into the TWS or IB Gateway. Both applications are designed in a manner which requires each user to manually enter their credentials into the user interface. …

The TWS API can be downloaded here.

Please consult the TWS API documentation for installation instructions and information regarding the usage of the API…

Tick-by-tick data is available via the TWS API, and corresponds to the data received in the Time & Sales window of TWS. It is possible to request both real-time and historical tick-by-tick data. Please see the relevant section of the TWS API documentation…

Fundamental data is not available via the API. However, calendar and event data can be retrieved from the Wall Street Horizon Event Calendar. To access this data via the API, it is necessary to have the appropriate API specific subscription.

For more information on this functionality and the available data, please consult the…

While it is possible to connect an API application to a free trial account, neither real-time market data nor historical candlesticks are provided for any product that requires a paid subscription. 

Note…

We encourage you to visit the Trading API Solutions page of the IBKR website for general information about our API offerings. You can also refer directly to the TWS API …

Please see the Troubleshooting & Support section of the TWS API documentation for general troubleshooting suggestions and logging instructions.

Error messages sent by the TWS are handled by the EWrapper.error() callback function. When an error event occurs, it will be delivered to error(), and will contain the originating request/order ID (if applicable), a numeric error code and a brief description of the error. For further information on error handling and associated error codes, please consult the TWS API…

IBKR does not allow a single user name to operate multiple sessions concurrently. Operating multiple trading applications for a given account simultaneously requires a separate user name (for information on adding another user, see: Can I create a second user name for my account?…

Delayed market data (streaming and historical bars) can be retrieved using the TWS API, if the data is available. In the case of streaming data, it will be necessary to explicitly switch to the delayed or delayed-frozen market data types prior to calling the EClient.reqMktData() function…

Historical market data via the API maintains it's own set of limitations, separate to those of real time market data. For information on these limitations, please see the documentation…