Market data vendors usually provide exchange data in two categories: real-time and delayed. Real-time market data is disseminated as soon as the information is publicly available.
Delayed market data is on a time lag that is usually 10-20 minutes behind real-time quotes. Some exchanges allow delayed data to be shown without any market data subscription, free of charge.
Customers receive free delayed market data for contracts to which they do not currently hold market data subscriptions when made available by the exchanges. Not subscribing to real time data has no impact on your order executions. However, you are required to have active trading permissions for the products you wish to trade.
Please Note: Delayed quotes are not provided for U.S. stocks on live accounts with IB LLC or owned by U.S. residents due to FINRA regulations.
More Information: Delayed Market Data Timing How do I subscribe to real-time market data? How do I manage my trading permissions?