Because swing traders enter and exit trades within days or weeks, end-of-day data that is available on the Internet for free is sufficient for them. But day traders need real time intraday data because they enter and exit trades within a few hours, and often within a few minutes. Unfortunately, real time market data is not free, and you need to pay a monthly fee to your broker (or in my case to DAS Trader since I do not use the Interactive Brokers’ platform) depending on the type of market data you need access to. Which market data you should buy depends on the market that you are trading. If you are planning to trade in the Canadian market, you need real time Toronto Stock Exchange (TSX) data. I largely limit my trading to the U.S. markets because of its high volume (liquidity) and volatility, therefore I need Nasdaq real time data. Unfortunately, without real time market data, you cannot day trade properly.
If you also are planning to primarily trade in the U.S. markets, contact your broker and ask for the real time Nasdaq TotalView Level 2 data feed. You may need to pay a monthly fee for your data depending on your broker.