What is high-frequency trading (HFT)?
In one line: High-frequency trading is a kind of algorithmic trading where firms use very fast computers to place and cancel huge numbers of orders in fractions of a second.
The short answer
High-frequency trading (HFT) is algorithmic trading built for speed. Firms place their computers right next to the exchange's computers to save tiny slivers of time.
They measure time in millionths of a second. A human click takes far longer than many of their whole trades.
What HFT firms actually do
Most HFT is not betting on where price goes next week. The common jobs are:
- Market making. Quoting a buy price and a sell price all day, and earning the small gap between them, the Spread. See Market maker.
- Arbitrage. Spotting the same thing priced slightly differently in two places, like an ETF and the stocks inside it, and closing that gap.
- Fast reactions. Reading news or data and adjusting quotes instantly.
A simple example
A stock shows a Bid and ask of $50.00 and $50.01. An HFT firm quotes both sides.
It buys 100 shares from a seller at $50.00. A moment later it sells 100 shares to a buyer at $50.01.
Profit: 100 × $0.01 = $1, before fees. Tiny. But repeated millions of times a day, across thousands of stocks. And it can go wrong: if price jumps before the second trade, the firm takes a loss.
Why it matters to you
You can't beat HFT on speed, and you don't need to. If you hold trades for minutes, hours or days, a millionth of a second doesn't matter.
What does matter: when markets panic, fast traders can pull their quotes. Spreads widen and Slippage grows. The flash crash of 2010 is the famous example.
A common mistake
Blaming every bad fill on HFT. Most of the time, a poor fill comes from using a Market order in a thin or fast market. A Limit order sets the worst price you'll accept.
You'll never be the fastest. Be the most patient. A trade planned on a 1-hour chart doesn't care about microseconds.
Questions
Is high-frequency trading legal?
Yes, in the US and most major markets. Specific tactics, like placing fake orders to trick others (called spoofing), are illegal.
Can a regular trader do high-frequency trading?
Not realistically. It needs special data feeds, servers at the exchange and big budgets.
Does HFT make markets better or worse?
People disagree. Supporters say it narrows spreads. Critics say liquidity can vanish in a crisis.
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