High-frequency trading (HFT) is automated trading at extreme speed — microseconds — using co-located servers (physically next to the exchange), specialized hardware, and algorithms that react faster than any human possibly could. HFT firms are a major share of daily volume, and they're the subject of a lot of retail mythology.
What they actually do
Most HFT is market making and arbitrage, not directional betting. Firms continuously quote bids and offers, capturing tiny spreads across enormous volume, and they arbitrage fleeting price differences between venues (keeping the NBBO tight). They make money on razor-thin edges repeated millions of times — not on predicting where SPY closes.
Why retail can't compete on speed
You will never beat an HFT firm's co-located, hardware-optimized latency — that race is over before it starts, and it's the wrong race. HFT competes on microseconds; retail edges live on a completely different timescale (seconds to days) and in different signals. Trying to out-speed HFT is a losing game; ignoring the speed race and competing where they don't is the sane move.
You can't out-run HFT, and you don't need to. Their game is microseconds; yours is a completely different clock.
What it means for you
HFT mostly makes markets more efficient and spreads tighter for you — a benefit, not an enemy. Where it matters: it's why the book is fast and full of fleeting orders, and why displayed size can be deceptive. A retail-appropriate system doesn't fight for microseconds — it removes human latency and competes on a read and discipline that operate on a timescale where speed isn't the whole game.