A swing low is the mirror of a swing high: a local turning point at the bottom of a price move. The strict definition: a candle whose low is lower than the lows of the candles on either side (the simplest version uses one candle on each side; tougher windows use two or three).
Swing lows are the foundation of trend identification on the downside. Higher swing lows confirm an uptrend (each pullback stops at a higher level than the prior pullback). Lower swing lows confirm a downtrend (each rally fails to a lower level than the prior rally). They also anchor candidate support zones — multiple swing lows clustered near the same price form a structural floor.
The size of a swing low matters. A small intraday trough is a swing low but a noisy one. A trough visible on the daily or weekly is a significant swing low and carries structural weight. Always read swing lows on the time frame relevant to your trade.
The earliest structural warning that a downtrend may be ending is a higher swing low — a pullback that bottoms above the prior low. This precedes the higher-high confirmation by at least one swing, which is why traders watching structure can position earlier than indicator-only readers.
Swing lows are also the invalidation reference for longs: a close back below the most recent swing low typically invalidates a bullish bias, because the uptrend''s defining sequence (higher lows) is broken. Many traders cluster stop orders just below the most recent swing low — meaning a sweep through that low can briefly extend the move before reversing. Marking swing lows is therefore useful both for identifying your own setups and for understanding where the rest of the market''s stops live.