A gap is a jump between one candle's close and the next candle's open, with no trading in between. On a stock chart they're common — the market shuts overnight and reopens at a new price. In forex the market runs around the clock on weekdays, so gaps are rarer, but they happen, mainly over the weekend and around big news.
Why forex gaps
- Weekend gaps. The market closes late on Friday and reopens on Sunday evening. Anything that moves price over the weekend — an election, a geopolitical shock, a central-bank statement — shows up as a jump between Friday's close and Sunday's open, because nobody could trade in between.
- News gaps. Around major data or a surprise rate decision, price can move so fast that lower-timeframe charts show a gap where liquidity briefly vanished.
Types of gap
The classic labels come from stocks but map onto forex well enough:
- Common gap — small, inside a range, usually closed quickly.
- Breakaway gap — price leaps out of a range and starts a new move.
- Runaway gap — a jump in the middle of an existing trend, showing it still has force.
- Exhaustion gap — a jump near the end of a move, often the last gasp before a turn.
Do gaps fill?
"Gaps always fill" is a half-truth traders repeat too confidently. Price often does return to the pre-gap level — weekend gaps fill fairly often, sometimes within hours. But a gap caused by a genuine change in value, like a shock rate cut, can stay open for weeks or never fill at all. Betting the account on a fill is betting that nothing real happened, which isn't a bet you always win.
Say GBP/USD closes Friday at 1.2700 and opens Sunday at 1.2650 — a 50-pip gap down. If it fills, price climbs back to 1.2700, worth £500 at £10 a pip. If the gap was a real repricing, it may keep falling instead. The size gives you a hint: a small gap inside a quiet range is a fair fill candidate, while a wide gap on a fresh Sunday headline is the market repricing, not an edge to fade.
The risk EAs forget
A stop-loss does not protect you across a gap. If price opens past your stop, you're filled at the next available price, not the level you set — and that slippage can be large. An EA holding trades over the weekend carries this risk on every open position, every Friday.
This is the practical point for automated traders. A backtest fills your stop at the exact level; the live market fills it wherever Sunday opens. The difference stays quiet until the weekend a gap opens straight through your stop. Some traders flatten open positions before the Friday close to sidestep it; others accept the risk and trade smaller into the weekend. Either is a defensible choice — pretending the gap can't happen is not.
The Karnek note
Karnek is read-only and can never trade, so it can't close a position before a weekend — but it does record where your fills actually landed against the stops you set. After a gap, that's the difference between the loss you planned for and the one you took. Seeing it in your own numbers is how weekend risk stops being abstract.
Written and reviewed by the Karnek Research team. Last updated August 2026.
Educational content only - not financial advice. Past performance does not predict future results. Trading carries significant risk.