Nasdaq's first 15 minutes of the New York cash session on a trending day can carry a third or more of the entire day's eventual range inside them. That is the premise the opening range breakout rests on: whatever price does in a short window right after a session begins says something real about the day's directional intent, and trading a break of that window's high or low tries to capture whatever momentum is still left once the range resolves.
The idea is decades old and simple enough to describe in one sentence, which is exactly why it gets abused. A breakout strategy with no filters trades every session's open range and loses on every choppy day, and choppy days outnumber trend days. The version worth trading adds three or four honest filters before the entry, not after a losing week.
Defining the opening range
The range itself is just the high and low price prints during a fixed window right after the open. On Nasdaq and the S&P, that window is usually the first 15 to 30 minutes of the New York cash session, 9:30 to 9:45 or 9:30 to 10:00 Eastern. On forex, there is no single bell, so traders use the London open, roughly 3am New York time, and mark the first 30 to 60 minutes there instead. Shorter windows catch more breakouts and more false ones. Longer windows catch fewer trades but each one carries a more established range behind it. Pick one window per instrument and keep it fixed; switching window length after a losing trade is how a strategy becomes hindsight.
The classic entry, and its filters
The raw entry is a stop order placed just beyond the range high for longs and just beyond the range low for shorts, so the market triggers you automatically the moment it breaks. Three filters make this survivable rather than a coin flip dressed as a system. First, a trend filter: only take the breakout in the direction price was already leaning into the open, using yesterday's close or the overnight session bias, since a breakout against the prevailing lean fails more often than it works. Second, a range width filter: a range that is unusually narrow for the instrument, say under 15 points on Nasdaq versus a normal 30 to 40, tends to produce whipsaw breaks in both directions and is often better skipped. Third, a news filter: skip the setup entirely on days with a major scheduled release inside or right after the range window, since the break in that case reflects the headline, not structure.
A worked ORB on Nasdaq
Nasdaq opens the New York session at 17,820 and trades a 15 minute opening range from 17,805 to 17,850, a normal 45 point range for the instrument. Yesterday closed strong and the overnight session leaned higher, so the long side passes the trend filter, and there is no major data release scheduled before 10am, so the news filter passes too. A buy stop sits at 17,853, three points above the range high to avoid a marginal poke. Price triggers the long at 17,853. The stop goes at 17,798, seven points below the range low, because a genuine breakout should not immediately give back the entire range it just broke out of; if it does, the breakout failed. That is a 55 point risk. The target is the measured move, the range's own height projected from the breakout point: 45 points added to 17,853 gives a target near 17,898, a little over 0.8 to 1 reward to risk on this particular range, which is why the trend and news filters matter so much to the trades that get taken at all. On a $10,000 account risking 1 percent, $100 divided by 55 points at $1 per point gives roughly 1 contract.
Where it fails
The setup's worst enemy is a range day: price opens, breaks the range, immediately reverses, breaks the other side, and repeats until both sides have stopped out a breakout trader. This is common enough that some version of a two strikes rule helps: after one failed breakout in a session, skip the second signal unless the market has clearly shifted from range to trend behavior. Treating every day as a trend day is the single biggest reason ORB systems disappoint traders who only backtested the good months.