Opening Range Breakout (ORB) is a common day trading strategy used by day traders around the globe.
The objective is to mark Today's High and Low range of a stock at a specific time after the market opens.
Trades are taken in the same direction at which the price moves out of this range.
15 minutes, 30 minutes and 1 hour are the most popular marked Ranges when day trading the Opening Range Breakouts.

Yesterday's High and Low values are used when defining the Previous Day Range (PRB). Trades are initiated in the same direction at which the price breaks out of the Previous Day's range.

Why is this important for daytrading ?

Price moving above yesterday's High implies increasing demand. Similarly when price moves below Yesterday's Low reflects the increasing supply.
Day traders often use this in combination with other day strategies to increase the odds.

Intraday trend is defined by strong price and volume movement of a stock during the day.

Day traders look for stocks with continuous movement of price in the same direction combined with increasing volume.

Stocks creating New Intraday high's or low's are potential candidates for day traders who want to ride the trend.

This strategy is based on the assumption that stocks that rise will continue to rise and stocks that fall will continue to fall, during the day.

Demand and Supply in a stock is evident when the price starts to move in the same direction for the past few days.

This happens when investors start to accumulate these stocks or begin to distribute their holdings.

Day traders often find these daily Gainers and Losers interesting for spotting a daytrading opportunity.
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2 & 3 day's Consecutive Gainers and Losers are short listed for trading this strategy.

Support and Resistance levels based on Classical Pivot Formula works like a magnet.

You will be surprised to watch how intraday price reacts at these predefined levels. The levels are based on Yesterday's High, Low and Close. Price moving above or below these predefined levels signifies strength or weakness.
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The Classical Pivot indicators are available on most trading platform. Price Crossovers on Pivot Line, R1 and S1 are monitored for trading this strategy.

It is important to learn the Previous Day Range Breakout Strategy, before we know why the price rejections at these levels becomes relevant.

Intraday price get rejected at Previous Day's High or Low when today's price attempts to counter trend the daily trend cycle.

Price rejections at Yesterday's Low from above is favored for long intraday trading.

Price rejection at Yesterday's High from below is favored for short intraday trading.

Narrow Range 7 (NR 7) forms when Yesterday's trading range, high - low, is the narrowest of the last 7 trading days.
After identifying a NR 7 opportunity, traders wait for the price to move above or below this narrow range during the day.

Trades are taken in the same direction at which the price moves out of Yesterdays Narrow Range. This strategy works on the assumption that today's breakout will determine the new short term trend cycle for that stock.
This is very similar to other Range Breakout strategies discussed earlier.

Intraday Volume is the Fuel that powers the success of any given day trading strategy. Higher relative day volume should be a top priority when screening stocks for day trading.

Stocks that have significantly gained or lost during the day, has a higher chance of moving in the same direction than trading on a dormant stock and expecting it to make irrational moves during intraday.