The close can be an important point to evaluate the market’s direction. But, the open is the most important number to watch all day. It has several important factors.

It shows the early morning strength or weakness

It is where the trading day begins and is the first barometer of market sentiment. A gap up shows strength but also sets the reversal trap. A gap up that fails will accelerate movement through the opening price

It can anchor any good intraday breakout system

The open is a great base for any price breakout. Adding and subtracting a value to the open serves as the basis of many intraday breakout systems. Analyzing a trend day shows a large range day with the open and close on the extremes.

It is the source of intraday stops

After the market moves towards a breakout, the open is the reversal magnet. Large funds will place stops there. If a long breakout falters a move to the open will accelerate through the price as funds exit through a small window.