This script plots the extended session highest high and lowest low levels. It works on any time frame from 1 minute to daily.
Please note that during the extended session, TradingView stops updating the daily chart. This means that once the script is loaded on a daily chart, it will not be updated until the market opens, unless you manually reload the layout (Ctrl+R). For this reason, it is recommended to use a multi-timeframe layout, so when the pre/post market line is near the extended session high/low on the daily chart, you can compare these values with those on an intraday chart of the same ticker.
The extended session high/low are important for day traders because they represent the maximum and minimum limits within which the trades have taken place during the extended trading hours. This can make them levels of support/resistance that can be useful for planning trend following, reversal and range-bound strategies. By displaying the extended session high/low on the daily chart, traders can also see if there are any significant levels nearby that are related to the daily time frame, such as trendlines, support/resistance levels, or moving averages. This can help the trader evaluate whether there is enough room for a price movement in the direction of his trading strategy.