The Donchian channel, and why it excludes today

What it means

The plainest levels on this site: no smoothing, no constant, no convention. The upper line is the highest high of the last twenty bars and the lower is the lowest low.

The channel excludes the current bar. That is the original definition and it is the part that matters — a channel including the current bar could never be exceeded by it, so 'price is at the top of its range' would be true by construction rather than by observation.

How we detect it

The engine reports the two levels and whether the last close sits above, inside or below them.

A window in which the high equals the low has no channel, and the engine says so rather than drawing a line of zero width.

When the read carries information

• The window is long enough to describe a range a reader would recognise.
• The instrument trades continuously enough that twenty bars is twenty comparable bars.

When it misleads

• One spike sets the channel for the whole window, and the level it leaves behind describes that spike rather than a level anything respected.
• In a trend the channel is exceeded constantly, and each exceedance means less than the last.
• It is a range description, not a zone: this product's support and resistance zones are built from repeated touches, which a Donchian line does not require.

How it reaches you

One line giving the two levels and where the close sits against them.

Neither level is offered as somewhere to act.