What qualifies as a no-demand bar in VSA?

The common definition is an up close, a spread narrower than recent bars, and volume lower than each of the previous two bars. Many practitioners add context requirements, such as appearing after weakness or into resistance, before treating it as tradeable. Exact thresholds vary by author, so tools implementing it make those cutoffs explicit parameters.

Is a no-supply bar a buy signal?

Not by itself. VSA treats it as evidence, not a trigger: it says sellers failed to show up on the decline. It becomes actionable when the background already shows strength, such as accumulation or stopping volume, and the following bar confirms by closing back up. In a genuine downtrend, low-volume dips are normal and prove nothing.

Who created Volume Spread Analysis?

Tom Williams, a former London syndicate trader, systematized VSA from Wyckoff's principles and his own professional experience, publishing it in Master the Markets and building analysis software around it. His framing gives the discipline its flavor: every bar interrogated for what professional money was doing, with the quiet bars, the no-demand and no-supply labels, treated as the professionals' refusals, which are often more informative than their appearances.

Why must volume be below the previous two bars?

It is a stricter absence test. Volume below one prior bar happens constantly and proves nothing; below both of the last two bars, on a narrow-spread directional close, the move is demonstrably unaccompanied, which is the entire claim the label makes. The two-bar convention comes from Williams' formulation, and implementations keep it as the standard cutoff precisely because loosening it floods charts with meaningless flags.

Does a no-demand bar in an uptrend signal reversal?

Usually not, and this is the discipline's most-taught nuance. In a market whose background shows strength, quiet narrow pullback and pause bars are normal resting behavior; the no-demand label only turns bearish when the background has already shown weakness, distribution, upthrusts, heavy supply, so the quiet rally reads as a test that failed to attract buyers. Background first, bar second is the VSA reading order.

Do NSND bars work on tick-volume feeds?

With reduced confidence. The labels' logic runs through actual participation, and tick counts, the stand-in on spot forex and some crypto feeds, measure activity events rather than size, so the absence inference weakens. On centrally reported futures and equities the volume leg means what VSA assumes; elsewhere, treat the labels as spread-and-activity reads, corroborate with structure, and expect more noise.

No-demand / No-supply Bars

No-demand and no-supply bars are classifications from Volume Spread Analysis (VSA), the discipline Tom Williams developed out of Wyckoff's effort vs result logic. They are Volume & Order Flow concepts. The Library holds 1 implementation, ready to run on Vela.

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No-demand / No-supply Bars

Indicator

What are No-demand / No-supply Bars?

No-demand and no-supply bars are classifications from Volume Spread Analysis (VSA), the discipline Tom Williams developed out of Wyckoff's effort vs result logic. A no-demand bar is an up bar (close above the prior close) with a narrow spread and volume lower than each of the previous two bars: price rose, but no professional money chased it, so the rally is suspect. A no-supply bar is the mirror image: a down bar with a narrow spread on volume below the previous two bars, a dip with no real selling behind it.

Neither bar means anything on its own in VSA. They are read against the background: no-supply appearing after signs of strength is treated as a successful test that clears the way higher, while no-demand appearing after signs of weakness argues the upmove is a rally to sell into.

The lineage matters for reading them correctly. Williams, a former syndicate trader who systematized his approach in Master the Markets, framed every bar as a question about professional participation: the no-demand and no-supply labels are absence findings, the professionals declining to join a move, which is why the volume must sit below both prior bars rather than merely below average. They live inside a larger VSA taxonomy alongside stopping volume, tests, and upthrusts, and the discipline's core rule is that background analysis precedes bar reading: the same narrow, quiet bar is bullish evidence in an accumulating market and bearish evidence in a distributing one.

Modern practice keeps the logic and tightens the engineering. Detection tools like the Library's NSND study make the thresholds explicit parameters, narrowness relative to recent spreads, the two-bar volume comparison, optional background filters, so the classification is reproducible rather than eyeballed. Confirmation discipline is standard: the bar nominates a scenario and the next bar's close votes on it. And the input caveats are the volume family's usual ones: the inference assumes meaningful volume data, judged against a relative volume baseline, and modern order-flow tools can check directly, via volume delta, what VSA infers indirectly from spread and total volume.

How to identify no-demand and no-supply bars

Three mechanical checks and one contextual one, with the context carrying the meaning.

1Classify the close: above the prior close makes the candidate a no-demand bar, below it a no-supply bar.
2Require a narrow spread: the bar's high-to-low range visibly below recent bars, the low-effort signature.
3Require quiet volume: below each of the previous two bars, the absence test that separates these labels from ordinary pullback bars.
4Read the background first: the same bar is bullish after demonstrated strength and bearish after demonstrated weakness, and means little in a vacuum.
5Demand confirmation: the following bar's close in the expected direction is the conventional trigger, the quiet bar itself being evidence rather than entry.

How traders use it

As continuation filters: in a market showing background strength, no-supply pullbacks are used to time longs; in background weakness, no-demand rallies are used to time shorts.
As test confirmation: after stopping volume or a shakeout, a later no-supply bar suggests sellers are exhausted, with the next bar's close commonly required as confirmation.
As a warning against chasing: a breakout attempt built on no-demand bars lacks the volume signature VSA expects from genuine markup.
In automated screens: detector tools parameterize the spread and volume thresholds explicitly, so the bars are flagged consistently and the trader's judgment is reserved for the background call.
Cross-checked with order flow: where delta data exists, a no-supply bar whose tape genuinely shows absent aggressive selling carries more weight than one inferred from totals alone.

NSND bars vs related volume reads

Effort vs Result: The Wyckoff law is the principle: volume spent should produce movement. The VSA bar labels are packaged verdicts under that law, no-demand and no-supply being the specific case of absent effort on a directional close, pre-classified for scanning.

Volume Spike: Opposite anomalies: the spike is effort arriving in excess, read for climax and absorption; the NSND bar is effort failing to arrive at all. VSA needs both, since campaigns announce themselves with volume and betray themselves with its absence.

Volume Delta: Delta measures aggressor balance directly from the tape; VSA infers participation from spread and total volume, a chart-level approximation of the same question. Where both exist, delta audits the inference, and their agreement is the stronger read.