# Fathom Flow Accelerations, exhaustions, slowdowns and absorption levels. ## What the indicator shows - Exhaustion: a push runs out of steam despite the volume (filled triangle on the Fathom chart). - Slowdown: aggression fades near an extreme (hollow triangle on the Fathom chart). - Acceleration: volume suddenly takes off over one or two bars (rectangle on the Fathom chart). - Control (C) and extreme (E) lines, drawn when price leaves a consolidation; on the Fathom chart, the control line is solid and the extreme line dotted. - The `label` field combines A (absorption, a breakout against the consolidation’s delta) or P (a breakout with it), then C or E. Example: `AC` is the control line after an absorption. ## How to use it - An acceleration in the direction of the move confirms it. An exhaustion or a slowdown near an extreme warns that it is losing strength, often before a reversal. - After a consolidation, the control (C) and extreme (E) lines are reference levels to follow the breakout. A breakout marked A (`AC`, `AE`) went against delta: the aggression was absorbed. - Tune each signal separately: `weak` to see more of them, `strong` to keep only the most pronounced. - Do not show a drawing with `visible: false`. ## How it is computed - Acceleration (rectangle): volume is summed over 1-second windows. Once per bar, the largest window volume seen since the previous check is compared with the last 50, itself included: if it reaches their mean + k standard deviations (k = 3.25 with `weak`, 4.75 with `medium`, 6.5 with `strong`), a rectangle covers the price range of the checked window (`start` -0.5, or -1.5 when it began in the previous bar). It stays extended until a bar body crosses it, 12 bars at most. - Exhaustion (filled triangle): over the last n bars (n = 5 with `weak`, 8 with `medium`, 10 with `strong`), the sum of deltas and the sum of volumes are tracked. When the sign of that delta sum flips after at least n/2 bars (rounded down), the phase that ends is compared with the last 10: if its peak volume reaches their mean + 0.5 standard deviation while its peak absolute delta stays within their mean + 1 standard deviation (1.25 with `weak`), an exhaustion is flagged opposite to the phase (`up: true` after a selling phase). `variant` 0: computed on volumes; `variant` 1: the same on the number of buying and selling trades. - Slowdown (hollow triangle): a profile of buying and selling volume per tick is tracked while price stays within an 8-tick spread; beyond it, and at every session open, it restarts from the trade’s price. The threshold is the mean − k standard deviations (k = 0.45 with `weak`, 0.8 with `medium`, 1.05 with `strong`) of the largest per-tick volume of the 35 previous profiles, truncated. When a bar closes, if the profile spans at least 3 ticks and, on its 3 lowest ticks, selling volume stays within the threshold while decreasing toward the low, a bullish slowdown is placed at the profile’s low; likewise at the high with buying volume. - Consolidation: at least 5 bars whose bodies fit within 85% of the average true range of the last 21 bars. It extends as long as no bar closes more than 20% of that range beyond its bodies (with `absorption: "strong"`, as long as no wick goes that far). - Lines: when price leaves a consolidation, if its volume, its delta or its bars’ volume reaches its threshold (mean + k standard deviations of the last 25 consolidations or of the last 50 consolidation bars, this one included, k rising from `weak` to `strong`), two lines are drawn. Control (`control`): the POC of the consolidation’s bars, or, with `levelMode: "aggressive"`, the edge of their bodies on the breakout side. Extreme (`extreme`): with `levelMode: "conservative"`, the wick opposite to the breakout; otherwise, the edge of the 70% value area opposite to the breakout. A line stays extended until a bar body crosses it, `projectionBars` bars at most. - `label`: `A` (absorption) when the breakout goes against the consolidation’s delta, `P` when it goes with it, then `C` (control) or `E` (extreme). `side` gives the sign of that delta, `up` the breakout direction. ## When it updates - Each drawing is sent when its anchor bar (`bar`) closes, sent again on every change, then sent final once it can no longer change: an exhaustion is final as soon as it is sent; a rectangle or a line, once it stops being extended (`active: false`, with its `end`). - While it is the latest one, a slowdown can move to another anchor bar (`bar`, `start`) and price, and switch from `visible: true` to `false` or back: it is visible while a consolidation is in progress, or when its price is within the body of the last consolidation, at most 5 bars after it. It becomes final when a new slowdown replaces it, or at the end of the week, sometimes with `visible: false`: do not show it. In `confirmed` mode it then arrives directly with `visible: false`. - `` is the drawing type and `` the `YYYY-MM-DD` date of the week’s Sunday reopen. The ordinal is shared by all kinds: for a given kind, the numbers are not consecutive. - Weekly reset: on the first trade of the Sunday reopen (6:00 pm New York time), the week’s last bar is processed, rectangles and lines still extended stop (`active: false`, with their `end`), drawings still in progress are sent final and the computation starts over. - **Identifier**: `flow-tracker` - **Objects received**: `drawing` - **Historical cost**: 1 compute unit per trade ## Subscribe The same `params` work in [real time](https://fathomcharts.com/docs/websocket.md), on [historical data](https://fathomcharts.com/docs/history.md) and in exports. Parameters you omit take their default values. **Subscribe message** ```json { "t": "subscribe", "sub": "flow-tracker", "instrument": "NQ.front", "indicator": "flow-tracker", "params": { "absorption": "medium", "acceleration": "medium", "exhaustion": "medium", "levelMode": "conservative", "projectionBars": 10, "slowdown": "medium", "timeframe": 60 }, "mode": "live", "from": "live" } ``` ## Parameters As soon as a parameter differs from its default, the subscription counts as a [custom configuration](https://fathomcharts.com/docs/limits.md#how-limits-are-counted). To change a parameter, open a new subscription. | Parameter | Type | Default | Allowed values | Unit | Description | | ---------------- | ------- | -------------- | ----------------------------------------------------------------------------------------------- | ---- | --------------------------------------------------------------------------------------------------------------------------------- | | `absorption` | choice | `medium` | `weak` · `medium` · `strong` | — | Sensitivity of the control and extreme lines: `weak` (more lines), `medium` or `strong` (only after the heaviest consolidations). | | `acceleration` | choice | `medium` | `weak` · `medium` · `strong` | — | Acceleration sensitivity: `weak` (more signals), `medium` or `strong` (fewer, more pronounced signals). | | `exhaustion` | choice | `medium` | `weak` · `medium` · `strong` | — | Exhaustion sensitivity: `weak` (more signals, on short pushes), `medium` or `strong` (fewer signals, on longer pushes). | | `levelMode` | choice | `conservative` | `conservative` · `medium` · `aggressive` | — | Placement of the control and extreme lines, from farthest from the breakout (`conservative`) to closest (`aggressive`). | | `projectionBars` | integer | `10` | 1 to 1,000 | bars | Maximum length of the control and extreme lines, in bars; a line stops earlier when a bar body crosses it. | | `slowdown` | choice | `medium` | `weak` · `medium` · `strong` | — | Slowdown sensitivity: `weak` (more signals), `medium` or `strong` (fewer, more pronounced signals). | | `timeframe` | integer | `60` | `1` · `5` · `10` · `15` · `30` · `60` · `120` · `180` · `300` · `600` · `900` · `1800` · `3600` | — | Bar duration in seconds: from 1 second (`1`) to 1 hour (`3600`). | ## Objects received Each object keeps the same `id` from one update to the next. Its data is in the `data` field. Prices are in ticks: multiply them by the instrument’s tick size (`GET /v1/instruments`) to get points. ### `drawing` (sent in progress) Drawing; in progress while it can still change. `id` format: `::`. The object is sent in progress (`final: false`), then sent again on every change; each version fully replaces the previous one. Once it can no longer change, its last version carries `final: true`, except for objects whose description says they are removed without a final version. | Field | Type | Unit | Present | Description | | --------- | ------------------------------------------------------------------------------- | -------------- | --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `kind` | string · `acceleration` \| `exhaustion` \| `slowdown` \| `control` \| `extreme` | — | always | Type: acceleration (rectangle), exhaustion and slowdown (triangles), control and extreme (lines). It is also the first segment of the `id`. | | `active` | boolean | — | sometimes | Rectangle or line still extended to the right. | | `bar` | string | timestamp (ns) | always | Start of the anchor bar. | | `end` | number | bars | sometimes | End of the drawing, in bars from the anchor bar, rounded to a tenth (can be fractional); present on final rectangles and lines. | | `high` | integer | ticks | sometimes | Top of a rectangle. | | `label` | string · `AC` \| `PC` \| `AE` \| `PE` | — | sometimes | Line: `A` (absorption) when the consolidation breakout goes against its delta, `P` when it goes with it; then `C` for the control line, `E` for the extreme line. `AC` is the control line after an absorption. | | `low` | integer | ticks | sometimes | Bottom of a rectangle. | | `price` | integer | ticks | sometimes | Price of a triangle or a line. Exhaustion: 3 ticks below the bar’s low (`up: true`) or above its high; slowdown: low or high of the tracked profile. | | `side` | string · `buy` \| `sell` | — | sometimes | Line: sign of the consolidation’s delta (`buy` positive or zero, `sell` negative). | | `start` | number | bars | always | Start of the drawing, in bars from the anchor bar, rounded to a tenth: can be fractional or negative (-0.5, or -1.5 for an acceleration over two bars). Matching time, in nanoseconds: `BigInt(bar) + BigInt(Math.round(start × timeframe × 1e9))` (`bar` is in nanoseconds, `timeframe` in seconds). | | `up` | boolean | — | always | Bullish direction: positive or zero delta for an acceleration, exhaustion of a selling phase, slowdown at the low, upward consolidation breakout for a line. | | `variant` | integer | — | sometimes | Exhaustion: `0` when detected on volumes, `1` on the number of buying and selling trades. Both variants can flag the same bar, at the same price. | | `visible` | boolean | — | always | `false`: the signal is not valid, do not show it. Only a slowdown can switch to `false`, then back to `true`, while it is in progress; it can end with `false`, and then arrives that way in `confirmed` mode. | ## Example messages Messages as the WebSocket sends them to the subscription above, taken from a real NQ session. [Historical data](https://fathomcharts.com/docs/history.md) returns the same objects, with the same `cursor`, without the `sub` field. **Final object** ```json { "sub": "flow-tracker", "cursor": "20720.2457.0", "t": "upsert", "id": "exhaustion:2026-09-20:1101", "final": true, "ts": "1790209200076693991", "data": { "kind": "exhaustion", "bar": "1790209140000000000", "start": 0, "price": 122953, "up": true, "visible": true, "variant": 0 } } ``` **Object in progress** ```json { "sub": "flow-tracker", "cursor": "20720.3293.1", "t": "upsert", "id": "slowdown:2026-09-20:1104", "final": false, "ts": "1790209860030424303", "data": { "kind": "slowdown", "bar": "1790209800000000000", "start": 0, "price": 122940, "up": false, "visible": true } } ``` **Object in progress** ```json { "sub": "flow-tracker", "cursor": "20720.3454.0", "t": "upsert", "id": "control:2026-09-20:1105", "final": false, "ts": "1790209920141869579", "data": { "kind": "control", "bar": "1790209860000000000", "start": 0, "price": 122927, "up": true, "visible": true, "active": true, "label": "AC", "side": "sell" } } ``` **Object in progress** ```json { "sub": "flow-tracker", "cursor": "20720.3454.1", "t": "upsert", "id": "extreme:2026-09-20:1106", "final": false, "ts": "1790209920141869579", "data": { "kind": "extreme", "bar": "1790209860000000000", "start": 0, "price": 122913, "up": true, "visible": true, "active": true, "label": "AE", "side": "sell" } } ``` **Final object** ```json { "sub": "flow-tracker", "cursor": "20720.3770.0", "t": "upsert", "id": "slowdown:2026-09-20:1104", "final": true, "ts": "1790210280761988745", "data": { "kind": "slowdown", "bar": "1790209800000000000", "start": 0, "price": 122940, "up": false, "visible": true } } ``` **Final object** ```json { "sub": "flow-tracker", "cursor": "20720.4035.0", "t": "upsert", "id": "control:2026-09-20:1105", "final": true, "ts": "1790210520086671473", "data": { "kind": "control", "bar": "1790209860000000000", "start": 0, "end": 10, "price": 122927, "up": true, "visible": true, "active": false, "label": "AC", "side": "sell" } } ``` ## JSON schemas To validate or type your data: the JSON schemas of the parameters and of `data`, also available from `GET /v1/indicators`. The SDK can [generate types from them](https://fathomcharts.com/docs/sdk.md#indicator-types). **Parameters schema** ```json { "$schema": "https://json-schema.org/draft/2020-12/schema", "$id": "https://fathomcharts.com/schemas/flow-tracker/params.json", "type": "object", "additionalProperties": false, "properties": { "absorption": { "description": "Sensitivity of the control and extreme lines: `weak` (more lines), `medium` or `strong` (only after the heaviest consolidations).", "type": "string", "default": "medium", "enum": [ "weak", "medium", "strong" ] }, "acceleration": { "description": "Acceleration sensitivity: `weak` (more signals), `medium` or `strong` (fewer, more pronounced signals).", "type": "string", "default": "medium", "enum": [ "weak", "medium", "strong" ] }, "exhaustion": { "description": "Exhaustion sensitivity: `weak` (more signals, on short pushes), `medium` or `strong` (fewer signals, on longer pushes).", "type": "string", "default": "medium", "enum": [ "weak", "medium", "strong" ] }, "levelMode": { "description": "Placement of the control and extreme lines, from farthest from the breakout (`conservative`) to closest (`aggressive`).", "type": "string", "default": "conservative", "enum": [ "conservative", "medium", "aggressive" ] }, "projectionBars": { "description": "Maximum length of the control and extreme lines, in bars; a line stops earlier when a bar body crosses it.", "type": "integer", "default": 10, "minimum": 1, "maximum": 1000 }, "slowdown": { "description": "Slowdown sensitivity: `weak` (more signals), `medium` or `strong` (fewer, more pronounced signals).", "type": "string", "default": "medium", "enum": [ "weak", "medium", "strong" ] }, "timeframe": { "description": "Bar duration in seconds: from 1 second (`1`) to 1 hour (`3600`).", "type": "integer", "default": 60, "enum": [ 1, 5, 10, 15, 30, 60, 120, 180, 300, 600, 900, 1800, 3600 ] } } } ``` **`data` field schema** ```json { "$schema": "https://json-schema.org/draft/2020-12/schema", "$id": "https://fathomcharts.com/schemas/flow-tracker/data.json", "title": "drawing", "type": "object", "additionalProperties": false, "properties": { "kind": { "description": "Type: acceleration (rectangle), exhaustion and slowdown (triangles), control and extreme (lines). It is also the first segment of the `id`.", "type": "string", "enum": [ "acceleration", "exhaustion", "slowdown", "control", "extreme" ] }, "active": { "description": "Rectangle or line still extended to the right.", "type": "boolean" }, "bar": { "description": "Start of the anchor bar.", "type": "string", "pattern": "^[0-9]+$" }, "end": { "description": "End of the drawing, in bars from the anchor bar, rounded to a tenth (can be fractional); present on final rectangles and lines.", "type": "number" }, "high": { "description": "Top of a rectangle.", "type": "integer" }, "label": { "description": "Line: `A` (absorption) when the consolidation breakout goes against its delta, `P` when it goes with it; then `C` for the control line, `E` for the extreme line. `AC` is the control line after an absorption.", "type": "string", "enum": [ "AC", "PC", "AE", "PE" ] }, "low": { "description": "Bottom of a rectangle.", "type": "integer" }, "price": { "description": "Price of a triangle or a line. Exhaustion: 3 ticks below the bar’s low (`up: true`) or above its high; slowdown: low or high of the tracked profile.", "type": "integer" }, "side": { "description": "Line: sign of the consolidation’s delta (`buy` positive or zero, `sell` negative).", "type": "string", "enum": [ "buy", "sell" ] }, "start": { "description": "Start of the drawing, in bars from the anchor bar, rounded to a tenth: can be fractional or negative (-0.5, or -1.5 for an acceleration over two bars). Matching time, in nanoseconds: `BigInt(bar) + BigInt(Math.round(start × timeframe × 1e9))` (`bar` is in nanoseconds, `timeframe` in seconds).", "type": "number" }, "up": { "description": "Bullish direction: positive or zero delta for an acceleration, exhaustion of a selling phase, slowdown at the low, upward consolidation breakout for a line.", "type": "boolean" }, "variant": { "description": "Exhaustion: `0` when detected on volumes, `1` on the number of buying and selling trades. Both variants can flag the same bar, at the same price.", "type": "integer" }, "visible": { "description": "`false`: the signal is not valid, do not show it. Only a slowdown can switch to `false`, then back to `true`, while it is in progress; it can end with `false`, and then arrives that way in `confirmed` mode.", "type": "boolean" } }, "required": [ "kind", "bar", "start", "up", "visible" ] } ```