# Fathom Zones Directional effort zones on 40-tick range bars, with the 20-period EMA of the closes. ## What the indicator shows - A buy zone marks a fast upward push backed by buying delta; a sell zone, a fast downward push backed by selling delta. On the Fathom chart, buy zones are blue and sell zones coral. - The range bars and the 20-period EMA of their closes are published with the zones, to put them in the context of the trend. ## How to use it - When price comes back into a zone, watch how it reacts: a buy zone often acts as support, a sell zone as resistance. - Place the zone against the EMA: a buy zone above the EMA goes with the trend, and so does a sell zone below it. - A zone crossed by a bar body ends: the level did not hold. ## How it is computed - 40-tick range bars, with no parameter: a bar runs until the trade that would take its high-low spread beyond 40 ticks, and that trade opens the next bar. A new bar also opens at every session open (6:00 pm New York time). Bars are numbered from 0 from the start of the week. - A finished bar is an effort bar when four conditions hold: its body goes the way of its delta (ask − bid; close ≥ open for a positive or zero delta, close < open for a negative one); the absolute delta is 10% to 40% of the bar’s volume; the delta per body tick, `delta / (|close − open| + 1)` truncated, is at most 14 contracts in absolute value; the bar formed in 45 seconds at most (duration truncated to the second), from its first trade to the trade that opens the next one. - As soon as two consecutive effort bars go the same way, a push starts: its bounds start from the high and low of these two bars, then widen with each further effort bar the same way. - The first bar that is not an effort bar that way ends the push and creates the zone, whose `start` is that bar’s index. The zone covers the half of the push where it started: the lower half for a buy zone, the upper half for a sell zone, so its bounds can fall on a half tick. - The 20-period EMA of the closes starts at the bar with index 21: its first value is that bar’s close, then `EMA = previous EMA + (close − previous EMA) × 2/21`. - The three object kinds have no field telling them apart in `data`: read the `id` prefix (`bar:`, `ema:`, `zone:`). `` is the `YYYY-MM-DD` date of the week’s Sunday reopen; the index of a bar or an EMA value is the last segment of its `id`. ## When it updates - Each range bar is sent once, final, when it closes, with its EMA value from index 21 on. - A zone is sent in progress as soon as it is created, then final (`active: false`, with its `end`) on the first of these events: a bar body crosses it (below its bottom for a buy zone, above its top for a sell zone), it has covered 21 bars (`start` to `start` + 20), or a new session opens (6:00 pm New York time). A zone can end on the very bar that creates it. - The snapshot keeps the last 32 final objects of all kinds together: the more numerous bars and EMA values can leave no room for any final zone. - Weekly reset: on the first trade of the Sunday reopen (6:00 pm New York time), the week’s last bar is sent, zones still in progress are sent final (`active: false`, with their `end`), then bars, indices and the EMA start over; nothing carries over to the new week. - **Identifier**: `effort-zones` - **Objects received**: `bar`, `ema`, `zone` - **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": "effort-zones", "instrument": "NQ.front", "indicator": "effort-zones", "params": {}, "mode": "live", "from": "live" } ``` ## Parameters This indicator has no parameters: omit `params` or send `{}`. ## 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. ### `bar` (sent final) Finished range bar. ``: `YYYY-MM-DD` date of the week’s Sunday reopen; ``: number of the bar from the start of the week (0, 1, 2…), read from the `id` (`data` has no `index` field). `id` format: `bar::`. Each object is sent once, final (`final: true`). | Field | Type | Unit | Present | Description | | ------- | ------- | -------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `close` | integer | ticks | always | Close. | | `high` | integer | ticks | always | High. | | `low` | integer | ticks | always | Low. | | `open` | integer | ticks | always | Open. | | `start` | string | timestamp (ns) | always | Timestamp of the bar’s first trade. To place a zone in time, read the `start` of the bar whose index equals the zone’s `start` (or `end`); the bar of the `end` is only published when it closes. | ### `ema` (sent final) EMA value at the close of bar `` (the same index as in that bar’s `id`). `id` format: `ema::`. Each object is sent once, final (`final: true`). | Field | Type | Unit | Present | Description | | ------- | ------ | ----- | ------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `value` | number | ticks | always | 20-period EMA of the closes, at the close of bar ``. It starts at the bar with index 21, on its close, then `EMA = previous EMA + (close − previous EMA) × 2/21`. No `ema` object exists for bars 0 to 20 of the week. | ### `zone` (sent in progress) Zone; in progress while it is active. `` is its `start`. `id` format: `zone::`. 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 | | -------- | ------------------------ | ----- | --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `active` | boolean | — | always | `true` while the zone is extended; `false` once it is final. | | `end` | integer | bars | sometimes | Index of the range bar after the end of the zone: the bar still in progress when the zone ends, only published when it closes; at the end of the week, the index that would follow the week’s last bar, which no bar carries. On expiry, `end` = `start` + 21. Absent while the zone is active. | | `high` | number | ticks | always | Top of the zone; can fall on a half tick. | | `low` | number | ticks | always | Bottom of the zone; can fall on a half tick. | | `side` | string · `buy` \| `sell` | — | always | Direction of the push that formed the zone: `buy` for a positive or zero delta, `sell` for a negative delta. | | `start` | integer | bars | always | Index of the range bar that created the zone, counted from the start of the week like the index of bar `id`s (not a timestamp). | ## 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": "effort-zones", "cursor": "20720.110.0", "t": "upsert", "id": "bar:2026-09-20:2939", "final": true, "ts": "1790208062570437091", "data": { "start": "1790207999116757165", "open": 123012, "high": 123044, "low": 123004, "close": 123006 } } ``` **Final object** ```json { "sub": "effort-zones", "cursor": "20720.110.1", "t": "upsert", "id": "ema:2026-09-20:2939", "final": true, "ts": "1790208062570437091", "data": { "value": 123066.85128768138 } } ``` **Object in progress** ```json { "sub": "effort-zones", "cursor": "20720.32179.2", "t": "upsert", "id": "zone:2026-09-20:3114", "final": false, "ts": "1790230140362667235", "data": { "side": "buy", "high": 122357, "low": 122258, "active": true, "start": 3114 } } ``` **Final object** ```json { "sub": "effort-zones", "cursor": "20720.34641.2", "t": "upsert", "id": "zone:2026-09-20:3114", "final": true, "ts": "1790231072263560767", "data": { "side": "buy", "high": 122357, "low": 122258, "active": false, "start": 3114, "end": 3135 } } ``` ## 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/effort-zones/params.json", "type": "object", "additionalProperties": false, "properties": {} } ``` **`data` field schema** ```json { "$schema": "https://json-schema.org/draft/2020-12/schema", "$id": "https://fathomcharts.com/schemas/effort-zones/data.json", "anyOf": [ { "title": "bar", "type": "object", "additionalProperties": false, "properties": { "close": { "description": "Close.", "type": "integer" }, "high": { "description": "High.", "type": "integer" }, "low": { "description": "Low.", "type": "integer" }, "open": { "description": "Open.", "type": "integer" }, "start": { "description": "Timestamp of the bar’s first trade. To place a zone in time, read the `start` of the bar whose index equals the zone’s `start` (or `end`); the bar of the `end` is only published when it closes.", "type": "string", "pattern": "^[0-9]+$" } }, "required": [ "start", "open", "high", "low", "close" ] }, { "title": "ema", "type": "object", "additionalProperties": false, "properties": { "value": { "description": "20-period EMA of the closes, at the close of bar ``. It starts at the bar with index 21, on its close, then `EMA = previous EMA + (close − previous EMA) × 2/21`. No `ema` object exists for bars 0 to 20 of the week.", "type": "number" } }, "required": [ "value" ] }, { "title": "zone", "type": "object", "additionalProperties": false, "properties": { "active": { "description": "`true` while the zone is extended; `false` once it is final.", "type": "boolean" }, "end": { "description": "Index of the range bar after the end of the zone: the bar still in progress when the zone ends, only published when it closes; at the end of the week, the index that would follow the week’s last bar, which no bar carries. On expiry, `end` = `start` + 21. Absent while the zone is active.", "type": "integer" }, "high": { "description": "Top of the zone; can fall on a half tick.", "type": "number" }, "low": { "description": "Bottom of the zone; can fall on a half tick.", "type": "number" }, "side": { "description": "Direction of the push that formed the zone: `buy` for a positive or zero delta, `sell` for a negative delta.", "type": "string", "enum": [ "buy", "sell" ] }, "start": { "description": "Index of the range bar that created the zone, counted from the start of the week like the index of bar `id`s (not a timestamp).", "type": "integer" } }, "required": [ "side", "high", "low", "active", "start" ] } ] } ```