> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kalshi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Market Data

> Request margin order book snapshots and incremental updates through FIX

Market data is available on the dedicated **KalshiMD** session. It supports order book snapshots and incremental updates for margin markets. Subscriptions are identified by `Symbol<55>`.

`KalshiMD` does not support message retransmission. Use `ResetSeqNumFlag<141>=Y` on Logon.

## Message Flow

```mermaid theme={null}
sequenceDiagram
    participant Client as FIX Client
    participant KalshiMD

    Client->>KalshiMD: Logon (35=A, 141=Y)
    KalshiMD->>Client: Logon (35=A)
    Client->>KalshiMD: Snapshot + updates request (35=V, 263=1)
    KalshiMD->>Client: Snapshot (35=W) or Reject (35=Y)
    KalshiMD->>Client: Incremental updates (35=X)
    Client->>KalshiMD: Cancel by Symbol (35=V, 263=2)
```

## Market Data Request (35=V)

| Tag | Name                    | Type    | Required | Description                                                                                                                                                                                               |
| --- | ----------------------- | ------- | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 263 | SubscriptionRequestType | Char    | Y        | `0`=Snapshot, `1`=Snapshot plus updates, `2`=Disable previous snapshot plus update request                                                                                                                |
| 146 | NoRelatedSym            | Integer | C        | Number of `55=Symbol` entries in the repeating group that follows. Required for `263=0` and `263=1`. For `263=2`, the listed symbols are unsubscribed; omit to cancel all of the session's subscriptions. |
| 55  | Symbol                  | String  | C        | Repeating group field. The margin market tickers to subscribe to or cancel.                                                                                                                               |

```fix Example snapshot request theme={null}
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=0|146=1|55=BTC-PERP|
```

```fix Example snapshot-plus-updates subscription theme={null}
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=1|146=1|55=BTC-PERP|
```

```fix Example cancel a symbol theme={null}
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=2|146=1|55=BTC-PERP|
```

```fix Example cancel all subscriptions theme={null}
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=2|
```

## Market Data Snapshot Full Refresh (35=W)

Sent in response to a snapshot request and immediately after a snapshot-plus-updates subscription is accepted. Correlate by `Symbol<55>`.

| Tag | Name        | Type     | Required | Description                               |
| --- | ----------- | -------- | -------- | ----------------------------------------- |
| 55  | Symbol      | String   | Y        | Margin market ticker.                     |
| 268 | NoMDEntries | Integer  | Y        | Number of book levels.                    |
| 269 | MDEntryType | Char     | Y        | Repeating group field. `0`=Bid, `1`=Offer |
| 270 | MDEntryPx   | Price    | Y        | Book level price in dollars.              |
| 271 | MDEntrySize | Quantity | Y        | Book level size in contracts.             |

```fix Example snapshot response theme={null}
8=FIXT.1.1|35=W|49=KalshiMD|56=your-api-key|55=BTC-PERP|268=2|269=0|270=19.5000|271=10.00|269=1|270=19.5100|271=5.00|
```

## Market Data Incremental Refresh (35=X)

Sent after a subscribed market's aggregated book levels change or a trade occurs. Correlate by `Symbol<55>` on each entry.

| Tag  | Name           | Type     | Required | Description                                             |
| ---- | -------------- | -------- | -------- | ------------------------------------------------------- |
| 268  | NoMDEntries    | Integer  | Y        | Number of market data entries.                          |
| 279  | MDUpdateAction | Char     | Y        | Repeating group field. `0`=New, `1`=Change, `2`=Delete. |
| 55   | Symbol         | String   | Y        | Repeating group field. Margin market ticker.            |
| 269  | MDEntryType    | Char     | Y        | Repeating group field. `0`=Bid, `1`=Offer, `2`=Trade    |
| 270  | MDEntryPx      | Price    | Y        | Price in dollars.                                       |
| 271  | MDEntrySize    | Quantity | Y        | Size in contracts.                                      |
| 2446 | AggressorSide  | Char     | C        | Trade entries only. `1`=Buy, `2`=Sell.                  |

```fix Example incremental update theme={null}
8=FIXT.1.1|35=X|49=KalshiMD|56=your-api-key|268=1|279=1|55=BTC-PERP|269=0|270=19.5000|271=15.00|
```

```fix Example trade update theme={null}
8=FIXT.1.1|35=X|49=KalshiMD|56=your-api-key|268=1|279=0|55=BTC-PERP|269=2|270=19.5000|271=3.00|2446=1|
```

## Market Data Request Reject (35=Y)

Sent when a market data request cannot be accepted. Unknown market tickers are not currently rejected; the server sends an empty snapshot if it has no order book for the requested symbol.

| Tag | Name           | Type   | Required | Description                      |
| --- | -------------- | ------ | -------- | -------------------------------- |
| 281 | MDReqRejReason | Char   | N        | Reject reason.                   |
| 58  | Text           | String | N        | Human-readable rejection detail. |

### Common Reject Reasons (281)

* `2`=Insufficient bandwidth, including request or session symbol limits
* `4`=Unsupported `SubscriptionRequestType`