Capital.com marketData.subscribe

messagemarketData.subscribeCapital.com WebSocket APIWebSocketLive prices

Subscribes to live price updates for a list of epics. Capital.com's page gives 40 as the most epics. An answer confirms each epic, then a quote message arrives for each price update.

Risk warning: CFDs and spread bets are complex instruments and come with a high risk of losing money rapidly due to leverage. You can lose money on these products, and each provider publishes its own loss figure under FCA rules. You should consider whether you understand how they work and whether you can afford to take the high risk of losing your money. Automated and API trading can amplify losses through bugs, connectivity failures and runaway orders.

Independent and unofficialopen-api.capital.comchecked 12 Oct 2026

This is a message of the Capital.com WebSocket API, not an HTTP endpoint. It has no method and no path: it is sent as JSON over an open WebSocket connection.

The message

Name: marketData.subscribe
Direction: Request, sent by the client
Carried by: WebSocket. Capital.com's page says to ping the service at least once every 10 minutes to keep the connection alive.
WebSocket address: wss://api-streaming-capital.backend-capital.com/connect
Answered by: quote

Fields

The vendor's page does not say which of these fields are required or always present.

Name	Type	Description
destination	Not stated	Names the message, in the way a path names a REST call. Here it is marketData.subscribe.
correlationId	Not stated	An id of your own. The answer carries the same value, which is how an answer is matched to its request.
cst	Not stated	The token that identifies the client. It is the CST value returned when a session is started over REST.
securityToken	Not stated	The token that identifies the account in use. It is the X-SECURITY-TOKEN value returned when a session is started over REST.
payload.epics	Not stated	The epics to subscribe to, as a list of strings. The page gives 40 as the maximum number.

What arrives

marketData.subscribe: The confirmation of the subscription. Price updates then arrive as quote messages.

The vendor's page does not say which of these fields are required or always present.

Name	Type	Description
status	Not stated	OK in the vendor's example of a successful answer.
destination	Not stated	The destination of the request it answers: marketData.subscribe.
correlationId	Not stated	The correlationId the request carried.
payload.subscriptions	Not stated	An object with one entry for each epic asked for. In the vendor's example the value is PROCESSED.

Sample

Written by this site from the fields recorded on this page. It has not been run against a terminal, a server or an account, and the values in it are placeholders. No credential is typed into it: where a field holds one, the placeholder says where it comes from. Nothing is entered on this site.

{
  "destination": "marketData.subscribe",
  "correlationId": "1",
  "cst": "<the CST token of your session, from your own environment>",
  "securityToken": "<the X-SECURITY-TOKEN of your session, from your own environment>",
  "payload": {
    "epics": [
      "OIL_CRUDE"
    ]
  }
}

Limits that apply at Capital.com

Limit	Value	Scope	Source
Headline limit	10/s per user	user	open-api.capital.comchecked 18 Sep 2026