API Update: Deprecation of 'limit' Field in WebSocket Connection Response

At BitMEX, we are committed to continually improving our platform and its infrastructure. As part of this ongoing effort, we are announcing an update to our WebSocket API.

The limit field currently sent in the WSRequestLimit response upon successful WebSocket connection will be deprecated and should no longer be relied upon by clients.

Effective Date and Time: 30 March 2026 at 06:00 - 09:00 UTC

What is changing?

When a client establishes a WebSocket connection, the server currently sends a WSRequestLimit message that includes a limit field. This limit field will be removed from the response.

Current response (before change):

{"info":"Welcome to the BitMEX Realtime API.","version":"2.0.0","timestamp":"2026-01-26T08:17:40.000Z","docs":" https://www.bitmex.com/app/wsAPI","heartbeatEnabled":false, "limit": {"remaining": 300, "limit": 300, "reset": 1711929600}, "appName":"ws-feedhandler-xxxxxxxxxx-xxxxx"}

New response (after change):

{"info":"Welcome to the BitMEX Realtime API.","version":"2.0.0","timestamp":"2026-01-26T08:17:40.000Z","docs":"https://www.bitmex.com/app/wsAPI","heartbeatEnabled":false,"limit":{},"appName":"ws-feedhandler-xxxxxxxxxx-xxxxx"}

The limit sub-fields (remaining, limit, reset) will no longer be present in the message.

Who is affected?

This change affects clients or integrations that parse the limit field from the initial WebSocket connection response to manage rate limiting or connection logic. If your integration does not depend on this field, no action is required.

What action is needed?

Please review your WebSocket integration code and remove any dependency on the limit field from the message. 

This is a subtractive change — a field is being removed. Integrations that strictly validate the shape of WebSocket responses may need to be updated.

If you have any questions about these upcoming changes, please contact Support.

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