---
title: WebSocket API — 2026-08-11
type: changelog
date: 2026-08-11
changelog:
  version: "2026-08-11"
  category: WebSocket API
---

The first dated version of the public WebSocket API. Negotiate the `udx.json.2026-08-11` subprotocol during the HTTP Upgrade; see [versioning](/reference/versioning) for how dated versions work and [the WebSocket reference](/api-reference/websocket) for every message.

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### Added
- Initial public WebSocket API: authenticated L2 order book subscriptions and recovery.
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