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

# HDL for builders

> Free HDL market data for perpetual futures platforms: prices, order books and candles over WebSocket and REST. Coming soon.

> [!NOTE]
>
> The HDL API is coming soon. The details on this page describe the planned
> service and may change before launch.

HDL will be available as a market data source for perpetual futures builders
and platforms, **free of charge**. Use the same book that prices fills on
Hyperprop as the reference for your own product.

## What you get

HDL data will be delivered over **WebSocket** for live streams and **REST**
for queries and history:

* **Prices**: live best bid, best ask and last price.
* **Order books**: the full HDL order book.
* **Candles**: live and historical candles.
* **Status**: whether each instrument is currently available.

Every key covers **all HDL symbols**. See [Supported markets](https://docs.hyperprop.com/hdl/markets.md).

## Access

Access is by partner API key, issued by Hyperprop.

**1. Request access**

Contact Ruby Quinn at
[ruby.hyperprop@mail.grokbot.com](mailto:ruby.hyperprop@mail.grokbot.com)
with your company, your product and how you plan to use HDL data.

**2. Receive your key**

Hyperprop issues a partner API key for your backend.

**3. Connect from your backend**

Use the key from your servers to stream and query HDL, then serve the data
to your own users.

> [!WARNING]
>
> HDL keys are for **backend-to-backend** use only. Never embed a key in a
> browser, a mobile app or any other client you distribute. Connections from
> browsers are not supported.

## Limits per key

| Limit | Value |
| - | - |
| Concurrent WebSocket connections | 5 |
| Symbols | All HDL symbols |
| REST requests | 300 per minute |

## Endpoints

Endpoint URLs, message formats and the full reference will be published in these
docs when the API launches.

> **[Want to use Hyperprop Deep Liquidity?](mailto:ruby.hyperprop@mail.grokbot.com)**
>
> Contact Ruby Quinn at [ruby.hyperprop@mail.grokbot.com](mailto:ruby.hyperprop@mail.grokbot.com).


## Related topics

- [Hyperprop Deep Liquidity (HDL)](https://docs.hyperprop.com/hdl/overview.md)
- [Changelog](https://docs.hyperprop.com/changelog.md)
- [Execution and fills](https://docs.hyperprop.com/hdl/execution.md)
- [Transparency and audit](https://docs.hyperprop.com/hdl/transparency.md)
- [Supported markets](https://docs.hyperprop.com/hdl/markets.md)


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